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.
$ cat >> $HGRCPATH << EOF
> [extensions]
> fastannotate=
> [fastannotate]
> mainbranch=main
> EOF
$ hg init repo
$ cd repo
add or rename files on top of the master branch
$ echo a1 > a
$ echo b1 > b
$ hg commit -qAm 1
$ hg bookmark -i main
$ hg fastannotate --debug -nf b
fastannotate: b: 1 new changesets in the main branch
0 b: b1
$ hg fastannotate --debug -nf a
fastannotate: a: 1 new changesets in the main branch
0 a: a1
$ echo a2 >> a
$ cat > b << EOF
> b0
> b1
> EOF
$ hg mv a t
$ hg mv b a
$ hg mv t b
$ hg commit -m 'swap names'
existing linelogs are not helpful with such renames in side branches
$ hg fastannotate --debug -nf a
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
$ hg fastannotate --debug -nf b
fastannotate: b: linelog cannot help in annotating this revision
0 a: a1
1 b: a2
move main branch forward, rebuild should happen
$ hg bookmark -i main -r . -q
$ hg fastannotate --debug -nf b
fastannotate: b: cache broken and deleted
fastannotate: b: 2 new changesets in the main branch
0 a: a1
1 b: a2
$ hg fastannotate --debug -nf b
fastannotate: b: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
for rev 0, the existing linelog is still useful for a, but not for b
$ hg fastannotate --debug -nf a -r 0
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
$ hg fastannotate --debug -nf b -r 0
fastannotate: b: linelog cannot help in annotating this revision
0 b: b1
a rebuild can also be triggered if "the main branch last time" mismatches
$ echo a3 >> a
$ hg commit -m a3
$ cat >> b << EOF
> b3
> b4
> EOF
$ hg commit -m b4
$ hg bookmark -i main -q
$ hg fastannotate --debug -nf a
fastannotate: a: cache broken and deleted
fastannotate: a: 3 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a
fastannotate: a: using fast path (resolved fctx: True)
1 a: b0
0 b: b1
2 a: a3
linelog can be updated without being helpful
$ hg mv a t
$ hg mv b a
$ hg mv t b
$ hg commit -m 'swap names again'
$ hg fastannotate --debug -nf b
fastannotate: b: 1 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf b
fastannotate: b: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
move main branch forward again, rebuilds are one-time
$ hg bookmark -i main -q
$ hg fastannotate --debug -nf a
fastannotate: a: cache broken and deleted
fastannotate: a: 4 new changesets in the main branch
0 a: a1
1 b: a2
3 b: b3
3 b: b4
$ hg fastannotate --debug -nf b
fastannotate: b: cache broken and deleted
fastannotate: b: 4 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
3 b: b3
3 b: b4
$ hg fastannotate --debug -nf b
fastannotate: b: using fast path (resolved fctx: True)
1 a: b0
0 b: b1
2 a: a3
list changeset hashes to improve readability
$ hg log -T '{rev}:{node}\n'
4:980e1ab8c516350172928fba95b49ede3b643dca
3:14e123fedad9f491f5dde0beca2a767625a0a93a
2:96495c41e4c12218766f78cdf244e768d7718b0f
1:35c2b781234c994896aba36bd3245d3104e023df
0:653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f
annotate a revision not in the linelog. linelog cannot be used, but does not get rebuilt either
$ hg fastannotate --debug -nf a -r 96495c41e4c12218766f78cdf244e768d7718b0f
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a -r 2
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a -r .
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
3 b: b3
3 b: b4
annotate an ancient revision where the path matches. linelog can be used
$ hg fastannotate --debug -nf a -r 0
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
$ hg fastannotate --debug -nf a -r 653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f
fastannotate: a: using fast path (resolved fctx: False)
0 a: a1