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/sh
# Script to get stable diff output on any platform.
#
# Output of this script is almost equivalent to GNU diff with "-Nru".
#
# Use this script as "hg pdiff" via extdiff extension with preparation
# below in test scripts:
#
# $ cat >> $HGRCPATH <<EOF
# > [extdiff]
# > pdiff = sh "$RUNTESTDIR/pdiff"
# > EOF
filediff(){
# USAGE: filediff file1 file2 [header]
# compare with /dev/null if file doesn't exist (as "-N" option)
file1="$1"
if test ! -f "$file1"; then
file1=/dev/null
fi
file2="$2"
if test ! -f "$file2"; then
file2=/dev/null
fi
if cmp -s "$file1" "$file2" 2> /dev/null; then
# Return immediately, because comparison isn't needed. This
# also avoids redundant message of diff like "No differences
# encountered" (on Solaris)
return
fi
if test -n "$3"; then
# show header only in recursive case
echo "$3"
fi
# replace "/dev/null" by corresponded filename (as "-N" option)
diff -u "$file1" "$file2" |
sed "s@^--- /dev/null\(.*\)\$@--- $1\1@" |
sed "s@^\+\+\+ /dev/null\(.*\)\$@+++ $2\1@"
# in this case, files differ from each other
return 1
}
if test -d "$1" -o -d "$2"; then
# ensure comparison in dictionary order
(
if test -d "$1"; then (cd "$1" && find . -type f); fi
if test -d "$2"; then (cd "$2" && find . -type f); fi
) |
sed 's@^\./@@g' | sort | uniq |
while read file; do
filediff "$1/$file" "$2/$file" "diff -Nru $1/$file $2/$file"
done
# TODO: there is no portable way for current while-read based
# implementation to return 1 at detecting changes.
#
# On bash and dash, assignment to variable inside while-block
# doesn't affect outside, because inside while-block is executed
# in sub-shell. BTW, it affects outside while-block on ksh (as sh
# on Solaris).
else
filediff "$1" "$2"
fi