formatting: drop `grey`, our custom black version stable
authorPierre-Yves David <pierre-yves.david@octobus.net>
Tue, 29 Oct 2019 11:07:25 +0100
branchstable
changeset 43348 daa3b58906d5
parent 43347 abb95b6f79d3
child 43349 c3e10f705a6c
formatting: drop `grey`, our custom black version Now that the official black has all we want, we can drop this.
black.toml
contrib/grey.py
tests/test-check-code.t
tests/test-check-format.t
tests/test-check-module-imports.t
tests/test-check-py3-compat.t
--- a/black.toml	Tue Oct 29 10:43:47 2019 +0100
+++ b/black.toml	Tue Oct 29 11:07:25 2019 +0100
@@ -11,7 +11,6 @@
 | mercurial/thirdparty/
 | hgext/fsmonitor/pywatchman/
 | contrib/python-zstandard/
-| contrib/grey.py
 '''
 skip-string-normalization = true
 quiet = true
--- a/contrib/grey.py	Tue Oct 29 10:43:47 2019 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,4094 +0,0 @@
-# no-check-code because 3rd party
-import ast
-import asyncio
-from concurrent.futures import Executor, ProcessPoolExecutor
-from contextlib import contextmanager
-from datetime import datetime
-from enum import Enum
-from functools import lru_cache, partial, wraps
-import io
-import itertools
-import logging
-from multiprocessing import Manager, freeze_support
-import os
-from pathlib import Path
-import pickle
-import re
-import signal
-import sys
-import tempfile
-import tokenize
-import traceback
-from typing import (
-    Any,
-    Callable,
-    Collection,
-    Dict,
-    Generator,
-    Generic,
-    Iterable,
-    Iterator,
-    List,
-    Optional,
-    Pattern,
-    Sequence,
-    Set,
-    Tuple,
-    TypeVar,
-    Union,
-    cast,
-)
-
-from appdirs import user_cache_dir
-from attr import dataclass, evolve, Factory
-import click
-import toml
-from typed_ast import ast3, ast27
-
-# lib2to3 fork
-from blib2to3.pytree import Node, Leaf, type_repr
-from blib2to3 import pygram, pytree
-from blib2to3.pgen2 import driver, token
-from blib2to3.pgen2.grammar import Grammar
-from blib2to3.pgen2.parse import ParseError
-
-__version__ = '19.3b1.dev95+gdc1add6.d20191005'
-
-DEFAULT_LINE_LENGTH = 88
-DEFAULT_EXCLUDES = (
-    r"/(\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|_build|buck-out|build|dist)/"
-)
-DEFAULT_INCLUDES = r"\.pyi?$"
-CACHE_DIR = Path(user_cache_dir("black", version=__version__))
-
-
-# types
-FileContent = str
-Encoding = str
-NewLine = str
-Depth = int
-NodeType = int
-LeafID = int
-Priority = int
-Index = int
-LN = Union[Leaf, Node]
-SplitFunc = Callable[["Line", Collection["Feature"]], Iterator["Line"]]
-Timestamp = float
-FileSize = int
-CacheInfo = Tuple[Timestamp, FileSize]
-Cache = Dict[Path, CacheInfo]
-out = partial(click.secho, bold=True, err=True)
-err = partial(click.secho, fg="red", err=True)
-
-pygram.initialize(CACHE_DIR)
-syms = pygram.python_symbols
-
-
-class NothingChanged(UserWarning):
-    """Raised when reformatted code is the same as source."""
-
-
-class CannotSplit(Exception):
-    """A readable split that fits the allotted line length is impossible."""
-
-
-class InvalidInput(ValueError):
-    """Raised when input source code fails all parse attempts."""
-
-
-class WriteBack(Enum):
-    NO = 0
-    YES = 1
-    DIFF = 2
-    CHECK = 3
-
-    @classmethod
-    def from_configuration(cls, *, check: bool, diff: bool) -> "WriteBack":
-        if check and not diff:
-            return cls.CHECK
-
-        return cls.DIFF if diff else cls.YES
-
-
-class Changed(Enum):
-    NO = 0
-    CACHED = 1
-    YES = 2
-
-
-class TargetVersion(Enum):
-    PY27 = 2
-    PY33 = 3
-    PY34 = 4
-    PY35 = 5
-    PY36 = 6
-    PY37 = 7
-    PY38 = 8
-
-    def is_python2(self) -> bool:
-        return self is TargetVersion.PY27
-
-
-PY36_VERSIONS = {TargetVersion.PY36, TargetVersion.PY37, TargetVersion.PY38}
-
-
-class Feature(Enum):
-    # All string literals are unicode
-    UNICODE_LITERALS = 1
-    F_STRINGS = 2
-    NUMERIC_UNDERSCORES = 3
-    TRAILING_COMMA_IN_CALL = 4
-    TRAILING_COMMA_IN_DEF = 5
-    # The following two feature-flags are mutually exclusive, and exactly one should be
-    # set for every version of python.
-    ASYNC_IDENTIFIERS = 6
-    ASYNC_KEYWORDS = 7
-    ASSIGNMENT_EXPRESSIONS = 8
-    POS_ONLY_ARGUMENTS = 9
-
-
-VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
-    TargetVersion.PY27: {Feature.ASYNC_IDENTIFIERS},
-    TargetVersion.PY33: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
-    TargetVersion.PY34: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
-    TargetVersion.PY35: {
-        Feature.UNICODE_LITERALS,
-        Feature.TRAILING_COMMA_IN_CALL,
-        Feature.ASYNC_IDENTIFIERS,
-    },
-    TargetVersion.PY36: {
-        Feature.UNICODE_LITERALS,
-        Feature.F_STRINGS,
-        Feature.NUMERIC_UNDERSCORES,
-        Feature.TRAILING_COMMA_IN_CALL,
-        Feature.TRAILING_COMMA_IN_DEF,
-        Feature.ASYNC_IDENTIFIERS,
-    },
-    TargetVersion.PY37: {
-        Feature.UNICODE_LITERALS,
-        Feature.F_STRINGS,
-        Feature.NUMERIC_UNDERSCORES,
-        Feature.TRAILING_COMMA_IN_CALL,
-        Feature.TRAILING_COMMA_IN_DEF,
-        Feature.ASYNC_KEYWORDS,
-    },
-    TargetVersion.PY38: {
-        Feature.UNICODE_LITERALS,
-        Feature.F_STRINGS,
-        Feature.NUMERIC_UNDERSCORES,
-        Feature.TRAILING_COMMA_IN_CALL,
-        Feature.TRAILING_COMMA_IN_DEF,
-        Feature.ASYNC_KEYWORDS,
-        Feature.ASSIGNMENT_EXPRESSIONS,
-        Feature.POS_ONLY_ARGUMENTS,
-    },
-}
-
-
-@dataclass
-class FileMode:
-    target_versions: Set[TargetVersion] = Factory(set)
-    line_length: int = DEFAULT_LINE_LENGTH
-    string_normalization: bool = True
-    is_pyi: bool = False
-
-    def get_cache_key(self) -> str:
-        if self.target_versions:
-            version_str = ",".join(
-                str(version.value)
-                for version in sorted(self.target_versions, key=lambda v: v.value)
-            )
-        else:
-            version_str = "-"
-        parts = [
-            version_str,
-            str(self.line_length),
-            str(int(self.string_normalization)),
-            str(int(self.is_pyi)),
-        ]
-        return ".".join(parts)
-
-
-def supports_feature(target_versions: Set[TargetVersion], feature: Feature) -> bool:
-    return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
-
-
-def read_pyproject_toml(
-    ctx: click.Context, param: click.Parameter, value: Union[str, int, bool, None]
-) -> Optional[str]:
-    """Inject Black configuration from "pyproject.toml" into defaults in `ctx`.
-
-    Returns the path to a successfully found and read configuration file, None
-    otherwise.
-    """
-    assert not isinstance(value, (int, bool)), "Invalid parameter type passed"
-    if not value:
-        root = find_project_root(ctx.params.get("src", ()))
-        path = root / "pyproject.toml"
-        if path.is_file():
-            value = str(path)
-        else:
-            return None
-
-    try:
-        pyproject_toml = toml.load(value)
-        config = pyproject_toml.get("tool", {}).get("black", {})
-    except (toml.TomlDecodeError, OSError) as e:
-        raise click.FileError(
-            filename=value, hint=f"Error reading configuration file: {e}"
-        )
-
-    if not config:
-        return None
-
-    if ctx.default_map is None:
-        ctx.default_map = {}
-    ctx.default_map.update(  # type: ignore  # bad types in .pyi
-        {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}
-    )
-    return value
-
-
-@click.command(context_settings=dict(help_option_names=["-h", "--help"]))
-@click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
-@click.option(
-    "-l",
-    "--line-length",
-    type=int,
-    default=DEFAULT_LINE_LENGTH,
-    help="How many characters per line to allow.",
-    show_default=True,
-)
-@click.option(
-    "-t",
-    "--target-version",
-    type=click.Choice([v.name.lower() for v in TargetVersion]),
-    callback=lambda c, p, v: [TargetVersion[val.upper()] for val in v],
-    multiple=True,
-    help=(
-        "Python versions that should be supported by Black's output. [default: "
-        "per-file auto-detection]"
-    ),
-)
-@click.option(
-    "--py36",
-    is_flag=True,
-    help=(
-        "Allow using Python 3.6-only syntax on all input files.  This will put "
-        "trailing commas in function signatures and calls also after *args and "
-        "**kwargs. Deprecated; use --target-version instead. "
-        "[default: per-file auto-detection]"
-    ),
-)
-@click.option(
-    "--pyi",
-    is_flag=True,
-    help=(
-        "Format all input files like typing stubs regardless of file extension "
-        "(useful when piping source on standard input)."
-    ),
-)
-@click.option(
-    "-S",
-    "--skip-string-normalization",
-    is_flag=True,
-    help="Don't normalize string quotes or prefixes.",
-)
-@click.option(
-    "--check",
-    is_flag=True,
-    help=(
-        "Don't write the files back, just return the status.  Return code 0 "
-        "means nothing would change.  Return code 1 means some files would be "
-        "reformatted.  Return code 123 means there was an internal error."
-    ),
-)
-@click.option(
-    "--diff",
-    is_flag=True,
-    help="Don't write the files back, just output a diff for each file on stdout.",
-)
-@click.option(
-    "--fast/--safe",
-    is_flag=True,
-    help="If --fast given, skip temporary sanity checks. [default: --safe]",
-)
-@click.option(
-    "--include",
-    type=str,
-    default=DEFAULT_INCLUDES,
-    help=(
-        "A regular expression that matches files and directories that should be "
-        "included on recursive searches.  An empty value means all files are "
-        "included regardless of the name.  Use forward slashes for directories on "
-        "all platforms (Windows, too).  Exclusions are calculated first, inclusions "
-        "later."
-    ),
-    show_default=True,
-)
-@click.option(
-    "--exclude",
-    type=str,
-    default=DEFAULT_EXCLUDES,
-    help=(
-        "A regular expression that matches files and directories that should be "
-        "excluded on recursive searches.  An empty value means no paths are excluded. "
-        "Use forward slashes for directories on all platforms (Windows, too).  "
-        "Exclusions are calculated first, inclusions later."
-    ),
-    show_default=True,
-)
-@click.option(
-    "-q",
-    "--quiet",
-    is_flag=True,
-    help=(
-        "Don't emit non-error messages to stderr. Errors are still emitted; "
-        "silence those with 2>/dev/null."
-    ),
-)
-@click.option(
-    "-v",
-    "--verbose",
-    is_flag=True,
-    help=(
-        "Also emit messages to stderr about files that were not changed or were "
-        "ignored due to --exclude=."
-    ),
-)
-@click.version_option(version=__version__)
-@click.argument(
-    "src",
-    nargs=-1,
-    type=click.Path(
-        exists=True, file_okay=True, dir_okay=True, readable=True, allow_dash=True
-    ),
-    is_eager=True,
-)
-@click.option(
-    "--config",
-    type=click.Path(
-        exists=False, file_okay=True, dir_okay=False, readable=True, allow_dash=False
-    ),
-    is_eager=True,
-    callback=read_pyproject_toml,
-    help="Read configuration from PATH.",
-)
-@click.pass_context
-def main(
-    ctx: click.Context,
-    code: Optional[str],
-    line_length: int,
-    target_version: List[TargetVersion],
-    check: bool,
-    diff: bool,
-    fast: bool,
-    pyi: bool,
-    py36: bool,
-    skip_string_normalization: bool,
-    quiet: bool,
-    verbose: bool,
-    include: str,
-    exclude: str,
-    src: Tuple[str],
-    config: Optional[str],
-) -> None:
-    """The uncompromising code formatter."""
-    write_back = WriteBack.from_configuration(check=check, diff=diff)
-    if target_version:
-        if py36:
-            err(f"Cannot use both --target-version and --py36")
-            ctx.exit(2)
-        else:
-            versions = set(target_version)
-    elif py36:
-        err(
-            "--py36 is deprecated and will be removed in a future version. "
-            "Use --target-version py36 instead."
-        )
-        versions = PY36_VERSIONS
-    else:
-        # We'll autodetect later.
-        versions = set()
-    mode = FileMode(
-        target_versions=versions,
-        line_length=line_length,
-        is_pyi=pyi,
-        string_normalization=not skip_string_normalization,
-    )
-    if config and verbose:
-        out(f"Using configuration from {config}.", bold=False, fg="blue")
-    if code is not None:
-        print(format_str(code, mode=mode))
-        ctx.exit(0)
-    try:
-        include_regex = re_compile_maybe_verbose(include)
-    except re.error:
-        err(f"Invalid regular expression for include given: {include!r}")
-        ctx.exit(2)
-    try:
-        exclude_regex = re_compile_maybe_verbose(exclude)
-    except re.error:
-        err(f"Invalid regular expression for exclude given: {exclude!r}")
-        ctx.exit(2)
-    report = Report(check=check, quiet=quiet, verbose=verbose)
-    root = find_project_root(src)
-    sources: Set[Path] = set()
-    path_empty(src, quiet, verbose, ctx)
-    for s in src:
-        p = Path(s)
-        if p.is_dir():
-            sources.update(
-                gen_python_files_in_dir(p, root, include_regex, exclude_regex, report)
-            )
-        elif p.is_file() or s == "-":
-            # if a file was explicitly given, we don't care about its extension
-            sources.add(p)
-        else:
-            err(f"invalid path: {s}")
-    if len(sources) == 0:
-        if verbose or not quiet:
-            out("No Python files are present to be formatted. Nothing to do 😴")
-        ctx.exit(0)
-
-    if len(sources) == 1:
-        reformat_one(
-            src=sources.pop(),
-            fast=fast,
-            write_back=write_back,
-            mode=mode,
-            report=report,
-        )
-    else:
-        reformat_many(
-            sources=sources, fast=fast, write_back=write_back, mode=mode, report=report
-        )
-
-    if verbose or not quiet:
-        out("Oh no! 💥 💔 💥" if report.return_code else "All done! ✨ 🍰 ✨")
-        click.secho(str(report), err=True)
-    ctx.exit(report.return_code)
-
-
-def path_empty(src: Tuple[str], quiet: bool, verbose: bool, ctx: click.Context) -> None:
-    """
-    Exit if there is no `src` provided for formatting
-    """
-    if not src:
-        if verbose or not quiet:
-            out("No Path provided. Nothing to do 😴")
-            ctx.exit(0)
-
-
-def reformat_one(
-    src: Path, fast: bool, write_back: WriteBack, mode: FileMode, report: "Report"
-) -> None:
-    """Reformat a single file under `src` without spawning child processes.
-
-    `fast`, `write_back`, and `mode` options are passed to
-    :func:`format_file_in_place` or :func:`format_stdin_to_stdout`.
-    """
-    try:
-        changed = Changed.NO
-        if not src.is_file() and str(src) == "-":
-            if format_stdin_to_stdout(fast=fast, write_back=write_back, mode=mode):
-                changed = Changed.YES
-        else:
-            cache: Cache = {}
-            if write_back != WriteBack.DIFF:
-                cache = read_cache(mode)
-                res_src = src.resolve()
-                if res_src in cache and cache[res_src] == get_cache_info(res_src):
-                    changed = Changed.CACHED
-            if changed is not Changed.CACHED and format_file_in_place(
-                src, fast=fast, write_back=write_back, mode=mode
-            ):
-                changed = Changed.YES
-            if (write_back is WriteBack.YES and changed is not Changed.CACHED) or (
-                write_back is WriteBack.CHECK and changed is Changed.NO
-            ):
-                write_cache(cache, [src], mode)
-        report.done(src, changed)
-    except Exception as exc:
-        report.failed(src, str(exc))
-
-
-def reformat_many(
-    sources: Set[Path],
-    fast: bool,
-    write_back: WriteBack,
-    mode: FileMode,
-    report: "Report",
-) -> None:
-    """Reformat multiple files using a ProcessPoolExecutor."""
