view contrib/debugcmdserver.py @ 48185:2f2107c01dee

dispatch: ignore failure to flush ui

When the pager dies, we get a `SIGPIPE`. That causes
`error.SignalInterrupt` to be raised ` (from `ui._catchterm()`). Any
further writes or flushes will cause further `SIGPIPE`s and furhter
`error.SignalInterrupt`. If we write or flush outside of the
try/except that handle `KeyboardInterrupt` (which
`error.SignalInterrupt` is a subclass of), then control will escape
from the `dispatch` module. Let's fix that by ignoring errors from
flushing the ui.

I would have rather fixed this by restoring the stdout and stderr
streams when the pager dies, but it gets complicated because of
multiple ui instances (ui/lui) and different pager setups between
regular hg and chg.

This changes a test in `test-pager.t`, but I don't understand why. I
would have thought that all the output from the command should have
gone to the broken pager.

Differential Revision: https://phab.mercurial-scm.org/D11627

#!/usr/bin/env python3
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

from __future__ import absolute_import, print_function
import struct
import sys

if len(sys.argv) != 2:
    print('usage: debugcmdserver.py FILE')
    sys.exit(1)

outputfmt = '>cI'
outputfmtsize = struct.calcsize(outputfmt)

if sys.argv[1] == '-':
    log = sys.stderr
else:
    log = open(sys.argv[1], 'a')


def read(size):
    data = sys.stdin.read(size)
    if not data:
        raise EOFError
    sys.stdout.write(data)
    sys.stdout.flush()
    return data


try:
    while True:
        header = read(outputfmtsize)
        channel, length = struct.unpack(outputfmt, header)
        log.write('%s, %-4d' % (channel, length))
        if channel in 'IL':
            log.write(' -> waiting for input\n')
        else:
            data = read(length)
            log.write(' -> %r\n' % data)
        log.flush()
except EOFError:
    pass
finally:
    if log != sys.stderr:
        log.close()