demandimport: fix a crash in LazyFinder.__delattr__ I was tinkering with `with hgdemandimport.deactivated()` wrapped around loading the keyring module, and got spew that seemed to be confirmed by PyCharm. But I can't believe we haven't seen this before (and phabricator uses the same pattern): ** Unknown exception encountered with possibly-broken third-party extension "mercurial_keyring" 1.4.3 (keyring 23.11.0, backend unknown) ** which supports versions unknown of Mercurial. ** Please disable "mercurial_keyring" and try your action again. ** If that fixes the bug please report it to https://foss.heptapod.net/mercurial/mercurial_keyring/issues ** Python 3.9.15 (main, Oct 13 2022, 04:28:25) [GCC 7.5.0] ** Mercurial Distributed SCM (version 6.3.1) ** Extensions loaded: absorb, attorc 20220315, blackbox, eol, extdiff, fastannotate, lfs, mercurial_keyring 1.4.3 (keyring 23.11.0, backend unknown), phabblocker 20220315, phabricator 20220315, purge, rebase, schemes, share, show, strip, uncommit Traceback (most recent call last): File "/usr/local/bin/hg", line 59, in <module> dispatch.run() File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 143, in run status = dispatch(req) File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 232, in dispatch status = _rundispatch(req) File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 276, in _rundispatch ret = _runcatch(req) or 0 File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 451, in _runcatch return _callcatch(ui, _runcatchfunc) File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 461, in _callcatch return scmutil.callcatch(ui, func) File "/usr/local/lib/python3.9/site-packages/mercurial/scmutil.py", line 153, in callcatch return func() File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 441, in _runcatchfunc return _dispatch(req) File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1265, in _dispatch return runcommand( File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 899, in runcommand ret = _runcommand(ui, options, cmd, d) File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1277, in _runcommand return cmdfunc() File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1263, in <lambda> d = lambda: util.checksignature(func)(ui, *args, **strcmdopt) File "/usr/local/lib/python3.9/site-packages/mercurial/util.py", line 1880, in check return func(*args, **kwargs) File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 962, in cmd_keyring_check user, pwd, source, final_url = handler.get_credentials( File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 497, in get_credentials keyring_pwd = password_store.get_http_password(keyring_url, actual_user) File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 287, in get_http_password return self._read_password_from_keyring( File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 335, in _read_password_from_keyring keyring = import_keyring() >> `with hgdemandimport.deactivated()` inserted here File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 120, in import_keyring return _import_keyring() File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 133, in _import_keyring mod, was_imported_now = meu.direct_import_ext( File "/usr/lib/python3.9/site-packages/mercurial_extension_utils.py", line 1381, in direct_import_ext __import__(module_name) File "<frozen importlib._bootstrap>", line 1007, in _find_and_load File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 680, in _load_unlocked File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module self.loader.exec_module(module) File "/usr/lib/python3.9/site-packages/keyring/__init__.py", line 1, in <module> from .core import ( File "<frozen importlib._bootstrap>", line 1007, in _find_and_load File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 680, in _load_unlocked File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module self.loader.exec_module(module) File "/usr/lib/python3.9/site-packages/keyring/core.py", line 11, in <module> from . import backend, credentials File "<frozen importlib._bootstrap>", line 1007, in _find_and_load File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 680, in _load_unlocked File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module self.loader.exec_module(module) File "/usr/lib/python3.9/site-packages/keyring/backend.py", line 13, in <module> from .py312compat import metadata File "<frozen importlib._bootstrap>", line 1007, in _find_and_load File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 680, in _load_unlocked File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module self.loader.exec_module(module) File "/usr/lib/python3.9/site-packages/keyring/py312compat.py", line 10, in <module> import importlib_metadata as metadata # type: ignore File "<frozen importlib._bootstrap>", line 1007, in _find_and_load File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 680, in _load_unlocked File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module self.loader.exec_module(module) File "/usr/lib/python3.9/site-packages/importlib_metadata/__init__.py", line 715, in <module> class MetadataPathFinder(NullFinder, DistributionFinder): File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 24, in install disable_stdlib_finder() File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 43, in disable_stdlib_finder del finder.find_distributions File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 88, in __delattr__ return delattr(object.__getattribute__(self, "_finder")) TypeError: delattr expected 2 arguments, got 1

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# demandimportpy3 - global demand-loading of modules for Mercurial

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#

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# Copyright 2017 Facebook Inc.

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#

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# This software may be used and distributed according to the terms of the

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# GNU General Public License version 2 or any later version.

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     8

"""Lazy loading for Python 3.6 and above.

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This uses the new importlib finder/loader functionality available in Python 3.5

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and up. The code reuses most of the mechanics implemented inside importlib.util,

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but with a few additions:

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* Allow excluding certain modules from lazy imports.