-    loop = asyncio.get_event_loop()
-    worker_count = os.cpu_count()
-    if sys.platform == "win32":
-        # Work around https://bugs.python.org/issue26903
-        worker_count = min(worker_count, 61)
-    executor = ProcessPoolExecutor(max_workers=worker_count)
-    try:
-        loop.run_until_complete(
-            schedule_formatting(
-                sources=sources,
-                fast=fast,
-                write_back=write_back,
-                mode=mode,
-                report=report,
-                loop=loop,
-                executor=executor,
-            )
-        )
-    finally:
-        shutdown(loop)
-        executor.shutdown()
-
-
-async def schedule_formatting(
-    sources: Set[Path],
-    fast: bool,
-    write_back: WriteBack,
-    mode: FileMode,
-    report: "Report",
-    loop: asyncio.AbstractEventLoop,
-    executor: Executor,
-) -> None:
-    """Run formatting of `sources` in parallel using the provided `executor`.
-
-    (Use ProcessPoolExecutors for actual parallelism.)
-
-    `write_back`, `fast`, and `mode` options are passed to
-    :func:`format_file_in_place`.
-    """
-    cache: Cache = {}
-    if write_back != WriteBack.DIFF:
-        cache = read_cache(mode)
-        sources, cached = filter_cached(cache, sources)
-        for src in sorted(cached):
-            report.done(src, Changed.CACHED)
-    if not sources:
-        return
-
-    cancelled = []
-    sources_to_cache = []
-    lock = None
-    if write_back == WriteBack.DIFF:
-        # For diff output, we need locks to ensure we don't interleave output
-        # from different processes.
-        manager = Manager()
-        lock = manager.Lock()
-    tasks = {
-        asyncio.ensure_future(
-            loop.run_in_executor(
-                executor, format_file_in_place, src, fast, mode, write_back, lock
-            )
-        ): src
-        for src in sorted(sources)
-    }
-    pending: Iterable[asyncio.Future] = tasks.keys()
-    try:
-        loop.add_signal_handler(signal.SIGINT, cancel, pending)
-        loop.add_signal_handler(signal.SIGTERM, cancel, pending)
-    except NotImplementedError:
-        # There are no good alternatives for these on Windows.
-        pass
-    while pending:
-        done, _ = await asyncio.wait(pending, return_when=asyncio.FIRST_COMPLETED)
-        for task in done:
-            src = tasks.pop(task)
-            if task.cancelled():
-                cancelled.append(task)
-            elif task.exception():
-                report.failed(src, str(task.exception()))
-            else:
-                changed = Changed.YES if task.result() else Changed.NO
-                # If the file was written back or was successfully checked as
-                # well-formatted, store this information in the cache.
-                if write_back is WriteBack.YES or (
-                    write_back is WriteBack.CHECK and changed is Changed.NO
-                ):
-                    sources_to_cache.append(src)
-                report.done(src, changed)
-    if cancelled:
-        await asyncio.gather(*cancelled, loop=loop, return_exceptions=True)
-    if sources_to_cache:
-        write_cache(cache, sources_to_cache, mode)
-
-
-def format_file_in_place(
-    src: Path,
-    fast: bool,
-    mode: FileMode,
-    write_back: WriteBack = WriteBack.NO,
-    lock: Any = None,  # multiprocessing.Manager().Lock() is some crazy proxy
-) -> bool:
-    """Format file under `src` path. Return True if changed.
-
-    If `write_back` is DIFF, write a diff to stdout. If it is YES, write reformatted
-    code to the file.
-    `mode` and `fast` options are passed to :func:`format_file_contents`.
-    """
-    if src.suffix == ".pyi":
-        mode = evolve(mode, is_pyi=True)
-
-    then = datetime.utcfromtimestamp(src.stat().st_mtime)
-    with open(src, "rb") as buf:
-        src_contents, encoding, newline = decode_bytes(buf.read())
-    try:
-        dst_contents = format_file_contents(src_contents, fast=fast, mode=mode)
-    except NothingChanged:
-        return False
-
-    if write_back == write_back.YES:
-        with open(src, "w", encoding=encoding, newline=newline) as f:
-            f.write(dst_contents)
-    elif write_back == write_back.DIFF:
-        now = datetime.utcnow()
-        src_name = f"{src}\t{then} +0000"
-        dst_name = f"{src}\t{now} +0000"
-        diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
-
-        with lock or nullcontext():
-            f = io.TextIOWrapper(
-                sys.stdout.buffer,
-                encoding=encoding,
-                newline=newline,
-                write_through=True,
-            )
-            f.write(diff_contents)
-            f.detach()
-
-    return True
-
-
-def format_stdin_to_stdout(
-    fast: bool, *, write_back: WriteBack = WriteBack.NO, mode: FileMode
-) -> bool:
-    """Format file on stdin. Return True if changed.
-
-    If `write_back` is YES, write reformatted code back to stdout. If it is DIFF,
-    write a diff to stdout. The `mode` argument is passed to
-    :func:`format_file_contents`.
-    """
-    then = datetime.utcnow()
-    src, encoding, newline = decode_bytes(sys.stdin.buffer.read())
-    dst = src
-    try:
-        dst = format_file_contents(src, fast=fast, mode=mode)
-        return True
-
-    except NothingChanged:
-        return False
-
-    finally:
-        f = io.TextIOWrapper(
-            sys.stdout.buffer, encoding=encoding, newline=newline, write_through=True
-        )
-        if write_back == WriteBack.YES:
-            f.write(dst)
-        elif write_back == WriteBack.DIFF:
-            now = datetime.utcnow()
-            src_name = f"STDIN\t{then} +0000"
-            dst_name = f"STDOUT\t{now} +0000"
-            f.write(diff(src, dst, src_name, dst_name))
-        f.detach()
-
-
-def format_file_contents(
-    src_contents: str, *, fast: bool, mode: FileMode
-) -> FileContent:
-    """Reformat contents a file and return new contents.
-
-    If `fast` is False, additionally confirm that the reformatted code is
-    valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it.
-    `mode` is passed to :func:`format_str`.
-    """
-    if src_contents.strip() == "":
-        raise NothingChanged
-
-    dst_contents = format_str(src_contents, mode=mode)
-    if src_contents == dst_contents:
-        raise NothingChanged
-
-    if not fast:
-        assert_equivalent(src_contents, dst_contents)
-        assert_stable(src_contents, dst_contents, mode=mode)
-    return dst_contents
-
-
-def format_str(src_contents: str, *, mode: FileMode) -> FileContent:
-    """Reformat a string and return new contents.
-
-    `mode` determines formatting options, such as how many characters per line are
-    allowed.
-    """
-    src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
-    dst_contents = []
-    future_imports = get_future_imports(src_node)
-    if mode.target_versions:
-        versions = mode.target_versions
-    else:
-        versions = detect_target_versions(src_node)
-    normalize_fmt_off(src_node)
-    lines = LineGenerator(
-        remove_u_prefix="unicode_literals" in future_imports
-        or supports_feature(versions, Feature.UNICODE_LITERALS),
-        is_pyi=mode.is_pyi,
-        normalize_strings=mode.string_normalization,
-    )
-    elt = EmptyLineTracker(is_pyi=mode.is_pyi)
-    empty_line = Line()
-    after = 0
-    split_line_features = {
-        feature
-        for feature in {Feature.TRAILING_COMMA_IN_CALL, Feature.TRAILING_COMMA_IN_DEF}
-        if supports_feature(versions, feature)
-    }
-    for current_line in lines.visit(src_node):
-        for _ in range(after):
-            dst_contents.append(str(empty_line))
-        before, after = elt.maybe_empty_lines(current_line)
-        for _ in range(before):
-            dst_contents.append(str(empty_line))
-        for line in split_line(
-            current_line, line_length=mode.line_length, features=split_line_features
-        ):
-            dst_contents.append(str(line))
-    return "".join(dst_contents)
-
-
-def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
-    """Return a tuple of (decoded_contents, encoding, newline).
-
-    `newline` is either CRLF or LF but `decoded_contents` is decoded with
-    universal newlines (i.e. only contains LF).
-    """
-    srcbuf = io.BytesIO(src)
-    encoding, lines = tokenize.detect_encoding(srcbuf.readline)
-    if not lines:
-        return "", encoding, "\n"
-
-    newline = "\r\n" if b"\r\n" == lines[0][-2:] else "\n"
-    srcbuf.seek(0)
-    with io.TextIOWrapper(srcbuf, encoding) as tiow:
-        return tiow.read(), encoding, newline
-
-
-def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
-    if not target_versions:
-        # No target_version specified, so try all grammars.
-        return [
-            # Python 3.7+
-            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,
-            # Python 3.0-3.6
-            pygram.python_grammar_no_print_statement_no_exec_statement,
-            # Python 2.7 with future print_function import
-            pygram.python_grammar_no_print_statement,
-            # Python 2.7
-            pygram.python_grammar,
-        ]
-    elif all(version.is_python2() for version in target_versions):
-        # Python 2-only code, so try Python 2 grammars.
-        return [
-            # Python 2.7 with future print_function import
-            pygram.python_grammar_no_print_statement,
-            # Python 2.7
-            pygram.python_grammar,
-        ]
-    else:
-        # Python 3-compatible code, so only try Python 3 grammar.
-        grammars = []
-        # If we have to parse both, try to parse async as a keyword first
-        if not supports_feature(target_versions, Feature.ASYNC_IDENTIFIERS):
-            # Python 3.7+
-            grammars.append(
-                pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords  # noqa: B950
-            )
-        if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):
-            # Python 3.0-3.6
-            grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)
-        # At least one of the above branches must have been taken, because every Python
-        # version has exactly one of the two 'ASYNC_*' flags
-        return grammars
-
-
-def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:
-    """Given a string with source, return the lib2to3 Node."""
-    if src_txt[-1:] != "\n":
-        src_txt += "\n"
-
-    for grammar in get_grammars(set(target_versions)):
-        drv = driver.Driver(grammar, pytree.convert)
-        try:
-            result = drv.parse_string(src_txt, True)
-            break
-
-        except ParseError as pe:
-            lineno, column = pe.context[1]
-            lines = src_txt.splitlines()
-            try:
-                faulty_line = lines[lineno - 1]
-            except IndexError:
-                faulty_line = "<line number missing in source>"
-            exc = InvalidInput(f"Cannot parse: {lineno}:{column}: {faulty_line}")
-    else:
-        raise exc from None
-
-    if isinstance(result, Leaf):
-        result = Node(syms.file_input, [result])
-    return result
-
-
-def lib2to3_unparse(node: Node) -> str:
-    """Given a lib2to3 node, return its string representation."""
-    code = str(node)
-    return code
-
-
-T = TypeVar("T")
-
-
-class Visitor(Generic[T]):
-    """Basic lib2to3 visitor that yields things of type `T` on `visit()`."""
-
-    def visit(self, node: LN) -> Iterator[T]:
-        """Main method to visit `node` and its children.
-
-        It tries to find a `visit_*()` method for the given `node.type`, like
-        `visit_simple_stmt` for Node objects or `visit_INDENT` for Leaf objects.
-        If no dedicated `visit_*()` method is found, chooses `visit_default()`
-        instead.
-
-        Then yields objects of type `T` from the selected visitor.
-        """
-        if node.type < 256:
-            name = token.tok_name[node.type]
-        else:
-            name = type_repr(node.type)
-        yield from getattr(self, f"visit_{name}", self.visit_default)(node)
-
-    def visit_default(self, node: LN) -> Iterator[T]:
-        """Default `visit_*()` implementation. Recurses to children of `node`."""
-        if isinstance(node, Node):
-            for child in node.children:
-                yield from self.visit(child)
-
-
-@dataclass
-class DebugVisitor(Visitor[T]):
-    tree_depth: int = 0
-
-    def visit_default(self, node: LN) -> Iterator[T]:
-        indent = " " * (2 * self.tree_depth)
-        if isinstance(node, Node):
-            _type = type_repr(node.type)
-            out(f"{indent}{_type}", fg="yellow")
-            self.tree_depth += 1
-            for child in node.children:
-                yield from self.visit(child)
-
-            self.tree_depth -= 1
-            out(f"{indent}/{_type}", fg="yellow", bold=False)
-        else:
-            _type = token.tok_name.get(node.type, str(node.type))
-            out(f"{indent}{_type}", fg="blue", nl=False)
-            if node.prefix:
-                # We don't have to handle prefixes for `Node` objects since
-                # that delegates to the first child anyway.
-                out(f" {node.prefix!r}", fg="green", bold=False, nl=False)
-            out(f" {node.value!r}", fg="blue", bold=False)
-
-    @classmethod
-    def show(cls, code: Union[str, Leaf, Node]) -> None:
-        """Pretty-print the lib2to3 AST of a given string of `code`.
-
-        Convenience method for debugging.
-        """
-        v: DebugVisitor[None] = DebugVisitor()
-        if isinstance(code, str):
-            code = lib2to3_parse(code)
-        list(v.visit(code))
-
-
-WHITESPACE = {token.DEDENT, token.INDENT, token.NEWLINE}
-STATEMENT = {
-    syms.if_stmt,
-    syms.while_stmt,
-    syms.for_stmt,
-    syms.try_stmt,
-    syms.except_clause,
-    syms.with_stmt,
-    syms.funcdef,
-    syms.classdef,
-}
-STANDALONE_COMMENT = 153
-token.tok_name[STANDALONE_COMMENT] = "STANDALONE_COMMENT"
-LOGIC_OPERATORS = {"and", "or"}
-COMPARATORS = {
-    token.LESS,
-    token.GREATER,
-    token.EQEQUAL,
-    token.NOTEQUAL,
-    token.LESSEQUAL,
-    token.GREATEREQUAL,
-}
-MATH_OPERATORS = {
-    token.VBAR,
-    token.CIRCUMFLEX,
-    token.AMPER,
-    token.LEFTSHIFT,
-    token.RIGHTSHIFT,
-    token.PLUS,
-    token.MINUS,
-    token.STAR,
-    token.SLASH,
-    token.DOUBLESLASH,
-    token.PERCENT,
-    token.AT,
-    token.TILDE,
-    token.DOUBLESTAR,
-}
-STARS = {token.STAR, token.DOUBLESTAR}
-VARARGS_SPECIALS = STARS | {token.SLASH}
-VARARGS_PARENTS = {
-    syms.arglist,
-    syms.argument,  # double star in arglist
-    syms.trailer,  # single argument to call
-    syms.typedargslist,
-    syms.varargslist,  # lambdas
-}
-UNPACKING_PARENTS = {
-    syms.atom,  # single element of a list or set literal
-    syms.dictsetmaker,
-    syms.listmaker,
-    syms.testlist_gexp,
-    syms.testlist_star_expr,
-}
-TEST_DESCENDANTS = {
-    syms.test,
-    syms.lambdef,
-    syms.or_test,
-    syms.and_test,
-    syms.not_test,
-    syms.comparison,
-    syms.star_expr,
-    syms.expr,
-    syms.xor_expr,
-    syms.and_expr,
-    syms.shift_expr,
-    syms.arith_expr,
-    syms.trailer,
-    syms.term,
-    syms.power,
-}
-ASSIGNMENTS = {
-    "=",
-    "+=",
-    "-=",
-    "*=",
-    "@=",
-    "/=",
-    "%=",
-    "&=",
-    "|=",
-    "^=",
-    "<<=",
-    ">>=",
-    "**=",
-    "//=",
-}
-COMPREHENSION_PRIORITY = 20
-COMMA_PRIORITY = 18
-TERNARY_PRIORITY = 16
-LOGIC_PRIORITY = 14
-STRING_PRIORITY = 12
-COMPARATOR_PRIORITY = 10
-MATH_PRIORITIES = {
-    token.VBAR: 9,
-    token.CIRCUMFLEX: 8,
-    token.AMPER: 7,
-    token.LEFTSHIFT: 6,
-    token.RIGHTSHIFT: 6,
-    token.PLUS: 5,
-    token.MINUS: 5,
-    token.STAR: 4,
-    token.SLASH: 4,
-    token.DOUBLESLASH: 4,
-    token.PERCENT: 4,
-    token.AT: 4,
-    token.TILDE: 3,
-    token.DOUBLESTAR: 2,
-}
-DOT_PRIORITY = 1
-
-
-@dataclass
-class BracketTracker:
-    """Keeps track of brackets on a line."""
-
-    depth: int = 0
-    bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = Factory(dict)
-    delimiters: Dict[LeafID, Priority] = Factory(dict)
-    previous: Optional[Leaf] = None
-    _for_loop_depths: List[int] = Factory(list)
-    _lambda_argument_depths: List[int] = Factory(list)
-
-    def mark(self, leaf: Leaf) -> None:
-        """Mark `leaf` with bracket-related metadata. Keep track of delimiters.
-
-        All leaves receive an int `bracket_depth` field that stores how deep
-        within brackets a given leaf is. 0 means there are no enclosing brackets
-        that started on this line.
-
-        If a leaf is itself a closing bracket, it receives an `opening_bracket`
-        field that it forms a pair with. This is a one-directional link to
-        avoid reference cycles.
-
-        If a leaf is a delimiter (a token on which Black can split the line if
-        needed) and it's on depth 0, its `id()` is stored in the tracker's
-        `delimiters` field.
