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.
# dirstateguard.py - class to allow restoring dirstate after failure
#
# Copyright 2005-2007 Olivia Mackall <olivia@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import os
from .i18n import _
from . import (
error,
narrowspec,
requirements,
util,
)
class dirstateguard(util.transactional):
"""Restore dirstate at unexpected failure.
At the construction, this class does:
- write current ``repo.dirstate`` out, and
- save ``.hg/dirstate`` into the backup file
This restores ``.hg/dirstate`` from backup file, if ``release()``
is invoked before ``close()``.
This just removes the backup file at ``close()`` before ``release()``.
"""
def __init__(self, repo, name):
self._repo = repo
self._active = False
self._closed = False
def getname(prefix):
fd, fname = repo.vfs.mkstemp(prefix=prefix)
os.close(fd)
return fname
self._backupname = getname(b'dirstate.backup.%s.' % name)
repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
# Don't make this the empty string, things may join it with stuff and
# blindly try to unlink it, which could be bad.
self._narrowspecbackupname = None
if requirements.NARROW_REQUIREMENT in repo.requirements:
self._narrowspecbackupname = getname(
b'narrowspec.backup.%s.' % name
)
narrowspec.savewcbackup(repo, self._narrowspecbackupname)
self._active = True
def __del__(self):
if self._active: # still active
# this may occur, even if this class is used correctly:
# for example, releasing other resources like transaction
# may raise exception before ``dirstateguard.release`` in
# ``release(tr, ....)``.
self._abort()
def close(self):
if not self._active: # already inactivated
msg = (
_(b"can't close already inactivated backup: %s")
% self._backupname
)
raise error.Abort(msg)
self._repo.dirstate.clearbackup(
self._repo.currenttransaction(), self._backupname
)
if self._narrowspecbackupname:
narrowspec.clearwcbackup(self._repo, self._narrowspecbackupname)
self._active = False
self._closed = True
def _abort(self):
if self._narrowspecbackupname:
narrowspec.restorewcbackup(self._repo, self._narrowspecbackupname)
self._repo.dirstate.restorebackup(
self._repo.currenttransaction(), self._backupname
)
self._active = False
def release(self):
if not self._closed:
if not self._active: # already inactivated
msg = (
_(b"can't release already inactivated backup: %s")
% self._backupname
)
raise error.Abort(msg)
self._abort()