view hgdemandimport/tracing.py @ 47379:f6bb181c75f8

rust: Parse "subinclude"d files along the way, not later

When parsing a `.hgignore` file and encountering an `include:` line,
the included file is parsed recursively right then in a depth-first fashion.

With `subinclude:` however included files were parsed (recursively) much later.
This changes it to be expanded during parsing, like `.hgignore`.

The motivation for this is an upcoming changeset that needs to detect changes
in which files are ignored or not. The plan is to hash all ignore files while
they are being read, and store that hash in the dirstate (in v2 format).
In order to allow a potential alternative implementations to read that format,
the algorithm to compute that hash must be documented. Having a well-defined
depth-first ordering for the tree of (sub-)included files makes that easier.

Differential Revision: https://phab.mercurial-scm.org/D10834

# 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
_session = 'none'


def _isactive():
    global _pipe, _session, _checked
    if _pipe is None:
        if _checked:
            return False
        _checked = True
        if 'HGCATAPULTSERVERPIPE' not in os.environ:
            return False
        _pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
        _session = os.environ.get('HGCATAPULTSESSION', 'none')
    return True


@contextlib.contextmanager
def log(whencefmt, *whenceargs):
    if not _isactive():
        yield
        return
    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


def counter(label, amount, *labelargs):
    if not _isactive():
        return
    l = label % labelargs
    # See above in log() for why this is in a try/except.
    try:
        _pipe.write('COUNTER %s %d %s\n' % (_session, amount, l))
    except IOError:
        pass