-        """
-        if leaf.type == token.COMMENT:
-            return
-
-        self.maybe_decrement_after_for_loop_variable(leaf)
-        self.maybe_decrement_after_lambda_arguments(leaf)
-        if leaf.type in CLOSING_BRACKETS:
-            self.depth -= 1
-            opening_bracket = self.bracket_match.pop((self.depth, leaf.type))
-            leaf.opening_bracket = opening_bracket
-        leaf.bracket_depth = self.depth
-        if self.depth == 0:
-            delim = is_split_before_delimiter(leaf, self.previous)
-            if delim and self.previous is not None:
-                self.delimiters[id(self.previous)] = delim
-            else:
-                delim = is_split_after_delimiter(leaf, self.previous)
-                if delim:
-                    self.delimiters[id(leaf)] = delim
-        if leaf.type in OPENING_BRACKETS:
-            self.bracket_match[self.depth, BRACKET[leaf.type]] = leaf
-            self.depth += 1
-        self.previous = leaf
-        self.maybe_increment_lambda_arguments(leaf)
-        self.maybe_increment_for_loop_variable(leaf)
-
-    def any_open_brackets(self) -> bool:
-        """Return True if there is an yet unmatched open bracket on the line."""
-        return bool(self.bracket_match)
-
-    def max_delimiter_priority(self, exclude: Iterable[LeafID] = ()) -> Priority:
-        """Return the highest priority of a delimiter found on the line.
-
-        Values are consistent with what `is_split_*_delimiter()` return.
-        Raises ValueError on no delimiters.
-        """
-        return max(v for k, v in self.delimiters.items() if k not in exclude)
-
-    def delimiter_count_with_priority(self, priority: Priority = 0) -> int:
-        """Return the number of delimiters with the given `priority`.
-
-        If no `priority` is passed, defaults to max priority on the line.
-        """
-        if not self.delimiters:
-            return 0
-
-        priority = priority or self.max_delimiter_priority()
-        return sum(1 for p in self.delimiters.values() if p == priority)
-
-    def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool:
-        """In a for loop, or comprehension, the variables are often unpacks.
-
-        To avoid splitting on the comma in this situation, increase the depth of
-        tokens between `for` and `in`.
-        """
-        if leaf.type == token.NAME and leaf.value == "for":
-            self.depth += 1
-            self._for_loop_depths.append(self.depth)
-            return True
-
-        return False
-
-    def maybe_decrement_after_for_loop_variable(self, leaf: Leaf) -> bool:
-        """See `maybe_increment_for_loop_variable` above for explanation."""
-        if (
-            self._for_loop_depths
-            and self._for_loop_depths[-1] == self.depth
-            and leaf.type == token.NAME
-            and leaf.value == "in"
-        ):
-            self.depth -= 1
-            self._for_loop_depths.pop()
-            return True
-
-        return False
-
-    def maybe_increment_lambda_arguments(self, leaf: Leaf) -> bool:
-        """In a lambda expression, there might be more than one argument.
-
-        To avoid splitting on the comma in this situation, increase the depth of
-        tokens between `lambda` and `:`.
-        """
-        if leaf.type == token.NAME and leaf.value == "lambda":
-            self.depth += 1
-            self._lambda_argument_depths.append(self.depth)
-            return True
-
-        return False
-
-    def maybe_decrement_after_lambda_arguments(self, leaf: Leaf) -> bool:
-        """See `maybe_increment_lambda_arguments` above for explanation."""
-        if (
-            self._lambda_argument_depths
-            and self._lambda_argument_depths[-1] == self.depth
-            and leaf.type == token.COLON
-        ):
-            self.depth -= 1
-            self._lambda_argument_depths.pop()
-            return True
-
-        return False
-
-    def get_open_lsqb(self) -> Optional[Leaf]:
-        """Return the most recent opening square bracket (if any)."""
-        return self.bracket_match.get((self.depth - 1, token.RSQB))
-
-
-@dataclass
-class Line:
-    """Holds leaves and comments. Can be printed with `str(line)`."""
-
-    depth: int = 0
-    leaves: List[Leaf] = Factory(list)
-    comments: Dict[LeafID, List[Leaf]] = Factory(dict)  # keys ordered like `leaves`
-    bracket_tracker: BracketTracker = Factory(BracketTracker)
-    inside_brackets: bool = False
-    should_explode: bool = False
-
-    def append(self, leaf: Leaf, preformatted: bool = False) -> None:
-        """Add a new `leaf` to the end of the line.
-
-        Unless `preformatted` is True, the `leaf` will receive a new consistent
-        whitespace prefix and metadata applied by :class:`BracketTracker`.
-        Trailing commas are maybe removed, unpacked for loop variables are
-        demoted from being delimiters.
-
-        Inline comments are put aside.
-        """
-        has_value = leaf.type in BRACKETS or bool(leaf.value.strip())
-        if not has_value:
-            return
-
-        if token.COLON == leaf.type and self.is_class_paren_empty:
-            del self.leaves[-2:]
-        if self.leaves and not preformatted:
-            # Note: at this point leaf.prefix should be empty except for
-            # imports, for which we only preserve newlines.
-            leaf.prefix += whitespace(
-                leaf, complex_subscript=self.is_complex_subscript(leaf)
-            )
-        if self.inside_brackets or not preformatted:
-            self.bracket_tracker.mark(leaf)
-            self.maybe_remove_trailing_comma(leaf)
-        if not self.append_comment(leaf):
-            self.leaves.append(leaf)
-
-    def append_safe(self, leaf: Leaf, preformatted: bool = False) -> None:
-        """Like :func:`append()` but disallow invalid standalone comment structure.
-
-        Raises ValueError when any `leaf` is appended after a standalone comment
-        or when a standalone comment is not the first leaf on the line.
-        """
-        if self.bracket_tracker.depth == 0:
-            if self.is_comment:
-                raise ValueError("cannot append to standalone comments")
-
-            if self.leaves and leaf.type == STANDALONE_COMMENT:
-                raise ValueError(
-                    "cannot append standalone comments to a populated line"
-                )
-
-        self.append(leaf, preformatted=preformatted)
-
-    @property
-    def is_comment(self) -> bool:
-        """Is this line a standalone comment?"""
-        return len(self.leaves) == 1 and self.leaves[0].type == STANDALONE_COMMENT
-
-    @property
-    def is_decorator(self) -> bool:
-        """Is this line a decorator?"""
-        return bool(self) and self.leaves[0].type == token.AT
-
-    @property
-    def is_import(self) -> bool:
-        """Is this an import line?"""
-        return bool(self) and is_import(self.leaves[0])
-
-    @property
-    def is_class(self) -> bool:
-        """Is this line a class definition?"""
-        return (
-            bool(self)
-            and self.leaves[0].type == token.NAME
-            and self.leaves[0].value == "class"
-        )
-
-    @property
-    def is_stub_class(self) -> bool:
-        """Is this line a class definition with a body consisting only of "..."?"""
-        return self.is_class and self.leaves[-3:] == [
-            Leaf(token.DOT, ".") for _ in range(3)
-        ]
-
-    @property
-    def is_collection_with_optional_trailing_comma(self) -> bool:
-        """Is this line a collection literal with a trailing comma that's optional?
-
-        Note that the trailing comma in a 1-tuple is not optional.
-        """
-        if not self.leaves or len(self.leaves) < 4:
-            return False
-        # Look for and address a trailing colon.
-        if self.leaves[-1].type == token.COLON:
-            closer = self.leaves[-2]
-            close_index = -2
-        else:
-            closer = self.leaves[-1]
-            close_index = -1
-        if closer.type not in CLOSING_BRACKETS or self.inside_brackets:
-            return False
-        if closer.type == token.RPAR:
-            # Tuples require an extra check, because if there's only
-            # one element in the tuple removing the comma unmakes the
-            # tuple.
-            #
-            # We also check for parens before looking for the trailing
-            # comma because in some cases (eg assigning a dict
-            # literal) the literal gets wrapped in temporary parens
-            # during parsing. This case is covered by the
-            # collections.py test data.
-            opener = closer.opening_bracket
-            for _open_index, leaf in enumerate(self.leaves):
-                if leaf is opener:
-                    break
-            else:
-                # Couldn't find the matching opening paren, play it safe.
-                return False
-            commas = 0
-            comma_depth = self.leaves[close_index - 1].bracket_depth
-            for leaf in self.leaves[_open_index + 1 : close_index]:
-                if leaf.bracket_depth == comma_depth and leaf.type == token.COMMA:
-                    commas += 1
-            if commas > 1:
-                # We haven't looked yet for the trailing comma because
-                # we might also have caught noop parens.
-                return self.leaves[close_index - 1].type == token.COMMA
-            elif commas == 1:
-                return False  # it's either a one-tuple or didn't have a trailing comma
-            if self.leaves[close_index - 1].type in CLOSING_BRACKETS:
-                close_index -= 1
-                closer = self.leaves[close_index]
-                if closer.type == token.RPAR:
-                    # TODO: this is a gut feeling. Will we ever see this?
-                    return False
-        if self.leaves[close_index - 1].type != token.COMMA:
-            return False
-        return True
-
-    @property
-    def is_def(self) -> bool:
-        """Is this a function definition? (Also returns True for async defs.)"""
-        try:
-            first_leaf = self.leaves[0]
-        except IndexError:
-            return False
-
-        try:
-            second_leaf: Optional[Leaf] = self.leaves[1]
-        except IndexError:
-            second_leaf = None
-        return (first_leaf.type == token.NAME and first_leaf.value == "def") or (
-            first_leaf.type == token.ASYNC
-            and second_leaf is not None
-            and second_leaf.type == token.NAME
-            and second_leaf.value == "def"
-        )
-
-    @property
-    def is_class_paren_empty(self) -> bool:
-        """Is this a class with no base classes but using parentheses?
-
-        Those are unnecessary and should be removed.
-        """
-        return (
-            bool(self)
-            and len(self.leaves) == 4
-            and self.is_class
-            and self.leaves[2].type == token.LPAR
-            and self.leaves[2].value == "("
-            and self.leaves[3].type == token.RPAR
-            and self.leaves[3].value == ")"
-        )
-
-    @property
-    def is_triple_quoted_string(self) -> bool:
-        """Is the line a triple quoted string?"""
-        return (
-            bool(self)
-            and self.leaves[0].type == token.STRING
-            and self.leaves[0].value.startswith(('"""', "'''"))
-        )
-
-    def contains_standalone_comments(self, depth_limit: int = sys.maxsize) -> bool:
-        """If so, needs to be split before emitting."""
-        for leaf in self.leaves:
-            if leaf.type == STANDALONE_COMMENT:
-                if leaf.bracket_depth <= depth_limit:
-                    return True
-        return False
-
-    def contains_uncollapsable_type_comments(self) -> bool:
-        ignored_ids = set()
-        try:
-            last_leaf = self.leaves[-1]
-            ignored_ids.add(id(last_leaf))
-            if last_leaf.type == token.COMMA or (
-                last_leaf.type == token.RPAR and not last_leaf.value
-            ):
-                # When trailing commas or optional parens are inserted by Black for
-                # consistency, comments after the previous last element are not moved
-                # (they don't have to, rendering will still be correct).  So we ignore
-                # trailing commas and invisible.
-                last_leaf = self.leaves[-2]
-                ignored_ids.add(id(last_leaf))
-        except IndexError:
-            return False
-
-        # A type comment is uncollapsable if it is attached to a leaf
-        # that isn't at the end of the line (since that could cause it
-        # to get associated to a different argument) or if there are
-        # comments before it (since that could cause it to get hidden
-        # behind a comment.
-        comment_seen = False
-        for leaf_id, comments in self.comments.items():
-            for comment in comments:
-                if is_type_comment(comment):
-                    if leaf_id not in ignored_ids or comment_seen:
-                        return True
-
-            comment_seen = True
-
-        return False
-
-    def contains_unsplittable_type_ignore(self) -> bool:
-        if not self.leaves:
-            return False
-
-        # If a 'type: ignore' is attached to the end of a line, we
-        # can't split the line, because we can't know which of the
-        # subexpressions the ignore was meant to apply to.
-        #
-        # We only want this to apply to actual physical lines from the
-        # original source, though: we don't want the presence of a
-        # 'type: ignore' at the end of a multiline expression to
-        # justify pushing it all onto one line. Thus we
-        # (unfortunately) need to check the actual source lines and
-        # only report an unsplittable 'type: ignore' if this line was
-        # one line in the original code.
-        if self.leaves[0].lineno == self.leaves[-1].lineno:
-            for comment in self.comments.get(id(self.leaves[-1]), []):
-                if is_type_comment(comment, " ignore"):
-                    return True
-
-        return False
-
-    def contains_multiline_strings(self) -> bool:
-        for leaf in self.leaves:
-            if is_multiline_string(leaf):
-                return True
-
-        return False
-
-    def maybe_remove_trailing_comma(self, closing: Leaf) -> bool:
-        """Remove trailing comma if there is one and it's safe."""
-        if not (self.leaves and self.leaves[-1].type == token.COMMA):
-            return False
-        # We remove trailing commas only in the case of importing a
-        # single name from a module.
-        if not (
-            self.leaves
-            and self.is_import
-            and len(self.leaves) > 4
-            and self.leaves[-1].type == token.COMMA
-            and closing.type in CLOSING_BRACKETS
-            and self.leaves[-4].type == token.NAME
-            and (
-                # regular `from foo import bar,`
-                self.leaves[-4].value == "import"
-                # `from foo import (bar as baz,)
-                or (
-                    len(self.leaves) > 6
-                    and self.leaves[-6].value == "import"
-                    and self.leaves[-3].value == "as"
-                )
-                # `from foo import bar as baz,`
-                or (
-                    len(self.leaves) > 5
-                    and self.leaves[-5].value == "import"
-                    and self.leaves[-3].value == "as"
-                )
-            )
-            and closing.type == token.RPAR
-        ):
-            return False
-
-        self.remove_trailing_comma()
-        return True
-
-    def append_comment(self, comment: Leaf) -> bool:
-        """Add an inline or standalone comment to the line."""
-        if (
-            comment.type == STANDALONE_COMMENT
-            and self.bracket_tracker.any_open_brackets()
-        ):
-            comment.prefix = ""
-            return False
-
-        if comment.type != token.COMMENT:
-            return False
-
-        if not self.leaves:
-            comment.type = STANDALONE_COMMENT
-            comment.prefix = ""
-            return False
-
-        last_leaf = self.leaves[-1]
-        if (
-            last_leaf.type == token.RPAR
-            and not last_leaf.value
-            and last_leaf.parent
-            and len(list(last_leaf.parent.leaves())) <= 3
-            and not is_type_comment(comment)
-        ):
-            # Comments on an optional parens wrapping a single leaf should belong to
-            # the wrapped node except if it's a type comment. Pinning the comment like
-            # this avoids unstable formatting caused by comment migration.
-            if len(self.leaves) < 2:
-                comment.type = STANDALONE_COMMENT
-                comment.prefix = ""
-                return False
-            last_leaf = self.leaves[-2]
-        self.comments.setdefault(id(last_leaf), []).append(comment)
-        return True
-
-    def comments_after(self, leaf: Leaf) -> List[Leaf]:
-        """Generate comments that should appear directly after `leaf`."""
-        return self.comments.get(id(leaf), [])
-
-    def remove_trailing_comma(self) -> None:
-        """Remove the trailing comma and moves the comments attached to it."""
-        trailing_comma = self.leaves.pop()
-        trailing_comma_comments = self.comments.pop(id(trailing_comma), [])
-        self.comments.setdefault(id(self.leaves[-1]), []).extend(
-            trailing_comma_comments
-        )
-
-    def is_complex_subscript(self, leaf: Leaf) -> bool:
-        """Return True iff `leaf` is part of a slice with non-trivial exprs."""
-        open_lsqb = self.bracket_tracker.get_open_lsqb()
-        if open_lsqb is None:
-            return False
-
-        subscript_start = open_lsqb.next_sibling
-
-        if isinstance(subscript_start, Node):
-            if subscript_start.type == syms.listmaker:
-                return False
-
-            if subscript_start.type == syms.subscriptlist:
-                subscript_start = child_towards(subscript_start, leaf)
-        return subscript_start is not None and any(
-            n.type in TEST_DESCENDANTS for n in subscript_start.pre_order()
-        )
-
-    def __str__(self) -> str:
-        """Render the line."""
-        if not self:
-            return "\n"
-
-        indent = "    " * self.depth
-        leaves = iter(self.leaves)
-        first = next(leaves)
-        res = f"{first.prefix}{indent}{first.value}"
-        for leaf in leaves:
-            res += str(leaf)
-        for comment in itertools.chain.from_iterable(self.comments.values()):
-            res += str(comment)
-        return res + "\n"
-
-    def __bool__(self) -> bool:
-        """Return True if the line has leaves or comments."""
-        return bool(self.leaves or self.comments)
-
-
-@dataclass
-class EmptyLineTracker:
-    """Provides a stateful method that returns the number of potential extra
-    empty lines needed before and after the currently processed line.
-
-    Note: this tracker works on lines that haven't been split yet.  It assumes
-    the prefix of the first leaf consists of optional newlines.  Those newlines
-    are consumed by `maybe_empty_lines()` and included in the computation.
-    """
-
-    is_pyi: bool = False
-    previous_line: Optional[Line] = None
-    previous_after: int = 0
-    previous_defs: List[int] = Factory(list)
-
-    def maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
-        """Return the number of extra empty lines before and after the `current_line`.
-
-        This is for separating `def`, `async def` and `class` with extra empty
-        lines (two on module-level).