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* Expose an interface that's substantially the same as demandimport for

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  Python 2.

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This also has some limitations compared to the Python 2 implementation:

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* Much of the logic is per-package, not per-module, so any packages loaded

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  before demandimport is enabled will not be lazily imported in the future. In

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  practice, we only expect builtins to be loaded before demandimport is

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  enabled.

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"""

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# This line is unnecessary, but it satisfies test-check-py3-compat.t.

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import contextlib

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import importlib.util

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import sys

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from . import tracing

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_deactivated = False

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class _lazyloaderex(importlib.util.LazyLoader):

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    """This is a LazyLoader except it also follows the _deactivated global and

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    the ignore list.

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    """

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    def exec_module(self, module):

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        """Make the module load lazily."""

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        with tracing.log('demandimport %s', module):

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            if _deactivated or module.__name__ in ignores:

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                self.loader.exec_module(module)

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            else:

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                super().exec_module(module)

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class LazyFinder:

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    """A wrapper around a ``MetaPathFinder`` that makes loaders lazy.

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    ``sys.meta_path`` finders have their ``find_spec()`` called to locate a

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    module. This returns a ``ModuleSpec`` if found or ``None``. The

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    ``ModuleSpec`` has a ``loader`` attribute, which is called to actually

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    load a module.

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    Our class wraps an existing finder and overloads its ``find_spec()`` to

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    replace the ``loader`` with our lazy loader proxy.

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    We have to use __getattribute__ to proxy the instance because some meta

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    path finders don't support monkeypatching.

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    """

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    __slots__ = ("_finder",)

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    def __init__(self, finder):

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        object.__setattr__(self, "_finder", finder)

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    def __repr__(self):

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        return "<LazyFinder for %r>" % object.__getattribute__(self, "_finder")

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    # __bool__ is canonical Python 3. But check-code insists on __nonzero__ being

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    # defined via `def`.

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    def __nonzero__(self):

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        return bool(object.__getattribute__(self, "_finder"))

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    __bool__ = __nonzero__

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    def __getattribute__(self, name):

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        if name in ("_finder", "find_spec"):

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            return object.__getattribute__(self, name)

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    85

        return getattr(object.__getattribute__(self, "_finder"), name)

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    def __delattr__(self, name):

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        return delattr(object.__getattribute__(self, "_finder"), name)

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    def __setattr__(self, name, value):

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        return setattr(object.__getattribute__(self, "_finder"), name, value)

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    93

    def find_spec(self, fullname, path, target=None):

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        finder = object.__getattribute__(self, "_finder")

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        try:

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            find_spec = finder.find_spec

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        except AttributeError:

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            loader = finder.find_module(fullname, path)

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            if loader is None:

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                spec = None

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            else:

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                spec = importlib.util.spec_from_loader(fullname, loader)

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        else:

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            spec = find_spec(fullname, path, target)

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        # Lazy loader requires exec_module().

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        if (

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            spec is not None

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            and spec.loader is not None

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            and getattr(spec.loader, "exec_module", None)

   111

        ):

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            spec.loader = _lazyloaderex(spec.loader)

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        return spec

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   116

   117

ignores = set()

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   119

   120

def init(ignoreset):

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    global ignores

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    ignores = ignoreset

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   124

   125

def isenabled():

   126

    return not _deactivated and any(

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        isinstance(finder, LazyFinder) for finder in sys.meta_path

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    )

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   130

   131

def disable():

   132

    new_finders = []

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    for finder in sys.meta_path:

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        new_finders.append(

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            finder._finder if isinstance(finder, LazyFinder) else finder

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        )

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    sys.meta_path[:] = new_finders

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   139

   140

def enable():

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    new_finders = []

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    for finder in sys.meta_path:

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        new_finders.append(

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            LazyFinder(finder) if not isinstance(finder, LazyFinder) else finder

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        )

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    sys.meta_path[:] = new_finders

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   148

   149

@contextlib.contextmanager

   150

def deactivated():

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    # This implementation is a bit different from Python 2's. Python 3

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    # maintains a per-package finder cache in sys.path_importer_cache (see

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    # PEP 302). This means that we can't just call disable + enable.

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    # If we do that, in situations like:

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    #

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    #   demandimport.enable()

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    #   ...

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    #   from foo.bar import mod1

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    #   with demandimport.deactivated():

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    #       from foo.bar import mod2

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    #

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    # mod2 will be imported lazily. (The converse also holds -- whatever finder

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    # first gets cached will be used.)

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    #

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    # Instead, have a global flag the LazyLoader can use.

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    global _deactivated

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    demandenabled = isenabled()

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    if demandenabled:

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        _deactivated = True

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    try:

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        yield

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    finally:

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        if demandenabled:

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            _deactivated = False