view hgdemandimport/tracing.py @ 39275:b17d27ea61fb

phase: use `_phase` revset instead of string interpolation

The previous code was hackyer and assume all phases had an associated revset.
The later might no longer be true once we introduce more internal phase.

# Support code for event tracing in Mercurial. Lives in demandimport
# so it can also be used in demandimport.
#
# Copyright 2018 Google LLC.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import

import contextlib
import os

_pipe = None
_checked = False

@contextlib.contextmanager
def log(whencefmt, *whenceargs):
    global _pipe, _session, _checked
    if _pipe is None:
        if _checked:
            yield
            return
        _checked = True
        if 'HGCATAPULTSERVERPIPE' not in os.environ:
            yield
            return
        _pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
        _session = os.environ.get('HGCATAPULTSESSION', 'none')
    whence = whencefmt % whenceargs
    try:
        _pipe.write('START %s %s\n' % (_session, whence))
        yield
    finally:
        _pipe.write('END %s %s\n' % (_session, whence))