-        """
-        before, after = self._maybe_empty_lines(current_line)
-        before = (
-            # Black should not insert empty lines at the beginning
-            # of the file
-            0
-            if self.previous_line is None
-            else before - self.previous_after
-        )
-        self.previous_after = after
-        self.previous_line = current_line
-        return before, after
-
-    def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
-        max_allowed = 1
-        if current_line.depth == 0:
-            max_allowed = 1 if self.is_pyi else 2
-        if current_line.leaves:
-            # Consume the first leaf's extra newlines.
-            first_leaf = current_line.leaves[0]
-            before = first_leaf.prefix.count("\n")
-            before = min(before, max_allowed)
-            first_leaf.prefix = ""
-        else:
-            before = 0
-        depth = current_line.depth
-        while self.previous_defs and self.previous_defs[-1] >= depth:
-            self.previous_defs.pop()
-            if self.is_pyi:
-                before = 0 if depth else 1
-            else:
-                before = 1 if depth else 2
-        if current_line.is_decorator or current_line.is_def or current_line.is_class:
-            return self._maybe_empty_lines_for_class_or_def(current_line, before)
-
-        if (
-            self.previous_line
-            and self.previous_line.is_import
-            and not current_line.is_import
-            and depth == self.previous_line.depth
-        ):
-            return (before or 1), 0
-
-        if (
-            self.previous_line
-            and self.previous_line.is_class
-            and current_line.is_triple_quoted_string
-        ):
-            return before, 1
-
-        return before, 0
-
-    def _maybe_empty_lines_for_class_or_def(
-        self, current_line: Line, before: int
-    ) -> Tuple[int, int]:
-        if not current_line.is_decorator:
-            self.previous_defs.append(current_line.depth)
-        if self.previous_line is None:
-            # Don't insert empty lines before the first line in the file.
-            return 0, 0
-
-        if self.previous_line.is_decorator:
-            return 0, 0
-
-        if self.previous_line.depth < current_line.depth and (
-            self.previous_line.is_class or self.previous_line.is_def
-        ):
-            return 0, 0
-
-        if (
-            self.previous_line.is_comment
-            and self.previous_line.depth == current_line.depth
-            and before == 0
-        ):
-            return 0, 0
-
-        if self.is_pyi:
-            if self.previous_line.depth > current_line.depth:
-                newlines = 1
-            elif current_line.is_class or self.previous_line.is_class:
-                if current_line.is_stub_class and self.previous_line.is_stub_class:
-                    # No blank line between classes with an empty body
-                    newlines = 0
-                else:
-                    newlines = 1
-            elif current_line.is_def and not self.previous_line.is_def:
-                # Blank line between a block of functions and a block of non-functions
-                newlines = 1
-            else:
-                newlines = 0
-        else:
-            newlines = 2
-        if current_line.depth and newlines:
-            newlines -= 1
-        return newlines, 0
-
-
-@dataclass
-class LineGenerator(Visitor[Line]):
-    """Generates reformatted Line objects.  Empty lines are not emitted.
-
-    Note: destroys the tree it's visiting by mutating prefixes of its leaves
-    in ways that will no longer stringify to valid Python code on the tree.
-    """
-
-    is_pyi: bool = False
-    normalize_strings: bool = True
-    current_line: Line = Factory(Line)
-    remove_u_prefix: bool = False
-
-    def line(self, indent: int = 0) -> Iterator[Line]:
-        """Generate a line.
-
-        If the line is empty, only emit if it makes sense.
-        If the line is too long, split it first and then generate.
-
-        If any lines were generated, set up a new current_line.
-        """
-        if not self.current_line:
-            self.current_line.depth += indent
-            return  # Line is empty, don't emit. Creating a new one unnecessary.
-
-        complete_line = self.current_line
-        self.current_line = Line(depth=complete_line.depth + indent)
-        yield complete_line
-
-    def visit_default(self, node: LN) -> Iterator[Line]:
-        """Default `visit_*()` implementation. Recurses to children of `node`."""
-        if isinstance(node, Leaf):
-            any_open_brackets = self.current_line.bracket_tracker.any_open_brackets()
-            for comment in generate_comments(node):
-                if any_open_brackets:
-                    # any comment within brackets is subject to splitting
-                    self.current_line.append(comment)
-                elif comment.type == token.COMMENT:
-                    # regular trailing comment
-                    self.current_line.append(comment)
-                    yield from self.line()
-
-                else:
-                    # regular standalone comment
-                    yield from self.line()
-
-                    self.current_line.append(comment)
-                    yield from self.line()
-
-            normalize_prefix(node, inside_brackets=any_open_brackets)
-            if self.normalize_strings and node.type == token.STRING:
-                normalize_string_prefix(node, remove_u_prefix=self.remove_u_prefix)
-                normalize_string_quotes(node)
-            if node.type == token.NUMBER:
-                normalize_numeric_literal(node)
-            if node.type not in WHITESPACE:
-                self.current_line.append(node)
-        yield from super().visit_default(node)
-
-    def visit_atom(self, node: Node) -> Iterator[Line]:
-        # Always make parentheses invisible around a single node, because it should
-        # not be needed (except in the case of yield, where removing the parentheses
-        # produces a SyntaxError).
-        if (
-            len(node.children) == 3
-            and isinstance(node.children[0], Leaf)
-            and node.children[0].type == token.LPAR
-            and isinstance(node.children[2], Leaf)
-            and node.children[2].type == token.RPAR
-            and isinstance(node.children[1], Leaf)
-            and not (
-                node.children[1].type == token.NAME
-                and node.children[1].value == "yield"
-            )
-        ):
-            node.children[0].value = ""
-            node.children[2].value = ""
-        yield from super().visit_default(node)
-
-    def visit_factor(self, node: Node) -> Iterator[Line]:
-        """Force parentheses between a unary op and a binary power:
-
-        -2 ** 8 -> -(2 ** 8)
-        """
-        child = node.children[1]
-        if child.type == syms.power and len(child.children) == 3:
-            lpar = Leaf(token.LPAR, "(")
-            rpar = Leaf(token.RPAR, ")")
-            index = child.remove() or 0
-            node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
-        yield from self.visit_default(node)
-
-    def visit_INDENT(self, node: Node) -> Iterator[Line]:
-        """Increase indentation level, maybe yield a line."""
-        # In blib2to3 INDENT never holds comments.
-        yield from self.line(+1)
-        yield from self.visit_default(node)
-
-    def visit_DEDENT(self, node: Node) -> Iterator[Line]:
-        """Decrease indentation level, maybe yield a line."""
-        # The current line might still wait for trailing comments.  At DEDENT time
-        # there won't be any (they would be prefixes on the preceding NEWLINE).
-        # Emit the line then.
-        yield from self.line()
-
-        # While DEDENT has no value, its prefix may contain standalone comments
-        # that belong to the current indentation level.  Get 'em.
-        yield from self.visit_default(node)
-
-        # Finally, emit the dedent.
-        yield from self.line(-1)
-
-    def visit_stmt(
-        self, node: Node, keywords: Set[str], parens: Set[str]
-    ) -> Iterator[Line]:
-        """Visit a statement.
-
-        This implementation is shared for `if`, `while`, `for`, `try`, `except`,
-        `def`, `with`, `class`, `assert` and assignments.
-
-        The relevant Python language `keywords` for a given statement will be
-        NAME leaves within it. This methods puts those on a separate line.
-
-        `parens` holds a set of string leaf values immediately after which
-        invisible parens should be put.
-        """
-        normalize_invisible_parens(node, parens_after=parens)
-        for child in node.children:
-            if child.type == token.NAME and child.value in keywords:  # type: ignore
-                yield from self.line()
-
-            yield from self.visit(child)
-
-    def visit_suite(self, node: Node) -> Iterator[Line]:
-        """Visit a suite."""
-        if self.is_pyi and is_stub_suite(node):
-            yield from self.visit(node.children[2])
-        else:
-            yield from self.visit_default(node)
-
-    def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
-        """Visit a statement without nested statements."""
-        is_suite_like = node.parent and node.parent.type in STATEMENT
-        if is_suite_like:
-            if self.is_pyi and is_stub_body(node):
-                yield from self.visit_default(node)
-            else:
-                yield from self.line(+1)
-                yield from self.visit_default(node)
-                yield from self.line(-1)
-
-        else:
-            if not self.is_pyi or not node.parent or not is_stub_suite(node.parent):
-                yield from self.line()
-            yield from self.visit_default(node)
-
-    def visit_async_stmt(self, node: Node) -> Iterator[Line]:
-        """Visit `async def`, `async for`, `async with`."""
-        yield from self.line()
-
-        children = iter(node.children)
-        for child in children:
-            yield from self.visit(child)
-
-            if child.type == token.ASYNC:
-                break
-
-        internal_stmt = next(children)
-        for child in internal_stmt.children:
-            yield from self.visit(child)
-
-    def visit_decorators(self, node: Node) -> Iterator[Line]:
-        """Visit decorators."""
-        for child in node.children:
-            yield from self.line()
-            yield from self.visit(child)
-
-    def visit_SEMI(self, leaf: Leaf) -> Iterator[Line]:
-        """Remove a semicolon and put the other statement on a separate line."""
-        yield from self.line()
-
-    def visit_ENDMARKER(self, leaf: Leaf) -> Iterator[Line]:
-        """End of file. Process outstanding comments and end with a newline."""
-        yield from self.visit_default(leaf)
-        yield from self.line()
-
-    def visit_STANDALONE_COMMENT(self, leaf: Leaf) -> Iterator[Line]:
-        if not self.current_line.bracket_tracker.any_open_brackets():
-            yield from self.line()
-        yield from self.visit_default(leaf)
-
-    def __attrs_post_init__(self) -> None:
-        """You are in a twisty little maze of passages."""
-        v = self.visit_stmt
-        Ø: Set[str] = set()
-        self.visit_assert_stmt = partial(v, keywords={"assert"}, parens={"assert", ","})
-        self.visit_if_stmt = partial(
-            v, keywords={"if", "else", "elif"}, parens={"if", "elif"}
-        )
-        self.visit_while_stmt = partial(v, keywords={"while", "else"}, parens={"while"})
-        self.visit_for_stmt = partial(v, keywords={"for", "else"}, parens={"for", "in"})
-        self.visit_try_stmt = partial(
-            v, keywords={"try", "except", "else", "finally"}, parens=Ø
-        )
-        self.visit_except_clause = partial(v, keywords={"except"}, parens=Ø)
-        self.visit_with_stmt = partial(v, keywords={"with"}, parens=Ø)
-        self.visit_funcdef = partial(v, keywords={"def"}, parens=Ø)
-        self.visit_classdef = partial(v, keywords={"class"}, parens=Ø)
-        self.visit_expr_stmt = partial(v, keywords=Ø, parens=ASSIGNMENTS)
-        self.visit_return_stmt = partial(v, keywords={"return"}, parens={"return"})
-        self.visit_import_from = partial(v, keywords=Ø, parens={"import"})
-        self.visit_del_stmt = partial(v, keywords=Ø, parens={"del"})
-        self.visit_async_funcdef = self.visit_async_stmt
-        self.visit_decorated = self.visit_decorators
-
-
-IMPLICIT_TUPLE = {syms.testlist, syms.testlist_star_expr, syms.exprlist}
-BRACKET = {token.LPAR: token.RPAR, token.LSQB: token.RSQB, token.LBRACE: token.RBRACE}
-OPENING_BRACKETS = set(BRACKET.keys())
-CLOSING_BRACKETS = set(BRACKET.values())
-BRACKETS = OPENING_BRACKETS | CLOSING_BRACKETS
-ALWAYS_NO_SPACE = CLOSING_BRACKETS | {token.COMMA, STANDALONE_COMMENT}
-
-
-def whitespace(leaf: Leaf, *, complex_subscript: bool) -> str:  # noqa: C901
-    """Return whitespace prefix if needed for the given `leaf`.
-
-    `complex_subscript` signals whether the given leaf is part of a subscription
-    which has non-trivial arguments, like arithmetic expressions or function calls.
-    """
-    NO = ""
-    SPACE = " "
-    DOUBLESPACE = "  "
-    t = leaf.type
-    p = leaf.parent
-    v = leaf.value
-    if t in ALWAYS_NO_SPACE:
-        return NO
-
-    if t == token.COMMENT:
-        return DOUBLESPACE
-
-    assert p is not None, f"INTERNAL ERROR: hand-made leaf without parent: {leaf!r}"
-    if t == token.COLON and p.type not in {
-        syms.subscript,
-        syms.subscriptlist,
-        syms.sliceop,
-    }:
-        return NO
-
-    prev = leaf.prev_sibling
-    if not prev:
-        prevp = preceding_leaf(p)
-        if not prevp or prevp.type in OPENING_BRACKETS:
-            return NO
-
-        if t == token.COLON:
-            if prevp.type == token.COLON:
-                return NO
-
-            elif prevp.type != token.COMMA and not complex_subscript:
-                return NO
-
-            return SPACE
-
-        if prevp.type == token.EQUAL:
-            if prevp.parent:
-                if prevp.parent.type in {
-                    syms.arglist,
-                    syms.argument,
-                    syms.parameters,
-                    syms.varargslist,
-                }:
-                    return NO
-
-                elif prevp.parent.type == syms.typedargslist:
-                    # A bit hacky: if the equal sign has whitespace, it means we
-                    # previously found it's a typed argument.  So, we're using
-                    # that, too.
-                    return prevp.prefix
-
-        elif prevp.type in VARARGS_SPECIALS:
-            if is_vararg(prevp, within=VARARGS_PARENTS | UNPACKING_PARENTS):
-                return NO
-
-        elif prevp.type == token.COLON:
-            if prevp.parent and prevp.parent.type in {syms.subscript, syms.sliceop}:
-                return SPACE if complex_subscript else NO
-
-        elif (
-            prevp.parent
-            and prevp.parent.type == syms.factor
-            and prevp.type in MATH_OPERATORS
-        ):
-            return NO
-
-        elif (
-            prevp.type == token.RIGHTSHIFT
-            and prevp.parent
-            and prevp.parent.type == syms.shift_expr
-            and prevp.prev_sibling
-            and prevp.prev_sibling.type == token.NAME
-            and prevp.prev_sibling.value == "print"  # type: ignore
-        ):
-            # Python 2 print chevron
-            return NO
-
-    elif prev.type in OPENING_BRACKETS:
-        return NO
-
-    if p.type in {syms.parameters, syms.arglist}:
-        # untyped function signatures or calls
-        if not prev or prev.type != token.COMMA:
-            return NO
-
-    elif p.type == syms.varargslist:
-        # lambdas
-        if prev and prev.type != token.COMMA:
-            return NO
-
-    elif p.type == syms.typedargslist:
-        # typed function signatures
-        if not prev:
-            return NO
-
-        if t == token.EQUAL:
-            if prev.type != syms.tname:
-                return NO
-
-        elif prev.type == token.EQUAL:
-            # A bit hacky: if the equal sign has whitespace, it means we
-            # previously found it's a typed argument.  So, we're using that, too.
-            return prev.prefix
-
-        elif prev.type != token.COMMA:
-            return NO
-
-    elif p.type == syms.tname:
-        # type names
-        if not prev:
-            prevp = preceding_leaf(p)
-            if not prevp or prevp.type != token.COMMA:
-                return NO
-
-    elif p.type == syms.trailer:
-        # attributes and calls
-        if t == token.LPAR or t == token.RPAR:
-            return NO
-
-        if not prev:
-            if t == token.DOT:
-                prevp = preceding_leaf(p)
-                if not prevp or prevp.type != token.NUMBER:
-                    return NO
-
-            elif t == token.LSQB:
-                return NO
-
-        elif prev.type != token.COMMA:
-            return NO
-
-    elif p.type == syms.argument:
-        # single argument
-        if t == token.EQUAL:
-            return NO
-
-        if not prev:
-            prevp = preceding_leaf(p)
-            if not prevp or prevp.type == token.LPAR:
-                return NO
-
-        elif prev.type in {token.EQUAL} | VARARGS_SPECIALS:
-            return NO
-
-    elif p.type == syms.decorator:
-        # decorators
-        return NO
-
-    elif p.type == syms.dotted_name:
-        if prev:
-            return NO
-
-        prevp = preceding_leaf(p)
-        if not prevp or prevp.type == token.AT or prevp.type == token.DOT:
-            return NO
-
-    elif p.type == syms.classdef:
-        if t == token.LPAR:
-            return NO
-
-        if prev and prev.type == token.LPAR:
-            return NO
-
-    elif p.type in {syms.subscript, syms.sliceop}:
-        # indexing
-        if not prev:
-            assert p.parent is not None, "subscripts are always parented"
-            if p.parent.type == syms.subscriptlist:
-                return SPACE
-
-            return NO
-
-        elif not complex_subscript:
-            return NO
-
-    elif p.type == syms.atom:
-        if prev and t == token.DOT:
-            # dots, but not the first one.
