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.
# state.py - fsmonitor persistent state
#
# Copyright 2013-2016 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.
import errno
import os
import socket
import struct
from mercurial.i18n import _
from mercurial import (
encoding,
pathutil,
util,
)
_version = 4
_versionformat = b">I"
class state:
def __init__(self, repo):
self._vfs = repo.vfs
self._ui = repo.ui
self._rootdir = pathutil.normasprefix(repo.root)
self._lastclock = None
self._identity = util.filestat(None)
self.mode = self._ui.config(b'fsmonitor', b'mode')
self.walk_on_invalidate = self._ui.configbool(
b'fsmonitor', b'walk_on_invalidate'
)
self.timeout = float(self._ui.config(b'fsmonitor', b'timeout'))
def get(self):
try:
file = self._vfs(b'fsmonitor.state', b'rb')
except IOError as inst:
self._identity = util.filestat(None)
if inst.errno != errno.ENOENT:
raise
return None, None, None
self._identity = util.filestat.fromfp(file)
versionbytes = file.read(4)
if len(versionbytes) < 4:
self._ui.log(
b'fsmonitor',
b'fsmonitor: state file only has %d bytes, '
b'nuking state\n' % len(versionbytes),
)
self.invalidate()
return None, None, None
try:
diskversion = struct.unpack(_versionformat, versionbytes)[0]
if diskversion != _version:
# different version, nuke state and start over
self._ui.log(
b'fsmonitor',
b'fsmonitor: version switch from %d to '
b'%d, nuking state\n' % (diskversion, _version),
)
self.invalidate()
return None, None, None
state = file.read().split(b'\0')
# state = hostname\0clock\0ignorehash\0 + list of files, each
# followed by a \0
if len(state) < 3:
self._ui.log(
b'fsmonitor',
b'fsmonitor: state file truncated (expected '
b'3 chunks, found %d), nuking state\n',
len(state),
)
self.invalidate()
return None, None, None
diskhostname = state[0]
hostname = encoding.strtolocal(socket.gethostname())
if diskhostname != hostname:
# file got moved to a different host
self._ui.log(
b'fsmonitor',
b'fsmonitor: stored hostname "%s" '
b'different from current "%s", nuking state\n'
% (diskhostname, hostname),
)
self.invalidate()
return None, None, None
clock = state[1]
ignorehash = state[2]
# discard the value after the last \0
notefiles = state[3:-1]
finally:
file.close()
return clock, ignorehash, notefiles
def set(self, clock, ignorehash, notefiles):
if clock is None:
self.invalidate()
return
# Read the identity from the file on disk rather than from the open file
# pointer below, because the latter is actually a brand new file.
identity = util.filestat.frompath(self._vfs.join(b'fsmonitor.state'))
if identity != self._identity:
self._ui.debug(
b'skip updating fsmonitor.state: identity mismatch\n'
)
return
try:
file = self._vfs(
b'fsmonitor.state', b'wb', atomictemp=True, checkambig=True
)
except (IOError, OSError):
self._ui.warn(_(b"warning: unable to write out fsmonitor state\n"))
return
with file:
file.write(struct.pack(_versionformat, _version))
file.write(encoding.strtolocal(socket.gethostname()) + b'\0')
file.write(clock + b'\0')
file.write(ignorehash + b'\0')
if notefiles:
file.write(b'\0'.join(notefiles))
file.write(b'\0')
def invalidate(self):
try:
os.unlink(os.path.join(self._rootdir, b'.hg', b'fsmonitor.state'))
except FileNotFoundError:
pass
self._identity = util.filestat(None)
def setlastclock(self, clock):
self._lastclock = clock
def getlastclock(self):
return self._lastclock