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.
# reproduce issue2264, issue2516
create test repo
$ cat <<EOF >> $HGRCPATH
> [extensions]
> transplant =
> EOF
$ hg init repo
$ cd repo
$ template="{rev} {desc|firstline} [{branch}]\n"
# we need to start out with two changesets on the default branch
# in order to avoid the cute little optimization where transplant
# pulls rather than transplants
add initial changesets
$ echo feature1 > file1
$ hg ci -Am"feature 1"
adding file1
$ echo feature2 >> file2
$ hg ci -Am"feature 2"
adding file2
# The changes to 'bugfix' are enough to show the bug: in fact, with only
# those changes, it's a very noisy crash ("RuntimeError: nothing
# committed after transplant"). But if we modify a second file in the
# transplanted changesets, the bug is much more subtle: transplant
# silently drops the second change to 'bugfix' on the floor, and we only
# see it when we run 'hg status' after transplanting. Subtle data loss
# bugs are worse than crashes, so reproduce the subtle case here.
commit bug fixes on bug fix branch
$ hg branch fixes
marked working directory as branch fixes
(branches are permanent and global, did you want a bookmark?)
$ echo fix1 > bugfix
$ echo fix1 >> file1
$ hg ci -Am"fix 1"
adding bugfix
$ echo fix2 > bugfix
$ echo fix2 >> file1
$ hg ci -Am"fix 2"
$ hg log -G --template="$template"
@ 3 fix 2 [fixes]
|
o 2 fix 1 [fixes]
|
o 1 feature 2 [default]
|
o 0 feature 1 [default]
transplant bug fixes onto release branch
$ hg update 0
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg branch release
marked working directory as branch release
$ hg transplant 2 3
applying [0-9a-f]{12} (re)
[0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
applying [0-9a-f]{12} (re)
[0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
$ hg log -G --template="$template"
@ 5 fix 2 [release]
|
o 4 fix 1 [release]
|
| o 3 fix 2 [fixes]
| |
| o 2 fix 1 [fixes]
| |
| o 1 feature 2 [default]
|/
o 0 feature 1 [default]
$ hg status
$ hg status --rev 0:4
M file1
A bugfix
$ hg status --rev 4:5
M bugfix
M file1
now test that we fixed the bug for all scripts/extensions
$ cat > $TESTTMP/committwice.py <<__EOF__
> import time
> from mercurial import hg, match, node, ui as uimod
>
> def replacebyte(fn, b):
> f = open(fn, "rb+")
> f.seek(0, 0)
> f.write(b)
> f.close()
>
> def printfiles(repo, rev):
> repo.ui.status(b"revision %d files: [%s]\n"
> % (rev, b', '.join(b"'%s'" % f
> for f in repo[rev].files())))
>
> repo = hg.repository(uimod.ui.load(), b'.')
> assert len(repo) == 6, "initial: len(repo): %d, expected: 6" % len(repo)
>
> replacebyte(b"bugfix", b"u")
> time.sleep(2)
> try:
> repo.ui.status(b"PRE: len(repo): %d\n" % len(repo))
> wlock = repo.wlock()
> lock = repo.lock()
> replacebyte(b"file1", b"x")
> repo.commit(text=b"x", user=b"test", date=(0, 0))
> replacebyte(b"file1", b"y")
> repo.commit(text=b"y", user=b"test", date=(0, 0))
> repo.ui.status(b"POST: len(repo): %d\n" % len(repo))
> finally:
> lock.release()
> wlock.release()
> printfiles(repo, 6)
> printfiles(repo, 7)
> __EOF__
$ "$PYTHON" $TESTTMP/committwice.py
PRE: len(repo): 6
POST: len(repo): 8
revision 6 files: ['bugfix', 'file1']
revision 7 files: ['file1']
Do a size-preserving modification outside of that process
$ echo abcd > bugfix
$ hg status
M bugfix
$ hg log --template "{rev} {desc} {files}\n" -r5:
5 fix 2 bugfix file1
6 x bugfix file1
7 y file1
$ cd ..