hgext/logtoprocess.py

strip: don't allow empty changegroup in bundle1

Applying an empty changegroup has been an error since the
beginning. The only exception was strip, which would allow to apply an
empty changegroup from the temporary bundle. However, the emptyok=True
option was only set for bundle1 bundles. In other words, temporary
bundle2 bundles would fail if they were empty.

Bundle2 has now been used enough that it seems safe to say that we
simply don't create bundle2 bundles with empty changegroups. That also
suggests that we never create bundle1 bundles with empty changegroups
(i.e. empty bundle1 bundles, since bundle1 is just a changegroup),
because, AFAICT, the code leading up to the application of the bundle
is the same for bundle1 and bundle2.

Therefore, let's stop passing emptyok=True, so we more clearly get the
same behavior for bundle1 and bundle2.

# logtoprocess.py - send ui.log() data to a subprocess
#
# Copyright 2016 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""send ui.log() data to a subprocess (EXPERIMENTAL)

This extension lets you specify a shell command per ui.log() event,
sending all remaining arguments to as environment variables to that command.

Each positional argument to the method results in a `MSG[N]` key in the
environment, starting at 1 (so `MSG1`, `MSG2`, etc.). Each keyword argument
is set as a `OPT_UPPERCASE_KEY` variable (so the key is uppercased, and
prefixed with `OPT_`). The original event name is passed in the `EVENT`
environment variable, and the process ID of mercurial is given in `HGPID`.

So given a call `ui.log('foo', 'bar', 'baz', spam='eggs'), a script configured
for the `foo` event can expect an environment with `MSG1=bar`, `MSG2=baz`, and
`OPT_SPAM=eggs`.

Scripts are configured in the `[logtoprocess]` section, each key an event name.
For example::

  [logtoprocess]
  commandexception = echo "$MSG2$MSG3" > /var/log/mercurial_exceptions.log

would log the warning message and traceback of any failed command dispatch.

Scripts are run asynchronously as detached daemon processes; mercurial will
not ensure that they exit cleanly.

"""

from __future__ import absolute_import

import itertools
import os
import platform
import subprocess
import sys

from mercurial import encoding

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'

def uisetup(ui):
    if platform.system() == 'Windows':
        # no fork on Windows, but we can create a detached process
        # https://msdn.microsoft.com/en-us/library/windows/desktop/ms684863.aspx
        # No stdlib constant exists for this value
        DETACHED_PROCESS = 0x00000008
        _creationflags = DETACHED_PROCESS | subprocess.CREATE_NEW_PROCESS_GROUP

        def runshellcommand(script, env):
            # we can't use close_fds *and* redirect stdin. I'm not sure that we
            # need to because the detached process has no console connection.
            subprocess.Popen(
                script, shell=True, env=env, close_fds=True,
                creationflags=_creationflags)
    else:
        def runshellcommand(script, env):
            # double-fork to completely detach from the parent process
            # based on http://code.activestate.com/recipes/278731
            pid = os.fork()
            if pid:
                # parent
                return
            # subprocess.Popen() forks again, all we need to add is
            # flag the new process as a new session.
            if sys.version_info < (3, 2):
                newsession = {'preexec_fn': os.setsid}
            else:
                newsession = {'start_new_session': True}
            try:
                # connect stdin to devnull to make sure the subprocess can't
                # muck up that stream for mercurial.
                subprocess.Popen(
                    script, shell=True, stdin=open(os.devnull, 'r'), env=env,
                    close_fds=True, **newsession)
            finally:
                # mission accomplished, this child needs to exit and not
                # continue the hg process here.
                os._exit(0)

    class logtoprocessui(ui.__class__):
        def log(self, event, *msg, **opts):
            """Map log events to external commands

            Arguments are passed on as environment variables.

            """
            script = self.config('logtoprocess', event)
            if script:
                if msg:
                    # try to format the log message given the remaining
                    # arguments
                    try:
                        # Python string formatting with % either uses a
                        # dictionary *or* tuple, but not both. If we have
                        # keyword options, assume we need a mapping.
                        formatted = msg[0] % (opts or msg[1:])
                    except (TypeError, KeyError):
                        # Failed to apply the arguments, ignore
                        formatted = msg[0]
                    messages = (formatted,) + msg[1:]
                else:
                    messages = msg
                # positional arguments are listed as MSG[N] keys in the
                # environment
                msgpairs = (
                    ('MSG{0:d}'.format(i), str(m))
                    for i, m in enumerate(messages, 1))
                # keyword arguments get prefixed with OPT_ and uppercased
                optpairs = (
                    ('OPT_{0}'.format(key.upper()), str(value))
                    for key, value in opts.iteritems())
                env = dict(itertools.chain(encoding.environ.items(),
                                           msgpairs, optpairs),
                           EVENT=event, HGPID=str(os.getpid()))
                # Connect stdin to /dev/null to prevent child processes messing
                # with mercurial's stdin.
                runshellcommand(script, env)
            return super(logtoprocessui, self).log(event, *msg, **opts)

    # Replace the class for this instance and all clones created from it:
    ui.__class__ = logtoprocessui