-            return NO
-
-    elif p.type == syms.dictsetmaker:
-        # dict unpacking
-        if prev and prev.type == token.DOUBLESTAR:
-            return NO
-
-    elif p.type in {syms.factor, syms.star_expr}:
-        # unary ops
-        if not prev:
-            prevp = preceding_leaf(p)
-            if not prevp or prevp.type in OPENING_BRACKETS:
-                return NO
-
-            prevp_parent = prevp.parent
-            assert prevp_parent is not None
-            if prevp.type == token.COLON and prevp_parent.type in {
-                syms.subscript,
-                syms.sliceop,
-            }:
-                return NO
-
-            elif prevp.type == token.EQUAL and prevp_parent.type == syms.argument:
-                return NO
-
-        elif t in {token.NAME, token.NUMBER, token.STRING}:
-            return NO
-
-    elif p.type == syms.import_from:
-        if t == token.DOT:
-            if prev and prev.type == token.DOT:
-                return NO
-
-        elif t == token.NAME:
-            if v == "import":
-                return SPACE
-
-            if prev and prev.type == token.DOT:
-                return NO
-
-    elif p.type == syms.sliceop:
-        return NO
-
-    return SPACE
-
-
-def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]:
-    """Return the first leaf that precedes `node`, if any."""
-    while node:
-        res = node.prev_sibling
-        if res:
-            if isinstance(res, Leaf):
-                return res
-
-            try:
-                return list(res.leaves())[-1]
-
-            except IndexError:
-                return None
-
-        node = node.parent
-    return None
-
-
-def child_towards(ancestor: Node, descendant: LN) -> Optional[LN]:
-    """Return the child of `ancestor` that contains `descendant`."""
-    node: Optional[LN] = descendant
-    while node and node.parent != ancestor:
-        node = node.parent
-    return node
-
-
-def container_of(leaf: Leaf) -> LN:
-    """Return `leaf` or one of its ancestors that is the topmost container of it.
-
-    By "container" we mean a node where `leaf` is the very first child.
-    """
-    same_prefix = leaf.prefix
-    container: LN = leaf
-    while container:
-        parent = container.parent
-        if parent is None:
-            break
-
-        if parent.children[0].prefix != same_prefix:
-            break
-
-        if parent.type == syms.file_input:
-            break
-
-        if parent.prev_sibling is not None and parent.prev_sibling.type in BRACKETS:
-            break
-
-        container = parent
-    return container
-
-
-def is_split_after_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
-    """Return the priority of the `leaf` delimiter, given a line break after it.
-
-    The delimiter priorities returned here are from those delimiters that would
-    cause a line break after themselves.
-
-    Higher numbers are higher priority.
-    """
-    if leaf.type == token.COMMA:
-        return COMMA_PRIORITY
-
-    return 0
-
-
-def is_split_before_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
-    """Return the priority of the `leaf` delimiter, given a line break before it.
-
-    The delimiter priorities returned here are from those delimiters that would
-    cause a line break before themselves.
-
-    Higher numbers are higher priority.
-    """
-    if is_vararg(leaf, within=VARARGS_PARENTS | UNPACKING_PARENTS):
-        # * and ** might also be MATH_OPERATORS but in this case they are not.
-        # Don't treat them as a delimiter.
-        return 0
-
-    if (
-        leaf.type == token.DOT
-        and leaf.parent
-        and leaf.parent.type not in {syms.import_from, syms.dotted_name}
-        and (previous is None or previous.type in CLOSING_BRACKETS)
-    ):
-        return DOT_PRIORITY
-
-    if (
-        leaf.type in MATH_OPERATORS
-        and leaf.parent
-        and leaf.parent.type not in {syms.factor, syms.star_expr}
-    ):
-        return MATH_PRIORITIES[leaf.type]
-
-    if leaf.type in COMPARATORS:
-        return COMPARATOR_PRIORITY
-
-    if (
-        leaf.type == token.STRING
-        and previous is not None
-        and previous.type == token.STRING
-    ):
-        return STRING_PRIORITY
-
-    if leaf.type not in {token.NAME, token.ASYNC}:
-        return 0
-
-    if (
-        leaf.value == "for"
-        and leaf.parent
-        and leaf.parent.type in {syms.comp_for, syms.old_comp_for}
-        or leaf.type == token.ASYNC
-    ):
-        if (
-            not isinstance(leaf.prev_sibling, Leaf)
-            or leaf.prev_sibling.value != "async"
-        ):
-            return COMPREHENSION_PRIORITY
-
-    if (
-        leaf.value == "if"
-        and leaf.parent
-        and leaf.parent.type in {syms.comp_if, syms.old_comp_if}
-    ):
-        return COMPREHENSION_PRIORITY
-
-    if leaf.value in {"if", "else"} and leaf.parent and leaf.parent.type == syms.test:
-        return TERNARY_PRIORITY
-
-    if leaf.value == "is":
-        return COMPARATOR_PRIORITY
-
-    if (
-        leaf.value == "in"
-        and leaf.parent
-        and leaf.parent.type in {syms.comp_op, syms.comparison}
-        and not (
-            previous is not None
-            and previous.type == token.NAME
-            and previous.value == "not"
-        )
-    ):
-        return COMPARATOR_PRIORITY
-
-    if (
-        leaf.value == "not"
-        and leaf.parent
-        and leaf.parent.type == syms.comp_op
-        and not (
-            previous is not None
-            and previous.type == token.NAME
-            and previous.value == "is"
-        )
-    ):
-        return COMPARATOR_PRIORITY
-
-    if leaf.value in LOGIC_OPERATORS and leaf.parent:
-        return LOGIC_PRIORITY
-
-    return 0
-
-
-FMT_OFF = {"# fmt: off", "# fmt:off", "# yapf: disable"}
-FMT_ON = {"# fmt: on", "# fmt:on", "# yapf: enable"}
-
-
-def generate_comments(leaf: LN) -> Iterator[Leaf]:
-    """Clean the prefix of the `leaf` and generate comments from it, if any.
-
-    Comments in lib2to3 are shoved into the whitespace prefix.  This happens
-    in `pgen2/driver.py:Driver.parse_tokens()`.  This was a brilliant implementation
-    move because it does away with modifying the grammar to include all the
-    possible places in which comments can be placed.
-
-    The sad consequence for us though is that comments don't "belong" anywhere.
-    This is why this function generates simple parentless Leaf objects for
-    comments.  We simply don't know what the correct parent should be.
-
-    No matter though, we can live without this.  We really only need to
-    differentiate between inline and standalone comments.  The latter don't
-    share the line with any code.
-
-    Inline comments are emitted as regular token.COMMENT leaves.  Standalone
-    are emitted with a fake STANDALONE_COMMENT token identifier.
-    """
-    for pc in list_comments(leaf.prefix, is_endmarker=leaf.type == token.ENDMARKER):
-        yield Leaf(pc.type, pc.value, prefix="\n" * pc.newlines)
-
-
-@dataclass
-class ProtoComment:
-    """Describes a piece of syntax that is a comment.
-
-    It's not a :class:`blib2to3.pytree.Leaf` so that:
-
-    * it can be cached (`Leaf` objects should not be reused more than once as
-      they store their lineno, column, prefix, and parent information);
-    * `newlines` and `consumed` fields are kept separate from the `value`. This
-      simplifies handling of special marker comments like ``# fmt: off/on``.
-    """
-
-    type: int  # token.COMMENT or STANDALONE_COMMENT
-    value: str  # content of the comment
-    newlines: int  # how many newlines before the comment
-    consumed: int  # how many characters of the original leaf's prefix did we consume
-
-
-@lru_cache(maxsize=4096)
-def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
-    """Return a list of :class:`ProtoComment` objects parsed from the given `prefix`."""
-    result: List[ProtoComment] = []
-    if not prefix or "#" not in prefix:
-        return result
-
-    consumed = 0
-    nlines = 0
-    ignored_lines = 0
-    for index, line in enumerate(prefix.split("\n")):
-        consumed += len(line) + 1  # adding the length of the split '\n'
-        line = line.lstrip()
-        if not line:
-            nlines += 1
-        if not line.startswith("#"):
-            # Escaped newlines outside of a comment are not really newlines at
-            # all. We treat a single-line comment following an escaped newline
-            # as a simple trailing comment.
-            if line.endswith("\\"):
-                ignored_lines += 1
-            continue
-
-        if index == ignored_lines and not is_endmarker:
-            comment_type = token.COMMENT  # simple trailing comment
-        else:
-            comment_type = STANDALONE_COMMENT
-        comment = make_comment(line)
-        result.append(
-            ProtoComment(
-                type=comment_type, value=comment, newlines=nlines, consumed=consumed
-            )
-        )
-        nlines = 0
-    return result
-
-
-def make_comment(content: str) -> str:
-    """Return a consistently formatted comment from the given `content` string.
-
-    All comments (except for "##", "#!", "#:", '#'", "#%%") should have a single
-    space between the hash sign and the content.
-
-    If `content` didn't start with a hash sign, one is provided.
-    """
-    content = content.rstrip()
-    if not content:
-        return "#"
-
-    if content[0] == "#":
-        content = content[1:]
-    if content and content[0] not in " !:#'%":
-        content = " " + content
-    return "#" + content
-
-
-def split_line(
-    line: Line,
-    line_length: int,
-    inner: bool = False,
-    features: Collection[Feature] = (),
-) -> Iterator[Line]:
-    """Split a `line` into potentially many lines.
-
-    They should fit in the allotted `line_length` but might not be able to.
-    `inner` signifies that there were a pair of brackets somewhere around the
-    current `line`, possibly transitively. This means we can fallback to splitting
-    by delimiters if the LHS/RHS don't yield any results.
-
-    `features` are syntactical features that may be used in the output.
-    """
-    if line.is_comment:
-        yield line
-        return
-
-    line_str = str(line).strip("\n")
-
-    if (
-        not line.contains_uncollapsable_type_comments()
-        and not line.should_explode
-        and not line.is_collection_with_optional_trailing_comma
-        and (
-            is_line_short_enough(line, line_length=line_length, line_str=line_str)
-            or line.contains_unsplittable_type_ignore()
-        )
-    ):
-        yield line
-        return
-
-    split_funcs: List[SplitFunc]
-    if line.is_def:
-        split_funcs = [left_hand_split]
-    else:
-
-        def rhs(line: Line, features: Collection[Feature]) -> Iterator[Line]:
-            for omit in generate_trailers_to_omit(line, line_length):
-                lines = list(right_hand_split(line, line_length, features, omit=omit))
-                if is_line_short_enough(lines[0], line_length=line_length):
-                    yield from lines
-                    return
-
-            # All splits failed, best effort split with no omits.
-            # This mostly happens to multiline strings that are by definition
-            # reported as not fitting a single line.
-            yield from right_hand_split(line, line_length, features=features)
-
-        if line.inside_brackets:
-            split_funcs = [delimiter_split, standalone_comment_split, rhs]
-        else:
-            split_funcs = [rhs]
-    for split_func in split_funcs:
-        # We are accumulating lines in `result` because we might want to abort
-        # mission and return the original line in the end, or attempt a different
-        # split altogether.
-        result: List[Line] = []
-        try:
-            for l in split_func(line, features):
-                if str(l).strip("\n") == line_str:
-                    raise CannotSplit("Split function returned an unchanged result")
-
-                result.extend(
-                    split_line(
-                        l, line_length=line_length, inner=True, features=features
-                    )
-                )
-        except CannotSplit:
-            continue
-
-        else:
-            yield from result
-            break
-
-    else:
-        yield line
-
-
-def left_hand_split(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
-    """Split line into many lines, starting with the first matching bracket pair.
-
-    Note: this usually looks weird, only use this for function definitions.
-    Prefer RHS otherwise.  This is why this function is not symmetrical with
-    :func:`right_hand_split` which also handles optional parentheses.
-    """
-    tail_leaves: List[Leaf] = []
-    body_leaves: List[Leaf] = []
-    head_leaves: List[Leaf] = []
-    current_leaves = head_leaves
-    matching_bracket = None
-    for leaf in line.leaves:
-        if (
-            current_leaves is body_leaves
-            and leaf.type in CLOSING_BRACKETS
-            and leaf.opening_bracket is matching_bracket
-        ):
-            current_leaves = tail_leaves if body_leaves else head_leaves
-        current_leaves.append(leaf)
-        if current_leaves is head_leaves:
-            if leaf.type in OPENING_BRACKETS:
-                matching_bracket = leaf
-                current_leaves = body_leaves
-    if not matching_bracket:
-        raise CannotSplit("No brackets found")
-
-    head = bracket_split_build_line(head_leaves, line, matching_bracket)
-    body = bracket_split_build_line(body_leaves, line, matching_bracket, is_body=True)
-    tail = bracket_split_build_line(tail_leaves, line, matching_bracket)
-    bracket_split_succeeded_or_raise(head, body, tail)
-    for result in (head, body, tail):
-        if result:
-            yield result
-
-
-def right_hand_split(
-    line: Line,
-    line_length: int,
-    features: Collection[Feature] = (),
-    omit: Collection[LeafID] = (),
-) -> Iterator[Line]:
-    """Split line into many lines, starting with the last matching bracket pair.
-
-    If the split was by optional parentheses, attempt splitting without them, too.
-    `omit` is a collection of closing bracket IDs that shouldn't be considered for
-    this split.
-
-    Note: running this function modifies `bracket_depth` on the leaves of `line`.
-    """
-    tail_leaves: List[Leaf] = []
-    body_leaves: List[Leaf] = []
-    head_leaves: List[Leaf] = []
-    current_leaves = tail_leaves
-    opening_bracket = None
-    closing_bracket = None
-    for leaf in reversed(line.leaves):
-        if current_leaves is body_leaves:
-            if leaf is opening_bracket:
-                current_leaves = head_leaves if body_leaves else tail_leaves
-        current_leaves.append(leaf)
-        if current_leaves is tail_leaves:
-            if leaf.type in CLOSING_BRACKETS and id(leaf) not in omit:
-                opening_bracket = leaf.opening_bracket
-                closing_bracket = leaf
-                current_leaves = body_leaves
-    if not (opening_bracket and closing_bracket and head_leaves):
-        # If there is no opening or closing_bracket that means the split failed and
-        # all content is in the tail.  Otherwise, if `head_leaves` are empty, it means
-        # the matching `opening_bracket` wasn't available on `line` anymore.
-        raise CannotSplit("No brackets found")
-
-    tail_leaves.reverse()
-    body_leaves.reverse()
-    head_leaves.reverse()
-    head = bracket_split_build_line(head_leaves, line, opening_bracket)
-    body = bracket_split_build_line(body_leaves, line, opening_bracket, is_body=True)
-    tail = bracket_split_build_line(tail_leaves, line, opening_bracket)
-    bracket_split_succeeded_or_raise(head, body, tail)
-    if (
-        # the body shouldn't be exploded
-        not body.should_explode
-        # the opening bracket is an optional paren
-        and opening_bracket.type == token.LPAR
-        and not opening_bracket.value
-        # the closing bracket is an optional paren
-        and closing_bracket.type == token.RPAR
-        and not closing_bracket.value
-        # it's not an import (optional parens are the only thing we can split on
-        # in this case; attempting a split without them is a waste of time)
-        and not line.is_import
-        # there are no standalone comments in the body
-        and not body.contains_standalone_comments(0)
-        # and we can actually remove the parens
-        and can_omit_invisible_parens(body, line_length)
-    ):
-        omit = {id(closing_bracket), *omit}
-        try:
-            yield from right_hand_split(line, line_length, features=features, omit=omit)
-            return
-
-        except CannotSplit:
-            if not (
-                can_be_split(body)
-                or is_line_short_enough(body, line_length=line_length)
-            ):
-                raise CannotSplit(
-                    "Splitting failed, body is still too long and can't be split."
-                )
-
-            elif head.contains_multiline_strings() or tail.contains_multiline_strings():
-                raise CannotSplit(
-                    "The current optional pair of parentheses is bound to fail to "
-                    "satisfy the splitting algorithm because the head or the tail "
-                    "contains multiline strings which by definition never fit one "
-                    "line."
-                )
-
-    ensure_visible(opening_bracket)
-    ensure_visible(closing_bracket)
-    for result in (head, body, tail):
-        if result:
-            yield result
-
-
-def bracket_split_succeeded_or_raise(head: Line, body: Line, tail: Line) -> None:
-    """Raise :exc:`CannotSplit` if the last left- or right-hand split failed.
-
-    Do nothing otherwise.
-
-    A left- or right-hand split is based on a pair of brackets. Content before
-    (and including) the opening bracket is left on one line, content inside the
-    brackets is put on a separate line, and finally content starting with and
-    following the closing bracket is put on a separate line.
-
-    Those are called `head`, `body`, and `tail`, respectively. If the split
-    produced the same line (all content in `head`) or ended up with an empty `body`
-    and the `tail` is just the closing bracket, then it's considered failed.
-    """
-    tail_len = len(str(tail).strip())
-    if not body:
-        if tail_len == 0:
-            raise CannotSplit("Splitting brackets produced the same line")
-
-        elif tail_len < 3:
-            raise CannotSplit(
-                f"Splitting brackets on an empty body to save "
-                f"{tail_len} characters is not worth it"
-            )
-
-
-def bracket_split_build_line(
-    leaves: List[Leaf], original: Line, opening_bracket: Leaf, *, is_body: bool = False
-) -> Line:
-    """Return a new line with given `leaves` and respective comments from `original`.
-
-    If `is_body` is True, the result line is one-indented inside brackets and as such
-    has its first leaf's prefix normalized and a trailing comma added when expected.
-    """
-    result = Line(depth=original.depth)
-    if is_body:
-        result.inside_brackets = True
-        result.depth += 1
-        if leaves:
-            # Since body is a new indent level, remove spurious leading whitespace.
