tests/filtertraceback.py

procutil: back out 8403cc54bc83 (make ....procutil.stderr unbuffered)

Changeset 8403cc54bc83 introduced code that opens a second file object
referring to the stderr file descriptor. This broke tests on Windows. The
reason is that on Windows, sys.stderr is buffered and procutil.stderr closed
the file descriptor when it got garbage collected before sys.stderr had the
chance to flush buffered data.

`procutil.stdout` had the same problem for a long time, but we didn’t realize,
as in CI test runs, stdout is not a TTY and in this case no second file object
is opened.

#!/usr/bin/env python

# Filters traceback lines from stdin.

from __future__ import absolute_import, print_function

import io
import sys

if sys.version_info[0] >= 3:
    # Prevent \r from being inserted on Windows.
    sys.stdout = io.TextIOWrapper(
        sys.stdout.buffer,
        sys.stdout.encoding,
        sys.stdout.errors,
        newline="\n",
        line_buffering=sys.stdout.line_buffering,
    )

state = 'none'

for line in sys.stdin:
    if state == 'none':
        if line.startswith('Traceback '):
            state = 'tb'

    elif state == 'tb':
        if line.startswith('  File '):
            state = 'file'
            continue

        elif not line.startswith(' '):
            state = 'none'

    elif state == 'file':
        # Ignore lines after "  File "
        state = 'tb'
        continue

    print(line, end='')