procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
# 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.
Positional arguments construct a log message, which is passed in the `MSG1`
environment variables. 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 %s\n', 'baz', spam='eggs'), a script
configured for the `foo` event can expect an environment with `MSG1=bar baz`,
and `OPT_SPAM=eggs`.
Scripts are configured in the `[logtoprocess]` section, each key an event name.
For example::
[logtoprocess]
commandexception = echo "$MSG1" > /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.
"""
import os
from mercurial.utils import procutil
# 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 = b'ships-with-hg-core'
class processlogger:
"""Map log events to external commands
Arguments are passed on as environment variables.
"""
def __init__(self, ui):
self._scripts = dict(ui.configitems(b'logtoprocess'))
def tracked(self, event):
return bool(self._scripts.get(event))
def log(self, ui, event, msg, opts):
script = self._scripts[event]
maxmsg = 100000
if len(msg) > maxmsg:
# Each env var has a 128KiB limit on linux. msg can be long, in
# particular for command event, where it's the full command line.
# Prefer truncating the message than raising "Argument list too
# long" error.
msg = msg[:maxmsg] + b' (truncated)'
env = {
b'EVENT': event,
b'HGPID': os.getpid(),
b'MSG1': msg,
}
# keyword arguments get prefixed with OPT_ and uppercased
env.update(
(b'OPT_%s' % key.upper(), value) for key, value in opts.items()
)
fullenv = procutil.shellenviron(env)
procutil.runbgcommand(script, fullenv, shell=True)
def uipopulate(ui):
ui.setlogger(b'logtoprocess', processlogger(ui))