-            normalize_prefix(leaves[0], inside_brackets=True)
-            # Ensure a trailing comma for imports and standalone function arguments, but
-            # be careful not to add one after any comments.
-            no_commas = original.is_def and not any(
-                l.type == token.COMMA for l in leaves
-            )
-
-            if original.is_import or no_commas:
-                for i in range(len(leaves) - 1, -1, -1):
-                    if leaves[i].type == STANDALONE_COMMENT:
-                        continue
-                    elif leaves[i].type == token.COMMA:
-                        break
-                    else:
-                        leaves.insert(i + 1, Leaf(token.COMMA, ","))
-                        break
-    # Populate the line
-    for leaf in leaves:
-        result.append(leaf, preformatted=True)
-        for comment_after in original.comments_after(leaf):
-            result.append(comment_after, preformatted=True)
-    if is_body:
-        result.should_explode = should_explode(result, opening_bracket)
-    return result
-
-
-def dont_increase_indentation(split_func: SplitFunc) -> SplitFunc:
-    """Normalize prefix of the first leaf in every line returned by `split_func`.
-
-    This is a decorator over relevant split functions.
-    """
-
-    @wraps(split_func)
-    def split_wrapper(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
-        for l in split_func(line, features):
-            normalize_prefix(l.leaves[0], inside_brackets=True)
-            yield l
-
-    return split_wrapper
-
-
-@dont_increase_indentation
-def delimiter_split(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
-    """Split according to delimiters of the highest priority.
-
-    If the appropriate Features are given, the split will add trailing commas
-    also in function signatures and calls that contain `*` and `**`.
-    """
-    try:
-        last_leaf = line.leaves[-1]
-    except IndexError:
-        raise CannotSplit("Line empty")
-
-    bt = line.bracket_tracker
-    try:
-        delimiter_priority = bt.max_delimiter_priority(exclude={id(last_leaf)})
-    except ValueError:
-        raise CannotSplit("No delimiters found")
-
-    if delimiter_priority == DOT_PRIORITY:
-        if bt.delimiter_count_with_priority(delimiter_priority) == 1:
-            raise CannotSplit("Splitting a single attribute from its owner looks wrong")
-
-    current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
-    lowest_depth = sys.maxsize
-    trailing_comma_safe = True
-
-    def append_to_line(leaf: Leaf) -> Iterator[Line]:
-        """Append `leaf` to current line or to new line if appending impossible."""
-        nonlocal current_line
-        try:
-            current_line.append_safe(leaf, preformatted=True)
-        except ValueError:
-            yield current_line
-
-            current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
-            current_line.append(leaf)
-
-    for leaf in line.leaves:
-        yield from append_to_line(leaf)
-
-        for comment_after in line.comments_after(leaf):
-            yield from append_to_line(comment_after)
-
-        lowest_depth = min(lowest_depth, leaf.bracket_depth)
-        if leaf.bracket_depth == lowest_depth:
-            if is_vararg(leaf, within={syms.typedargslist}):
-                trailing_comma_safe = (
-                    trailing_comma_safe and Feature.TRAILING_COMMA_IN_DEF in features
-                )
-            elif is_vararg(leaf, within={syms.arglist, syms.argument}):
-                trailing_comma_safe = (
-                    trailing_comma_safe and Feature.TRAILING_COMMA_IN_CALL in features
-                )
-
-        leaf_priority = bt.delimiters.get(id(leaf))
-        if leaf_priority == delimiter_priority:
-            yield current_line
-
-            current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
-    if current_line:
-        if (
-            trailing_comma_safe
-            and delimiter_priority == COMMA_PRIORITY
-            and current_line.leaves[-1].type != token.COMMA
-            and current_line.leaves[-1].type != STANDALONE_COMMENT
-        ):
-            current_line.append(Leaf(token.COMMA, ","))
-        yield current_line
-
-
-@dont_increase_indentation
-def standalone_comment_split(
-    line: Line, features: Collection[Feature] = ()
-) -> Iterator[Line]:
-    """Split standalone comments from the rest of the line."""
-    if not line.contains_standalone_comments(0):
-        raise CannotSplit("Line does not have any standalone comments")
-
-    current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
-
-    def append_to_line(leaf: Leaf) -> Iterator[Line]:
-        """Append `leaf` to current line or to new line if appending impossible."""
-        nonlocal current_line
-        try:
-            current_line.append_safe(leaf, preformatted=True)
-        except ValueError:
-            yield current_line
-
-            current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
-            current_line.append(leaf)
-
-    for leaf in line.leaves:
-        yield from append_to_line(leaf)
-
-        for comment_after in line.comments_after(leaf):
-            yield from append_to_line(comment_after)
-
-    if current_line:
-        yield current_line
-
-
-def is_import(leaf: Leaf) -> bool:
-    """Return True if the given leaf starts an import statement."""
-    p = leaf.parent
-    t = leaf.type
-    v = leaf.value
-    return bool(
-        t == token.NAME
-        and (
-            (v == "import" and p and p.type == syms.import_name)
-            or (v == "from" and p and p.type == syms.import_from)
-        )
-    )
-
-
-def is_type_comment(leaf: Leaf, suffix: str = "") -> bool:
-    """Return True if the given leaf is a special comment.
-    Only returns true for type comments for now."""
-    t = leaf.type
-    v = leaf.value
-    return t in {token.COMMENT, t == STANDALONE_COMMENT} and v.startswith(
-        "# type:" + suffix
-    )
-
-
-def normalize_prefix(leaf: Leaf, *, inside_brackets: bool) -> None:
-    """Leave existing extra newlines if not `inside_brackets`. Remove everything
-    else.
-
-    Note: don't use backslashes for formatting or you'll lose your voting rights.
-    """
-    if not inside_brackets:
-        spl = leaf.prefix.split("#")
-        if "\\" not in spl[0]:
-            nl_count = spl[-1].count("\n")
-            if len(spl) > 1:
-                nl_count -= 1
-            leaf.prefix = "\n" * nl_count
-            return
-
-    leaf.prefix = ""
-
-
-def normalize_string_prefix(leaf: Leaf, remove_u_prefix: bool = False) -> None:
-    """Make all string prefixes lowercase.
-
-    If remove_u_prefix is given, also removes any u prefix from the string.
-
-    Note: Mutates its argument.
-    """
-    match = re.match(r"^([furbFURB]*)(.*)$", leaf.value, re.DOTALL)
-    assert match is not None, f"failed to match string {leaf.value!r}"
-    orig_prefix = match.group(1)
-    new_prefix = orig_prefix.lower()
-    if remove_u_prefix:
-        new_prefix = new_prefix.replace("u", "")
-    leaf.value = f"{new_prefix}{match.group(2)}"
-
-
-def normalize_string_quotes(leaf: Leaf) -> None:
-    """Prefer double quotes but only if it doesn't cause more escaping.
-
-    Adds or removes backslashes as appropriate. Doesn't parse and fix
-    strings nested in f-strings (yet).
-
-    Note: Mutates its argument.
-    """
-    value = leaf.value.lstrip("furbFURB")
-    if value[:3] == '"""':
-        return
-
-    elif value[:3] == "'''":
-        orig_quote = "'''"
-        new_quote = '"""'
-    elif value[0] == '"':
-        orig_quote = '"'
-        new_quote = "'"
-    else:
-        orig_quote = "'"
-        new_quote = '"'
-    first_quote_pos = leaf.value.find(orig_quote)
-    if first_quote_pos == -1:
-        return  # There's an internal error
-
-    prefix = leaf.value[:first_quote_pos]
-    unescaped_new_quote = re.compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
-    escaped_new_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){new_quote}")
-    escaped_orig_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){orig_quote}")
-    body = leaf.value[first_quote_pos + len(orig_quote) : -len(orig_quote)]
-    if "r" in prefix.casefold():
-        if unescaped_new_quote.search(body):
-            # There's at least one unescaped new_quote in this raw string
-            # so converting is impossible
-            return
-
-        # Do not introduce or remove backslashes in raw strings
-        new_body = body
-    else:
-        # remove unnecessary escapes
-        new_body = sub_twice(escaped_new_quote, rf"\1\2{new_quote}", body)
-        if body != new_body:
-            # Consider the string without unnecessary escapes as the original
-            body = new_body
-            leaf.value = f"{prefix}{orig_quote}{body}{orig_quote}"
-        new_body = sub_twice(escaped_orig_quote, rf"\1\2{orig_quote}", new_body)
-        new_body = sub_twice(unescaped_new_quote, rf"\1\\{new_quote}", new_body)
-    if "f" in prefix.casefold():
-        matches = re.findall(
-            r"""
-            (?:[^{]|^)\{  # start of the string or a non-{ followed by a single {
-                ([^{].*?)  # contents of the brackets except if begins with {{
-            \}(?:[^}]|$)  # A } followed by end of the string or a non-}
-            """,
-            new_body,
-            re.VERBOSE,
-        )
-        for m in matches:
-            if "\\" in str(m):
-                # Do not introduce backslashes in interpolated expressions
-                return
-    if new_quote == '"""' and new_body[-1:] == '"':
-        # edge case:
-        new_body = new_body[:-1] + '\\"'
-    orig_escape_count = body.count("\\")
-    new_escape_count = new_body.count("\\")
-    if new_escape_count > orig_escape_count:
-        return  # Do not introduce more escaping
-
-    if new_escape_count == orig_escape_count and orig_quote == '"':
-        return  # Prefer double quotes
-
-    leaf.value = f"{prefix}{new_quote}{new_body}{new_quote}"
-
-
-def normalize_numeric_literal(leaf: Leaf) -> None:
-    """Normalizes numeric (float, int, and complex) literals.
-
-    All letters used in the representation are normalized to lowercase (except
-    in Python 2 long literals).
-    """
-    text = leaf.value.lower()
-    if text.startswith(("0o", "0b")):
-        # Leave octal and binary literals alone.
-        pass
-    elif text.startswith("0x"):
-        # Change hex literals to upper case.
-        before, after = text[:2], text[2:]
-        text = f"{before}{after.upper()}"
-    elif "e" in text:
-        before, after = text.split("e")
-        sign = ""
-        if after.startswith("-"):
-            after = after[1:]
-            sign = "-"
-        elif after.startswith("+"):
-            after = after[1:]
-        before = format_float_or_int_string(before)
-        text = f"{before}e{sign}{after}"
-    elif text.endswith(("j", "l")):
-        number = text[:-1]
-        suffix = text[-1]
-        # Capitalize in "2L" because "l" looks too similar to "1".
-        if suffix == "l":
-            suffix = "L"
-        text = f"{format_float_or_int_string(number)}{suffix}"
-    else:
-        text = format_float_or_int_string(text)
-    leaf.value = text
-
-
-def format_float_or_int_string(text: str) -> str:
-    """Formats a float string like "1.0"."""
-    if "." not in text:
-        return text
-
-    before, after = text.split(".")
-    return f"{before or 0}.{after or 0}"
-
-
-def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
-    """Make existing optional parentheses invisible or create new ones.
-
-    `parens_after` is a set of string leaf values immediately after which parens
-    should be put.
-
-    Standardizes on visible parentheses for single-element tuples, and keeps
-    existing visible parentheses for other tuples and generator expressions.
-    """
-    for pc in list_comments(node.prefix, is_endmarker=False):
-        if pc.value in FMT_OFF:
-            # This `node` has a prefix with `# fmt: off`, don't mess with parens.
-            return
-
-    check_lpar = False
-    for index, child in enumerate(list(node.children)):
-        # Add parentheses around long tuple unpacking in assignments.
-        if (
-            index == 0
-            and isinstance(child, Node)
-            and child.type == syms.testlist_star_expr
-        ):
-            check_lpar = True
-
-        if check_lpar:
-            if is_walrus_assignment(child):
-                continue
-            if child.type == syms.atom:
-                # Determines if the underlying atom should be surrounded with
-                # invisible params - also makes parens invisible recursively
-                # within the atom and removes repeated invisible parens within
-                # the atom
-                should_surround_with_parens = maybe_make_parens_invisible_in_atom(
-                    child, parent=node
-                )
-
-                if should_surround_with_parens:
-                    lpar = Leaf(token.LPAR, "")
-                    rpar = Leaf(token.RPAR, "")
-                    index = child.remove() or 0
-                    node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
-            elif is_one_tuple(child):
-                # wrap child in visible parentheses
-                lpar = Leaf(token.LPAR, "(")
-                rpar = Leaf(token.RPAR, ")")
-                child.remove()
-                node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
-            elif node.type == syms.import_from:
-                # "import from" nodes store parentheses directly as part of
-                # the statement
-                if child.type == token.LPAR:
-                    # make parentheses invisible
-                    child.value = ""  # type: ignore
-                    node.children[-1].value = ""  # type: ignore
-                elif child.type != token.STAR:
-                    # insert invisible parentheses
-                    node.insert_child(index, Leaf(token.LPAR, ""))
-                    node.append_child(Leaf(token.RPAR, ""))
-                break
-
-            elif not (isinstance(child, Leaf) and is_multiline_string(child)):
-                # wrap child in invisible parentheses
-                lpar = Leaf(token.LPAR, "")
-                rpar = Leaf(token.RPAR, "")
-                index = child.remove() or 0
-                prefix = child.prefix
-                child.prefix = ""
-                new_child = Node(syms.atom, [lpar, child, rpar])
-                new_child.prefix = prefix
-                node.insert_child(index, new_child)
-
-        check_lpar = isinstance(child, Leaf) and child.value in parens_after
-
-
-def normalize_fmt_off(node: Node) -> None:
-    """Convert content between `# fmt: off`/`# fmt: on` into standalone comments."""
-    try_again = True
-    while try_again:
-        try_again = convert_one_fmt_off_pair(node)
-
-
-def convert_one_fmt_off_pair(node: Node) -> bool:
-    """Convert content of a single `# fmt: off`/`# fmt: on` into a standalone comment.
-
-    Returns True if a pair was converted.
-    """
-    for leaf in node.leaves():
-        previous_consumed = 0
-        for comment in list_comments(leaf.prefix, is_endmarker=False):
-            if comment.value in FMT_OFF:
-                # We only want standalone comments. If there's no previous leaf or
-                # the previous leaf is indentation, it's a standalone comment in
-                # disguise.
-                if comment.type != STANDALONE_COMMENT:
-                    prev = preceding_leaf(leaf)
-                    if prev and prev.type not in WHITESPACE:
-                        continue
-
-                ignored_nodes = list(generate_ignored_nodes(leaf))
-                if not ignored_nodes:
-                    continue
-
-                first = ignored_nodes[0]  # Can be a container node with the `leaf`.
-                parent = first.parent
-                prefix = first.prefix
-                first.prefix = prefix[comment.consumed :]
-                hidden_value = (
-                    comment.value + "\n" + "".join(str(n) for n in ignored_nodes)
-                )
-                if hidden_value.endswith("\n"):
-                    # That happens when one of the `ignored_nodes` ended with a NEWLINE
-                    # leaf (possibly followed by a DEDENT).
-                    hidden_value = hidden_value[:-1]
-                first_idx = None
-                for ignored in ignored_nodes:
-                    index = ignored.remove()
-                    if first_idx is None:
-                        first_idx = index
-                assert parent is not None, "INTERNAL ERROR: fmt: on/off handling (1)"
-                assert first_idx is not None, "INTERNAL ERROR: fmt: on/off handling (2)"
-                parent.insert_child(
-                    first_idx,
-                    Leaf(
-                        STANDALONE_COMMENT,
-                        hidden_value,
-                        prefix=prefix[:previous_consumed] + "\n" * comment.newlines,
-                    ),
-                )
-                return True
-
-            previous_consumed = comment.consumed
-
-    return False
-
-
-def generate_ignored_nodes(leaf: Leaf) -> Iterator[LN]:
-    """Starting from the container of `leaf`, generate all leaves until `# fmt: on`.
-
-    Stops at the end of the block.
-    """
-    container: Optional[LN] = container_of(leaf)
-    while container is not None and container.type != token.ENDMARKER:
-        for comment in list_comments(container.prefix, is_endmarker=False):
-            if comment.value in FMT_ON:
-                return
-
-        yield container
-
-        container = container.next_sibling
-
-
-def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
-    """If it's safe, make the parens in the atom `node` invisible, recursively.
-    Additionally, remove repeated, adjacent invisible parens from the atom `node`
-    as they are redundant.
-
-    Returns whether the node should itself be wrapped in invisible parentheses.
-
-    """
-    if (
-        node.type != syms.atom
-        or is_empty_tuple(node)
-        or is_one_tuple(node)
-        or (is_yield(node) and parent.type != syms.expr_stmt)
-        or max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
-    ):
-        return False
-
-    first = node.children[0]
-    last = node.children[-1]
-    if first.type == token.LPAR and last.type == token.RPAR:
-        middle = node.children[1]
-        # make parentheses invisible
-        first.value = ""  # type: ignore
-        last.value = ""  # type: ignore
-        maybe_make_parens_invisible_in_atom(middle, parent=parent)
-
-        if is_atom_with_invisible_parens(middle):
-            # Strip the invisible parens from `middle` by replacing
-            # it with the child in-between the invisible parens
-            middle.replace(middle.children[1])
-
-        return False
-
-    return True
-
-
-def is_atom_with_invisible_parens(node: LN) -> bool:
-    """Given a `LN`, determines whether it's an atom `node` with invisible
-    parens. Useful in dedupe-ing and normalizing parens.
