view hgdemandimport/tracing.py @ 42047:715d3220ac4f

wix: add a hook for a prebuild script to inject extra libraries

I need this to build packages for Google so we can bundle some
extensions in the installed image. My assumption is that this is most
interesting for the .msi images so I only wired it up there. I'm not
thrilled with the interface this provides, but it was an easy way to
retain debug messages on Windows while also having enough structure to
know what lines are actually module names for py2exe.

Still pending on my end: I need to bundle a couple of config files,
and at least one data file. I'm open to advice on how to do those
things, and how to do this better.

Differential Revision: https://phab.mercurial-scm.org/D6164

# 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:
        # Both writes to the pipe are wrapped in try/except to ignore
        # errors, as we can see mysterious errors in here if the pager
        # is active. Presumably other conditions could trigger
        # problems too.
        try:
            _pipe.write('START %s %s\n' % (_session, whence))
        except IOError:
            pass
        yield
    finally:
        try:
            _pipe.write('END %s %s\n' % (_session, whence))
        except IOError:
            pass