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.
#!/bin/bash
#
# produces two repositories with different common and missing subsets
#
# $ discovery-helper.sh REPO NBHEADS DEPT
#
# The Goal is to produce two repositories with some common part and some
# exclusive part on each side. Provide a source repository REPO, it will
# produce two repositories REPO-left and REPO-right.
#
# Each repository will be missing some revisions exclusive to NBHEADS of the
# repo topological heads. These heads and revisions exclusive to them (up to
# DEPTH depth) are stripped.
#
# The "left" repository will use the NBHEADS first heads (sorted by
# description). The "right" use the last NBHEADS one.
#
# To find out how many topological heads a repo has, use:
#
# $ hg heads -t -T '{rev}\n' | wc -l
#
# Example:
#
# The `pypy-2018-09-01` repository has 192 heads. To produce two repositories
# with 92 common heads and ~50 exclusive heads on each side.
#
# $ ./discovery-helper.sh pypy-2018-08-01 50 10
set -euo pipefail
printusage () {
echo "usage: `basename $0` REPO NBHEADS DEPTH [left|right]" >&2
}
if [ $# -lt 3 ]; then
printusage
exit 64
fi
repo="$1"
shift
nbheads="$1"
shift
depth="$1"
shift
doleft=1
doright=1
if [ $# -gt 1 ]; then
printusage
exit 64
elif [ $# -eq 1 ]; then
if [ "$1" == "left" ]; then
doleft=1
doright=0
elif [ "$1" == "right" ]; then
doleft=0
doright=1
else
printusage
exit 64
fi
fi
leftrepo="${repo}-${nbheads}h-${depth}d-left"
rightrepo="${repo}-${nbheads}h-${depth}d-right"
left="first(sort(heads(all()), 'desc'), $nbheads)"
right="last(sort(heads(all()), 'desc'), $nbheads)"
leftsubset="ancestors($left, $depth) and only($left, heads(all() - $left))"
rightsubset="ancestors($right, $depth) and only($right, heads(all() - $right))"
echo '### creating left/right repositories with missing changesets:'
if [ $doleft -eq 1 ]; then
echo '# left revset:' '"'${leftsubset}'"'
fi
if [ $doright -eq 1 ]; then
echo '# right revset:' '"'${rightsubset}'"'
fi
buildone() {
side="$1"
dest="$2"
revset="$3"
echo "### building $side repository: $dest"
if [ -e "$dest" ]; then
echo "destination repo already exists: $dest" >&2
exit 1
fi
echo '# cloning'
if ! cp --recursive --reflink=always ${repo} ${dest}; then
hg clone --noupdate "${repo}" "${dest}"
fi
echo '# stripping' '"'${revset}'"'
hg -R "${dest}" --config extensions.strip= strip --rev "$revset" --no-backup
}
if [ $doleft -eq 1 ]; then
buildone left "$leftrepo" "$leftsubset"
fi
if [ $doright -eq 1 ]; then
buildone right "$rightrepo" "$rightsubset"
fi