-    """
-    if isinstance(node, Leaf) or node.type != syms.atom:
-        return False
-
-    first, last = node.children[0], node.children[-1]
-    return (
-        isinstance(first, Leaf)
-        and first.type == token.LPAR
-        and first.value == ""
-        and isinstance(last, Leaf)
-        and last.type == token.RPAR
-        and last.value == ""
-    )
-
-
-def is_empty_tuple(node: LN) -> bool:
-    """Return True if `node` holds an empty tuple."""
-    return (
-        node.type == syms.atom
-        and len(node.children) == 2
-        and node.children[0].type == token.LPAR
-        and node.children[1].type == token.RPAR
-    )
-
-
-def unwrap_singleton_parenthesis(node: LN) -> Optional[LN]:
-    """Returns `wrapped` if `node` is of the shape ( wrapped ).
-
-    Parenthesis can be optional. Returns None otherwise"""
-    if len(node.children) != 3:
-        return None
-    lpar, wrapped, rpar = node.children
-    if not (lpar.type == token.LPAR and rpar.type == token.RPAR):
-        return None
-
-    return wrapped
-
-
-def is_one_tuple(node: LN) -> bool:
-    """Return True if `node` holds a tuple with one element, with or without parens."""
-    if node.type == syms.atom:
-        gexp = unwrap_singleton_parenthesis(node)
-        if gexp is None or gexp.type != syms.testlist_gexp:
-            return False
-
-        return len(gexp.children) == 2 and gexp.children[1].type == token.COMMA
-
-    return (
-        node.type in IMPLICIT_TUPLE
-        and len(node.children) == 2
-        and node.children[1].type == token.COMMA
-    )
-
-
-def is_walrus_assignment(node: LN) -> bool:
-    """Return True iff `node` is of the shape ( test := test )"""
-    inner = unwrap_singleton_parenthesis(node)
-    return inner is not None and inner.type == syms.namedexpr_test
-
-
-def is_yield(node: LN) -> bool:
-    """Return True if `node` holds a `yield` or `yield from` expression."""
-    if node.type == syms.yield_expr:
-        return True
-
-    if node.type == token.NAME and node.value == "yield":  # type: ignore
-        return True
-
-    if node.type != syms.atom:
-        return False
-
-    if len(node.children) != 3:
-        return False
-
-    lpar, expr, rpar = node.children
-    if lpar.type == token.LPAR and rpar.type == token.RPAR:
-        return is_yield(expr)
-
-    return False
-
-
-def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
-    """Return True if `leaf` is a star or double star in a vararg or kwarg.
-
-    If `within` includes VARARGS_PARENTS, this applies to function signatures.
-    If `within` includes UNPACKING_PARENTS, it applies to right hand-side
-    extended iterable unpacking (PEP 3132) and additional unpacking
-    generalizations (PEP 448).
-    """
-    if leaf.type not in VARARGS_SPECIALS or not leaf.parent:
-        return False
-
-    p = leaf.parent
-    if p.type == syms.star_expr:
-        # Star expressions are also used as assignment targets in extended
-        # iterable unpacking (PEP 3132).  See what its parent is instead.
-        if not p.parent:
-            return False
-
-        p = p.parent
-
-    return p.type in within
-
-
-def is_multiline_string(leaf: Leaf) -> bool:
-    """Return True if `leaf` is a multiline string that actually spans many lines."""
-    value = leaf.value.lstrip("furbFURB")
-    return value[:3] in {'"""', "'''"} and "\n" in value
-
-
-def is_stub_suite(node: Node) -> bool:
-    """Return True if `node` is a suite with a stub body."""
-    if (
-        len(node.children) != 4
-        or node.children[0].type != token.NEWLINE
-        or node.children[1].type != token.INDENT
-        or node.children[3].type != token.DEDENT
-    ):
-        return False
-
-    return is_stub_body(node.children[2])
-
-
-def is_stub_body(node: LN) -> bool:
-    """Return True if `node` is a simple statement containing an ellipsis."""
-    if not isinstance(node, Node) or node.type != syms.simple_stmt:
-        return False
-
-    if len(node.children) != 2:
-        return False
-
-    child = node.children[0]
-    return (
-        child.type == syms.atom
-        and len(child.children) == 3
-        and all(leaf == Leaf(token.DOT, ".") for leaf in child.children)
-    )
-
-
-def max_delimiter_priority_in_atom(node: LN) -> Priority:
-    """Return maximum delimiter priority inside `node`.
-
-    This is specific to atoms with contents contained in a pair of parentheses.
-    If `node` isn't an atom or there are no enclosing parentheses, returns 0.
-    """
-    if node.type != syms.atom:
-        return 0
-
-    first = node.children[0]
-    last = node.children[-1]
-    if not (first.type == token.LPAR and last.type == token.RPAR):
-        return 0
-
-    bt = BracketTracker()
-    for c in node.children[1:-1]:
-        if isinstance(c, Leaf):
-            bt.mark(c)
-        else:
-            for leaf in c.leaves():
-                bt.mark(leaf)
-    try:
-        return bt.max_delimiter_priority()
-
-    except ValueError:
-        return 0
-
-
-def ensure_visible(leaf: Leaf) -> None:
-    """Make sure parentheses are visible.
-
-    They could be invisible as part of some statements (see
-    :func:`normalize_invisible_parens` and :func:`visit_import_from`).
-    """
-    if leaf.type == token.LPAR:
-        leaf.value = "("
-    elif leaf.type == token.RPAR:
-        leaf.value = ")"
-
-
-def should_explode(line: Line, opening_bracket: Leaf) -> bool:
-    """Should `line` immediately be split with `delimiter_split()` after RHS?"""
-
-    if not (
-        opening_bracket.parent
-        and opening_bracket.parent.type in {syms.atom, syms.import_from}
-        and opening_bracket.value in "[{("
-    ):
-        return False
-
-    try:
-        last_leaf = line.leaves[-1]
-        exclude = {id(last_leaf)} if last_leaf.type == token.COMMA else set()
-        max_priority = line.bracket_tracker.max_delimiter_priority(exclude=exclude)
-    except (IndexError, ValueError):
-        return False
-
-    return max_priority == COMMA_PRIORITY
-
-
-def get_features_used(node: Node) -> Set[Feature]:
-    """Return a set of (relatively) new Python features used in this file.
-
-    Currently looking for:
-    - f-strings;
-    - underscores in numeric literals;
-    - trailing commas after * or ** in function signatures and calls;
-    - positional only arguments in function signatures and lambdas;
-    """
-    features: Set[Feature] = set()
-    for n in node.pre_order():
-        if n.type == token.STRING:
-            value_head = n.value[:2]  # type: ignore
-            if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}:
-                features.add(Feature.F_STRINGS)
-
-        elif n.type == token.NUMBER:
-            if "_" in n.value:  # type: ignore
-                features.add(Feature.NUMERIC_UNDERSCORES)
-
-        elif n.type == token.SLASH:
-            if n.parent and n.parent.type in {syms.typedargslist, syms.arglist}:
-                features.add(Feature.POS_ONLY_ARGUMENTS)
-
-        elif n.type == token.COLONEQUAL:
-            features.add(Feature.ASSIGNMENT_EXPRESSIONS)
-
-        elif (
-            n.type in {syms.typedargslist, syms.arglist}
-            and n.children
-            and n.children[-1].type == token.COMMA
-        ):
-            if n.type == syms.typedargslist:
-                feature = Feature.TRAILING_COMMA_IN_DEF
-            else:
-                feature = Feature.TRAILING_COMMA_IN_CALL
-
-            for ch in n.children:
-                if ch.type in STARS:
-                    features.add(feature)
-
-                if ch.type == syms.argument:
-                    for argch in ch.children:
-                        if argch.type in STARS:
-                            features.add(feature)
-
-    return features
-
-
-def detect_target_versions(node: Node) -> Set[TargetVersion]:
-    """Detect the version to target based on the nodes used."""
-    features = get_features_used(node)
-    return {
-        version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
-    }
-
-
-def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[Set[LeafID]]:
-    """Generate sets of closing bracket IDs that should be omitted in a RHS.
-
-    Brackets can be omitted if the entire trailer up to and including
-    a preceding closing bracket fits in one line.
-
-    Yielded sets are cumulative (contain results of previous yields, too).  First
-    set is empty.
-    """
-
-    omit: Set[LeafID] = set()
-    yield omit
-
-    length = 4 * line.depth
-    opening_bracket = None
-    closing_bracket = None
-    inner_brackets: Set[LeafID] = set()
-    for index, leaf, leaf_length in enumerate_with_length(line, reversed=True):
-        length += leaf_length
-        if length > line_length:
-            break
-
-        has_inline_comment = leaf_length > len(leaf.value) + len(leaf.prefix)
-        if leaf.type == STANDALONE_COMMENT or has_inline_comment:
-            break
-
-        if opening_bracket:
-            if leaf is opening_bracket:
-                opening_bracket = None
-            elif leaf.type in CLOSING_BRACKETS:
-                inner_brackets.add(id(leaf))
-        elif leaf.type in CLOSING_BRACKETS:
-            if index > 0 and line.leaves[index - 1].type in OPENING_BRACKETS:
-                # Empty brackets would fail a split so treat them as "inner"
-                # brackets (e.g. only add them to the `omit` set if another
-                # pair of brackets was good enough.
-                inner_brackets.add(id(leaf))
-                continue
-
-            if closing_bracket:
-                omit.add(id(closing_bracket))
-                omit.update(inner_brackets)
-                inner_brackets.clear()
-                yield omit
-
-            if leaf.value:
-                opening_bracket = leaf.opening_bracket
-                closing_bracket = leaf
-
-
-def get_future_imports(node: Node) -> Set[str]:
-    """Return a set of __future__ imports in the file."""
-    imports: Set[str] = set()
-
-    def get_imports_from_children(children: List[LN]) -> Generator[str, None, None]:
-        for child in children:
-            if isinstance(child, Leaf):
-                if child.type == token.NAME:
-                    yield child.value
-            elif child.type == syms.import_as_name:
-                orig_name = child.children[0]
-                assert isinstance(orig_name, Leaf), "Invalid syntax parsing imports"
-                assert orig_name.type == token.NAME, "Invalid syntax parsing imports"
-                yield orig_name.value
-            elif child.type == syms.import_as_names:
-                yield from get_imports_from_children(child.children)
-            else:
-                raise AssertionError("Invalid syntax parsing imports")
-
-    for child in node.children:
-        if child.type != syms.simple_stmt:
-            break
-        first_child = child.children[0]
-        if isinstance(first_child, Leaf):
-            # Continue looking if we see a docstring; otherwise stop.
-            if (
-                len(child.children) == 2
-                and first_child.type == token.STRING
-                and child.children[1].type == token.NEWLINE
-            ):
-                continue
-            else:
-                break
-        elif first_child.type == syms.import_from:
-            module_name = first_child.children[1]
-            if not isinstance(module_name, Leaf) or module_name.value != "__future__":
-                break
-            imports |= set(get_imports_from_children(first_child.children[3:]))
-        else:
-            break
-    return imports
-
-
-def gen_python_files_in_dir(
-    path: Path,
-    root: Path,
-    include: Pattern[str],
-    exclude: Pattern[str],
-    report: "Report",
-) -> Iterator[Path]:
-    """Generate all files under `path` whose paths are not excluded by the
-    `exclude` regex, but are included by the `include` regex.
-
-    Symbolic links pointing outside of the `root` directory are ignored.
-
-    `report` is where output about exclusions goes.
-    """
-    assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
-    for child in path.iterdir():
-        try:
-            normalized_path = "/" + child.resolve().relative_to(root).as_posix()
-        except ValueError:
-            if child.is_symlink():
-                report.path_ignored(
-                    child, f"is a symbolic link that points outside {root}"
-                )
-                continue
-
-            raise
-
-        if child.is_dir():
-            normalized_path += "/"
-        exclude_match = exclude.search(normalized_path)
-        if exclude_match and exclude_match.group(0):
-            report.path_ignored(child, f"matches the --exclude regular expression")
-            continue
-
-        if child.is_dir():
-            yield from gen_python_files_in_dir(child, root, include, exclude, report)
-
-        elif child.is_file():
-            include_match = include.search(normalized_path)
-            if include_match:
-                yield child
-
-
-@lru_cache()
-def find_project_root(srcs: Iterable[str]) -> Path:
-    """Return a directory containing .git, .hg, or pyproject.toml.
-
-    That directory can be one of the directories passed in `srcs` or their
-    common parent.
-
-    If no directory in the tree contains a marker that would specify it's the
-    project root, the root of the file system is returned.
-    """
-    if not srcs:
-        return Path("/").resolve()
-
-    common_base = min(Path(src).resolve() for src in srcs)
-    if common_base.is_dir():
-        # Append a fake file so `parents` below returns `common_base_dir`, too.
-        common_base /= "fake-file"
-    for directory in common_base.parents:
-        if (directory / ".git").is_dir():
-            return directory
-
-        if (directory / ".hg").is_dir():
-            return directory
-
-        if (directory / "pyproject.toml").is_file():
-            return directory
-
-    return directory
-
-
-@dataclass
-class Report:
-    """Provides a reformatting counter. Can be rendered with `str(report)`."""
-
-    check: bool = False
-    quiet: bool = False
-    verbose: bool = False
-    change_count: int = 0
-    same_count: int = 0
-    failure_count: int = 0
-
-    def done(self, src: Path, changed: Changed) -> None:
-        """Increment the counter for successful reformatting. Write out a message."""
-        if changed is Changed.YES:
-            reformatted = "would reformat" if self.check else "reformatted"
-            if self.verbose or not self.quiet:
-                out(f"{reformatted} {src}")
-            self.change_count += 1
-        else:
-            if self.verbose:
-                if changed is Changed.NO:
-                    msg = f"{src} already well formatted, good job."
-                else:
-                    msg = f"{src} wasn't modified on disk since last run."
-                out(msg, bold=False)
-            self.same_count += 1
-
-    def failed(self, src: Path, message: str) -> None:
-        """Increment the counter for failed reformatting. Write out a message."""
-        err(f"error: cannot format {src}: {message}")
-        self.failure_count += 1
-
-    def path_ignored(self, path: Path, message: str) -> None:
-        if self.verbose:
-            out(f"{path} ignored: {message}", bold=False)
-
-    @property
-    def return_code(self) -> int:
-        """Return the exit code that the app should use.
-
-        This considers the current state of changed files and failures:
-        - if there were any failures, return 123;
-        - if any files were changed and --check is being used, return 1;
-        - otherwise return 0.
-        """
-        # According to http://tldp.org/LDP/abs/html/exitcodes.html starting with
-        # 126 we have special return codes reserved by the shell.
-        if self.failure_count:
-            return 123
-
-        elif self.change_count and self.check:
-            return 1
-
-        return 0
-
-    def __str__(self) -> str:
-        """Render a color report of the current state.
-
-        Use `click.unstyle` to remove colors.
-        """
-        if self.check:
-            reformatted = "would be reformatted"
-            unchanged = "would be left unchanged"
-            failed = "would fail to reformat"
-        else:
-            reformatted = "reformatted"
-            unchanged = "left unchanged"
-            failed = "failed to reformat"
-        report = []
-        if self.change_count:
-            s = "s" if self.change_count > 1 else ""
-            report.append(
-                click.style(f"{self.change_count} file{s} {reformatted}", bold=True)
-            )
-        if self.same_count:
-            s = "s" if self.same_count > 1 else ""
-            report.append(f"{self.same_count} file{s} {unchanged}")
-        if self.failure_count:
-            s = "s" if self.failure_count > 1 else ""
-            report.append(
-                click.style(f"{self.failure_count} file{s} {failed}", fg="red")
-            )
-        return ", ".join(report) + "."
-
-
-def parse_ast(src: str) -> Union[ast.AST, ast3.AST, ast27.AST]:
-    filename = "<unknown>"
-    if sys.version_info >= (3, 8):
-        # TODO: support Python 4+ ;)
-        for minor_version in range(sys.version_info[1], 4, -1):
-            try:
-                return ast.parse(src, filename, feature_version=(3, minor_version))
-            except SyntaxError:
-                continue
-    else:
-        for feature_version in (7, 6):
-            try:
-                return ast3.parse(src, filename, feature_version=feature_version)
-            except SyntaxError:
-                continue
-
-    return ast27.parse(src)
-
-
-def _fixup_ast_constants(
-    node: Union[ast.AST, ast3.AST, ast27.AST]
-) -> Union[ast.AST, ast3.AST, ast27.AST]:
-    """Map ast nodes deprecated in 3.8 to Constant."""
-    # casts are required until this is released:
-    # https://github.com/python/typeshed/pull/3142
-    if isinstance(node, (ast.Str, ast3.Str, ast27.Str, ast.Bytes, ast3.Bytes)):
-        return cast(ast.AST, ast.Constant(value=node.s))
-    elif isinstance(node, (ast.Num, ast3.Num, ast27.Num)):
-        return cast(ast.AST, ast.Constant(value=node.n))
-    elif isinstance(node, (ast.NameConstant, ast3.NameConstant)):
-        return cast(ast.AST, ast.Constant(value=node.value))
-    return node
-
-
-def assert_equivalent(src: str, dst: str) -> None:
-    """Raise AssertionError if `src` and `dst` aren't equivalent."""
