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.
$ hg init
$ echo foo > a
$ echo foo > b
$ hg add a b
$ hg ci -m "test"
$ echo blah > a
$ hg ci -m "branch a"
$ hg co 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo blah > b
$ hg ci -m "branch b"
created new head
$ HGMERGE=true hg merge 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m "merge b/a -> blah"
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ HGMERGE=true hg merge 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m "merge a/b -> blah"
created new head
$ hg log
changeset: 4:2ee31f665a86
tag: tip
parent: 1:96155394af80
parent: 2:92cc4c306b19
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge a/b -> blah
changeset: 3:e16a66a37edd
parent: 2:92cc4c306b19
parent: 1:96155394af80
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge b/a -> blah
changeset: 2:92cc4c306b19
parent: 0:5e0375449e74
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: branch b
changeset: 1:96155394af80
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: branch a
changeset: 0:5e0375449e74
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: test
$ hg debugindex --changelog
rev linkrev nodeid p1-nodeid p2-nodeid
0 0 5e0375449e74 000000000000 000000000000
1 1 96155394af80 5e0375449e74 000000000000
2 2 92cc4c306b19 5e0375449e74 000000000000
3 3 e16a66a37edd 92cc4c306b19 96155394af80
4 4 2ee31f665a86 96155394af80 92cc4c306b19
revision 1
$ hg manifest --debug 1
79d7492df40aa0fa093ec4209be78043c181f094 644 a
2ed2a3912a0b24502043eae84ee4b279c18b90dd 644 b
revision 2
$ hg manifest --debug 2
2ed2a3912a0b24502043eae84ee4b279c18b90dd 644 a
79d7492df40aa0fa093ec4209be78043c181f094 644 b
revision 3
$ hg manifest --debug 3
79d7492df40aa0fa093ec4209be78043c181f094 644 a
79d7492df40aa0fa093ec4209be78043c181f094 644 b
revision 4
$ hg manifest --debug 4
79d7492df40aa0fa093ec4209be78043c181f094 644 a
79d7492df40aa0fa093ec4209be78043c181f094 644 b
$ hg debugindex a
rev linkrev nodeid p1-nodeid p2-nodeid
0 0 2ed2a3912a0b 000000000000 000000000000
1 1 79d7492df40a 2ed2a3912a0b 000000000000
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 5 changesets with 4 changes to 2 files