procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
# Helper script used for generating history and working copy files and content.
# The file's name corresponds to its history. The number of changesets can
# be specified on the command line. With 2 changesets, files with names like
# content1_content2_content1-untracked are generated. The first two filename
# segments describe the contents in the two changesets. The third segment
# ("content1-untracked") describes the state in the working copy, i.e.
# the file has content "content1" and is untracked (since it was previously
# tracked, it has been forgotten).
#
# This script generates the filenames and their content, but it's up to the
# caller to tell hg about the state.
#
# There are two subcommands:
# filelist <numchangesets>
# state <numchangesets> (<changeset>|wc)
#
# Typical usage:
#
# $ python $TESTDIR/generate-working-copy-states.py state 2 1
# $ hg addremove --similarity 0
# $ hg commit -m 'first'
#
# $ python $TESTDIR/generate-working-copy-states.py state 2 1
# $ hg addremove --similarity 0
# $ hg commit -m 'second'
#
# $ python $TESTDIR/generate-working-copy-states.py state 2 wc
# $ hg addremove --similarity 0
# $ hg forget *_*_*-untracked
# $ rm *_*_missing-*
import os
import sys
# Generates pairs of (filename, contents), where 'contents' is a list
# describing the file's content at each revision (or in the working copy).
# At each revision, it is either None or the file's actual content. When not
# None, it may be either new content or the same content as an earlier
# revisions, so all of (modified,clean,added,removed) can be tested.
def generatestates(maxchangesets, parentcontents):
depth = len(parentcontents)
if depth == maxchangesets + 1:
for tracked in (b'untracked', b'tracked'):
filename = (
b"_".join(
[
(content is None and b'missing' or content)
for content in parentcontents
]
)
+ b"-"
+ tracked
)
yield (filename, parentcontents)
else:
for content in {None, b'content' + (b"%d" % (depth + 1))} | set(
parentcontents
):
for combination in generatestates(
maxchangesets, parentcontents + [content]
):
yield combination
# retrieve the command line arguments
target = sys.argv[1]
maxchangesets = int(sys.argv[2])
if target == 'state':
depth = sys.argv[3]
# sort to make sure we have stable output
combinations = sorted(generatestates(maxchangesets, []))
# compute file content
content = []
for filename, states in combinations:
if target == 'filelist':
print(filename.decode('ascii'))
elif target == 'state':
if depth == 'wc':
# Make sure there is content so the file gets written and can be
# tracked. It will be deleted outside of this script.
content.append((filename, states[maxchangesets] or b'TOBEDELETED'))
else:
content.append((filename, states[int(depth) - 1]))
else:
print("unknown target:", target, file=sys.stderr)
sys.exit(1)
# write actual content
for filename, data in content:
if data is not None:
f = open(filename, 'wb')
f.write(data + b'\n')
f.close()
elif os.path.exists(filename):
os.remove(filename)