-
-    def _v(node: Union[ast.AST, ast3.AST, ast27.AST], depth: int = 0) -> Iterator[str]:
-        """Simple visitor generating strings to compare ASTs by content."""
-
-        node = _fixup_ast_constants(node)
-
-        yield f"{'  ' * depth}{node.__class__.__name__}("
-
-        for field in sorted(node._fields):
-            # TypeIgnore has only one field 'lineno' which breaks this comparison
-            type_ignore_classes = (ast3.TypeIgnore, ast27.TypeIgnore)
-            if sys.version_info >= (3, 8):
-                type_ignore_classes += (ast.TypeIgnore,)
-            if isinstance(node, type_ignore_classes):
-                break
-
-            try:
-                value = getattr(node, field)
-            except AttributeError:
-                continue
-
-            yield f"{'  ' * (depth+1)}{field}="
-
-            if isinstance(value, list):
-                for item in value:
-                    # Ignore nested tuples within del statements, because we may insert
-                    # parentheses and they change the AST.
-                    if (
-                        field == "targets"
-                        and isinstance(node, (ast.Delete, ast3.Delete, ast27.Delete))
-                        and isinstance(item, (ast.Tuple, ast3.Tuple, ast27.Tuple))
-                    ):
-                        for item in item.elts:
-                            yield from _v(item, depth + 2)
-                    elif isinstance(item, (ast.AST, ast3.AST, ast27.AST)):
-                        yield from _v(item, depth + 2)
-
-            elif isinstance(value, (ast.AST, ast3.AST, ast27.AST)):
-                yield from _v(value, depth + 2)
-
-            else:
-                yield f"{'  ' * (depth+2)}{value!r},  # {value.__class__.__name__}"
-
-        yield f"{'  ' * depth})  # /{node.__class__.__name__}"
-
-    try:
-        src_ast = parse_ast(src)
-    except Exception as exc:
-        raise AssertionError(
-            f"cannot use --safe with this file; failed to parse source file.  "
-            f"AST error message: {exc}"
-        )
-
-    try:
-        dst_ast = parse_ast(dst)
-    except Exception as exc:
-        log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst)
-        raise AssertionError(
-            f"INTERNAL ERROR: Black produced invalid code: {exc}. "
-            f"Please report a bug on https://github.com/psf/black/issues.  "
-            f"This invalid output might be helpful: {log}"
-        ) from None
-
-    src_ast_str = "\n".join(_v(src_ast))
-    dst_ast_str = "\n".join(_v(dst_ast))
-    if src_ast_str != dst_ast_str:
-        log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
-        raise AssertionError(
-            f"INTERNAL ERROR: Black produced code that is not equivalent to "
-            f"the source.  "
-            f"Please report a bug on https://github.com/psf/black/issues.  "
-            f"This diff might be helpful: {log}"
-        ) from None
-
-
-def assert_stable(src: str, dst: str, mode: FileMode) -> None:
-    """Raise AssertionError if `dst` reformats differently the second time."""
-    newdst = format_str(dst, mode=mode)
-    if dst != newdst:
-        log = dump_to_file(
-            diff(src, dst, "source", "first pass"),
-            diff(dst, newdst, "first pass", "second pass"),
-        )
-        raise AssertionError(
-            f"INTERNAL ERROR: Black produced different code on the second pass "
-            f"of the formatter.  "
-            f"Please report a bug on https://github.com/psf/black/issues.  "
-            f"This diff might be helpful: {log}"
-        ) from None
-
-
-def dump_to_file(*output: str) -> str:
-    """Dump `output` to a temporary file. Return path to the file."""
-    with tempfile.NamedTemporaryFile(
-        mode="w", prefix="blk_", suffix=".log", delete=False, encoding="utf8"
-    ) as f:
-        for lines in output:
-            f.write(lines)
-            if lines and lines[-1] != "\n":
-                f.write("\n")
-    return f.name
-
-
-@contextmanager
-def nullcontext() -> Iterator[None]:
-    """Return context manager that does nothing.
-    Similar to `nullcontext` from python 3.7"""
-    yield
-
-
-def diff(a: str, b: str, a_name: str, b_name: str) -> str:
-    """Return a unified diff string between strings `a` and `b`."""
-    import difflib
-
-    a_lines = [line + "\n" for line in a.split("\n")]
-    b_lines = [line + "\n" for line in b.split("\n")]
-    return "".join(
-        difflib.unified_diff(a_lines, b_lines, fromfile=a_name, tofile=b_name, n=5)
-    )
-
-
-def cancel(tasks: Iterable[asyncio.Task]) -> None:
-    """asyncio signal handler that cancels all `tasks` and reports to stderr."""
-    err("Aborted!")
-    for task in tasks:
-        task.cancel()
-
-
-def shutdown(loop: asyncio.AbstractEventLoop) -> None:
-    """Cancel all pending tasks on `loop`, wait for them, and close the loop."""
-    try:
-        if sys.version_info[:2] >= (3, 7):
-            all_tasks = asyncio.all_tasks
-        else:
-            all_tasks = asyncio.Task.all_tasks
-        # This part is borrowed from asyncio/runners.py in Python 3.7b2.
-        to_cancel = [task for task in all_tasks(loop) if not task.done()]
-        if not to_cancel:
-            return
-
-        for task in to_cancel:
-            task.cancel()
-        loop.run_until_complete(
-            asyncio.gather(*to_cancel, loop=loop, return_exceptions=True)
-        )
-    finally:
-        # `concurrent.futures.Future` objects cannot be cancelled once they
-        # are already running. There might be some when the `shutdown()` happened.
-        # Silence their logger's spew about the event loop being closed.
-        cf_logger = logging.getLogger("concurrent.futures")
-        cf_logger.setLevel(logging.CRITICAL)
-        loop.close()
-
-
-def sub_twice(regex: Pattern[str], replacement: str, original: str) -> str:
-    """Replace `regex` with `replacement` twice on `original`.
-
-    This is used by string normalization to perform replaces on
-    overlapping matches.
-    """
-    return regex.sub(replacement, regex.sub(replacement, original))
-
-
-def re_compile_maybe_verbose(regex: str) -> Pattern[str]:
-    """Compile a regular expression string in `regex`.
-
-    If it contains newlines, use verbose mode.
-    """
-    if "\n" in regex:
-        regex = "(?x)" + regex
-    return re.compile(regex)
-
-
-def enumerate_reversed(sequence: Sequence[T]) -> Iterator[Tuple[Index, T]]:
-    """Like `reversed(enumerate(sequence))` if that were possible."""
-    index = len(sequence) - 1
-    for element in reversed(sequence):
-        yield (index, element)
-        index -= 1
-
-
-def enumerate_with_length(
-    line: Line, reversed: bool = False
-) -> Iterator[Tuple[Index, Leaf, int]]:
-    """Return an enumeration of leaves with their length.
-
-    Stops prematurely on multiline strings and standalone comments.
-    """
-    op = cast(
-        Callable[[Sequence[Leaf]], Iterator[Tuple[Index, Leaf]]],
-        enumerate_reversed if reversed else enumerate,
-    )
-    for index, leaf in op(line.leaves):
-        length = len(leaf.prefix) + len(leaf.value)
-        if "\n" in leaf.value:
-            return  # Multiline strings, we can't continue.
-
-        for comment in line.comments_after(leaf):
-            length += len(comment.value)
-
-        yield index, leaf, length
-
-
-def is_line_short_enough(line: Line, *, line_length: int, line_str: str = "") -> bool:
-    """Return True if `line` is no longer than `line_length`.
-
-    Uses the provided `line_str` rendering, if any, otherwise computes a new one.
-    """
-    if not line_str:
-        line_str = str(line).strip("\n")
-    return (
-        len(line_str) <= line_length
-        and "\n" not in line_str  # multiline strings
-        and not line.contains_standalone_comments()
-    )
-
-
-def can_be_split(line: Line) -> bool:
-    """Return False if the line cannot be split *for sure*.
-
-    This is not an exhaustive search but a cheap heuristic that we can use to
-    avoid some unfortunate formattings (mostly around wrapping unsplittable code
-    in unnecessary parentheses).
-    """
-    leaves = line.leaves
-    if len(leaves) < 2:
-        return False
-
-    if leaves[0].type == token.STRING and leaves[1].type == token.DOT:
-        call_count = 0
-        dot_count = 0
-        next = leaves[-1]
-        for leaf in leaves[-2::-1]:
-            if leaf.type in OPENING_BRACKETS:
-                if next.type not in CLOSING_BRACKETS:
-                    return False
-
-                call_count += 1
-            elif leaf.type == token.DOT:
-                dot_count += 1
-            elif leaf.type == token.NAME:
-                if not (next.type == token.DOT or next.type in OPENING_BRACKETS):
-                    return False
-
-            elif leaf.type not in CLOSING_BRACKETS:
-                return False
-
-            if dot_count > 1 and call_count > 1:
-                return False
-
-    return True
-
-
-def can_omit_invisible_parens(line: Line, line_length: int) -> bool:
-    """Does `line` have a shape safe to reformat without optional parens around it?
-
-    Returns True for only a subset of potentially nice looking formattings but
-    the point is to not return false positives that end up producing lines that
-    are too long.
-    """
-    bt = line.bracket_tracker
-    if not bt.delimiters:
-        # Without delimiters the optional parentheses are useless.
-        return True
-
-    max_priority = bt.max_delimiter_priority()
-    if bt.delimiter_count_with_priority(max_priority) > 1:
-        # With more than one delimiter of a kind the optional parentheses read better.
-        return False
-
-    if max_priority == DOT_PRIORITY:
-        # A single stranded method call doesn't require optional parentheses.
-        return True
-
-    assert len(line.leaves) >= 2, "Stranded delimiter"
-
-    first = line.leaves[0]
-    second = line.leaves[1]
-    penultimate = line.leaves[-2]
-    last = line.leaves[-1]
-
-    # With a single delimiter, omit if the expression starts or ends with
-    # a bracket.
-    if first.type in OPENING_BRACKETS and second.type not in CLOSING_BRACKETS:
-        remainder = False
-        length = 4 * line.depth
-        for _index, leaf, leaf_length in enumerate_with_length(line):
-            if leaf.type in CLOSING_BRACKETS and leaf.opening_bracket is first:
-                remainder = True
-            if remainder:
-                length += leaf_length
-                if length > line_length:
-                    break
-
-                if leaf.type in OPENING_BRACKETS:
-                    # There are brackets we can further split on.
-                    remainder = False
-
-        else:
-            # checked the entire string and line length wasn't exceeded
-            if len(line.leaves) == _index + 1:
-                return True
-
-        # Note: we are not returning False here because a line might have *both*
-        # a leading opening bracket and a trailing closing bracket.  If the
-        # opening bracket doesn't match our rule, maybe the closing will.
-
-    if (
-        last.type == token.RPAR
-        or last.type == token.RBRACE
-        or (
-            # don't use indexing for omitting optional parentheses;
-            # it looks weird
-            last.type == token.RSQB
-            and last.parent
-            and last.parent.type != syms.trailer
-        )
-    ):
-        if penultimate.type in OPENING_BRACKETS:
-            # Empty brackets don't help.
-            return False
-
-        if is_multiline_string(first):
-            # Additional wrapping of a multiline string in this situation is
-            # unnecessary.
-            return True
-
-        length = 4 * line.depth
-        seen_other_brackets = False
-        for _index, leaf, leaf_length in enumerate_with_length(line):
-            length += leaf_length
-            if leaf is last.opening_bracket:
-                if seen_other_brackets or length <= line_length:
-                    return True
-
-            elif leaf.type in OPENING_BRACKETS:
-                # There are brackets we can further split on.
-                seen_other_brackets = True
-
-    return False
-
-
-def get_cache_file(mode: FileMode) -> Path:
-    return CACHE_DIR / f"cache.{mode.get_cache_key()}.pickle"
-
-
-def read_cache(mode: FileMode) -> Cache:
-    """Read the cache if it exists and is well formed.
-
-    If it is not well formed, the call to write_cache later should resolve the issue.
-    """
-    cache_file = get_cache_file(mode)
-    if not cache_file.exists():
-        return {}
-
-    with cache_file.open("rb") as fobj:
-        try:
-            cache: Cache = pickle.load(fobj)
-        except pickle.UnpicklingError:
-            return {}
-
-    return cache
-
-
-def get_cache_info(path: Path) -> CacheInfo:
-    """Return the information used to check if a file is already formatted or not."""
-    stat = path.stat()
-    return stat.st_mtime, stat.st_size
-
-
-def filter_cached(cache: Cache, sources: Iterable[Path]) -> Tuple[Set[Path], Set[Path]]:
-    """Split an iterable of paths in `sources` into two sets.
-
-    The first contains paths of files that modified on disk or are not in the
-    cache. The other contains paths to non-modified files.
-    """
-    todo, done = set(), set()
-    for src in sources:
-        src = src.resolve()
-        if cache.get(src) != get_cache_info(src):
-            todo.add(src)
-        else:
-            done.add(src)
-    return todo, done
-
-
-def write_cache(cache: Cache, sources: Iterable[Path], mode: FileMode) -> None:
-    """Update the cache file."""
-    cache_file = get_cache_file(mode)
-    try:
-        CACHE_DIR.mkdir(parents=True, exist_ok=True)
-        new_cache = {**cache, **{src.resolve(): get_cache_info(src) for src in sources}}
-        with tempfile.NamedTemporaryFile(dir=str(cache_file.parent), delete=False) as f:
-            pickle.dump(new_cache, f, protocol=pickle.HIGHEST_PROTOCOL)
-        os.replace(f.name, cache_file)
-    except OSError:
-        pass
-
-
-def patch_click() -> None:
-    """Make Click not crash.
-
-    On certain misconfigured environments, Python 3 selects the ASCII encoding as the
-    default which restricts paths that it can access during the lifetime of the
-    application.  Click refuses to work in this scenario by raising a RuntimeError.
-
-    In case of Black the likelihood that non-ASCII characters are going to be used in
-    file paths is minimal since it's Python source code.  Moreover, this crash was
-    spurious on Python 3.7 thanks to PEP 538 and PEP 540.
-    """
-    try:
-        from click import core
-        from click import _unicodefun  # type: ignore
-    except ModuleNotFoundError:
-        return
-
-    for module in (core, _unicodefun):
-        if hasattr(module, "_verify_python3_env"):
-            module._verify_python3_env = lambda: None
-
-
-def patched_main() -> None:
-    freeze_support()
-    patch_click()
-    main()
-
-
-if __name__ == "__main__":
-    patched_main()
--- a/tests/test-check-code.t	Tue Oct 29 10:43:47 2019 +0100
+++ b/tests/test-check-code.t	Tue Oct 29 11:07:25 2019 +0100
@@ -21,7 +21,6 @@
   Skipping contrib/automation/hgautomation/try_server.py it has no-che?k-code (glob)
   Skipping contrib/automation/hgautomation/windows.py it has no-che?k-code (glob)
   Skipping contrib/automation/hgautomation/winrm.py it has no-che?k-code (glob)
-  Skipping contrib/grey.py it has no-che?k-code (glob)
   Skipping contrib/packaging/hgpackaging/downloads.py it has no-che?k-code (glob)
   Skipping contrib/packaging/hgpackaging/inno.py it has no-che?k-code (glob)
   Skipping contrib/packaging/hgpackaging/py2exe.py it has no-che?k-code (glob)
--- a/tests/test-check-format.t	Tue Oct 29 10:43:47 2019 +0100
+++ b/tests/test-check-format.t	Tue Oct 29 11:07:25 2019 +0100
@@ -1,5 +1,5 @@
 #require black
 
   $ cd $RUNTESTDIR/..
-  $ black --config=black.toml --check --diff `hg files 'set:**.py - hgext/fsmonitor/pywatchman/** - mercurial/thirdparty/** - "contrib/python-zstandard/**" - contrib/grey.py'`
+  $ black --config=black.toml --check --diff `hg files 'set:**.py - hgext/fsmonitor/pywatchman/** - mercurial/thirdparty/** - "contrib/python-zstandard/**"'`
 
--- a/tests/test-check-module-imports.t	Tue Oct 29 10:43:47 2019 +0100
+++ b/tests/test-check-module-imports.t	Tue Oct 29 11:07:25 2019 +0100
@@ -20,7 +20,6 @@
   > -X setup.py \
   > -X contrib/automation/ \
   > -X contrib/debugshell.py \
-  > -X contrib/grey.py \
   > -X contrib/hgweb.fcgi \
   > -X contrib/packaging/hg-docker \
   > -X contrib/packaging/hgpackaging/ \
--- a/tests/test-check-py3-compat.t	Tue Oct 29 10:43:47 2019 +0100
+++ b/tests/test-check-py3-compat.t	Tue Oct 29 11:07:25 2019 +0100
@@ -6,7 +6,6 @@
 #if no-py3
   $ testrepohg files 'set:(**.py)' \
   > -X contrib/automation/ \
-  > -X contrib/grey.py \
   > -X contrib/packaging/hgpackaging/ \
   > -X contrib/packaging/inno/ \
   > -X contrib/packaging/wix/ \