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.
#testcases skip-detection fail-if-detected
Test situations that "should" only be reproducible:
- on networked filesystems, or
- user using `hg debuglocks` to eliminate the lock file, or
- something (that doesn't respect the lock file) writing to the .hg directory
while we're running
$ hg init a
$ cd a
$ cat > "$TESTTMP_FORWARD_SLASH/waitlock_editor.sh" <<EOF
> [ -n "\${WAITLOCK_ANNOUNCE:-}" ] && touch "\${WAITLOCK_ANNOUNCE}"
> f="\${WAITLOCK_FILE}"
> start=\`date +%s\`
> timeout=5
> "$RUNTESTDIR_FORWARD_SLASH/testlib/wait-on-file" "\$timeout" "\$f"
> if [ \$# -gt 1 ]; then
> cat "\$@"
> fi
> EOF
Things behave differently if we don't already have a 00changelog.i file when
this all starts, so let's make one.
$ echo r0 > r0
$ hg commit -qAm 'r0'
Start an hg commit that will take a while
$ EDITOR_STARTED="$TESTTMP_FORWARD_SLASH/a/.editor_started"
$ MISCHIEF_MANAGED="$TESTTMP_FORWARD_SLASH/a/.mischief_managed"
$ JOBS_FINISHED="$TESTTMP_FORWARD_SLASH/a/.jobs_finished"
#if fail-if-detected
$ cat >> .hg/hgrc << EOF
> [debug]
> revlog.verifyposition.changelog = fail
> EOF
#endif
$ cat >> .hg/hgrc << EOF
> [ui]
> editor=sh $TESTTMP_FORWARD_SLASH/waitlock_editor.sh
> EOF
$ echo foo > foo
$ (unset HGEDITOR;
> WAITLOCK_ANNOUNCE="${EDITOR_STARTED}" \
> WAITLOCK_FILE="${MISCHIEF_MANAGED}" \
> hg commit -qAm 'r1 (foo)' --edit foo > .foo_commit_out 2>&1 ; touch "${JOBS_FINISHED}") &
Wait for the "editor" to actually start
$ sh "$RUNTESTDIR_FORWARD_SLASH/testlib/wait-on-file" 5 "${EDITOR_STARTED}"
$ cat >> .hg/hgrc << EOF
> [ui]
> editor=
> EOF
Break the locks, and make another commit.
$ hg debuglocks -LW
$ echo bar > bar
$ hg commit -qAm 'r2 (bar)' bar
$ hg debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000
Awaken the editor from that first commit
$ touch "${MISCHIEF_MANAGED}"
And wait for it to finish
$ WAITLOCK_FILE="${JOBS_FINISHED}" sh "$TESTTMP_FORWARD_SLASH/waitlock_editor.sh"
#if skip-detection
(Ensure there was no output)
$ cat .foo_commit_out
And observe a corrupted repository -- rev 2's linkrev is 1, which should never
happen for the changelog (the linkrev should always refer to itself).
$ hg debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000
2 1 ac80e6205bb2 222799e2f90b 000000000000
#endif
#if fail-if-detected
$ cat .foo_commit_out
transaction abort!
rollback completed
note: commit message saved in .hg/last-message.txt
note: use 'hg commit --logfile .hg/last-message.txt --edit' to reuse it
abort: 00changelog.i: file cursor at position 249, expected 121
And no corruption in the changelog.
$ hg debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000 (missing-correct-output !)
And, because of transactions, there's none in the manifestlog either.
$ hg debugrevlogindex -m
rev linkrev nodeid p1 p2
0 0 7b7020262a56 000000000000 000000000000
1 1 ad3fe36d86d9 7b7020262a56 000000000000
#endif