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.
import copy
import errno
import tempfile
import types
import unittest
import silenttestrunner
from mercurial import (
encoding,
error,
lock,
vfs as vfsmod,
)
testlockname = b'testlock'
# work around http://bugs.python.org/issue1515
if types.MethodType not in copy._deepcopy_dispatch:
def _deepcopy_method(x, memo):
return type(x)(x.__func__, copy.deepcopy(x.__self__, memo), x.im_class)
copy._deepcopy_dispatch[types.MethodType] = _deepcopy_method
class lockwrapper(lock.lock):
def __init__(self, pidoffset, *args, **kwargs):
# lock.lock.__init__() calls lock(), so the pidoffset assignment needs
# to be earlier
self._pidoffset = pidoffset
super(lockwrapper, self).__init__(*args, **kwargs)
def _getpid(self):
return super(lockwrapper, self)._getpid() + self._pidoffset
class teststate:
def __init__(self, testcase, dir, pidoffset=0):
self._testcase = testcase
self._acquirecalled = False
self._releasecalled = False
self._postreleasecalled = False
self.vfs = vfsmod.vfs(dir, audit=False)
self._pidoffset = pidoffset
def makelock(self, *args, **kwargs):
l = lockwrapper(
self._pidoffset,
self.vfs,
testlockname,
releasefn=self.releasefn,
acquirefn=self.acquirefn,
*args,
**kwargs
)
l.postrelease.append(self.postreleasefn)
return l
def acquirefn(self):
self._acquirecalled = True
def releasefn(self):
self._releasecalled = True
def postreleasefn(self, success):
self._postreleasecalled = True
def assertacquirecalled(self, called):
self._testcase.assertEqual(
self._acquirecalled,
called,
'expected acquire to be %s but was actually %s'
% (
self._tocalled(called),
self._tocalled(self._acquirecalled),
),
)
def resetacquirefn(self):
self._acquirecalled = False
def assertreleasecalled(self, called):
self._testcase.assertEqual(
self._releasecalled,
called,
'expected release to be %s but was actually %s'
% (
self._tocalled(called),
self._tocalled(self._releasecalled),
),
)
def assertpostreleasecalled(self, called):
self._testcase.assertEqual(
self._postreleasecalled,
called,
'expected postrelease to be %s but was actually %s'
% (
self._tocalled(called),
self._tocalled(self._postreleasecalled),
),
)
def assertlockexists(self, exists):
actual = self.vfs.lexists(testlockname)
self._testcase.assertEqual(
actual,
exists,
'expected lock to %s but actually did %s'
% (
self._toexists(exists),
self._toexists(actual),
),
)
def _tocalled(self, called):
if called:
return 'called'
else:
return 'not called'
def _toexists(self, exists):
if exists:
return 'exist'
else:
return 'not exist'
class testlock(unittest.TestCase):
def testlock(self):
state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
lock = state.makelock()
state.assertacquirecalled(True)
lock.release()
state.assertreleasecalled(True)
state.assertpostreleasecalled(True)
state.assertlockexists(False)
def testrecursivelock(self):
state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
lock = state.makelock()
state.assertacquirecalled(True)
state.resetacquirefn()
lock.lock()
# recursive lock should not call acquirefn again
state.assertacquirecalled(False)
lock.release() # brings lock refcount down from 2 to 1
state.assertreleasecalled(False)
state.assertpostreleasecalled(False)
state.assertlockexists(True)
lock.release() # releases the lock
state.assertreleasecalled(True)
state.assertpostreleasecalled(True)
state.assertlockexists(False)
def testlockfork(self):
state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
lock = state.makelock()
state.assertacquirecalled(True)
# fake a fork
forklock = copy.copy(lock)
forklock._pidoffset = 1
forklock.release()
state.assertreleasecalled(False)
state.assertpostreleasecalled(False)
state.assertlockexists(True)
# release the actual lock
lock.release()
state.assertreleasecalled(True)
state.assertpostreleasecalled(True)
state.assertlockexists(False)
def testfrequentlockunlock(self):
"""This tests whether lock acquisition fails as expected, even if
(1) lock can't be acquired (makelock fails by EEXIST), and
(2) locker info can't be read in (readlock fails by ENOENT) while
retrying 5 times.
"""
d = tempfile.mkdtemp(dir=encoding.getcwd())
state = teststate(self, d)
def emulatefrequentlock(*args):
raise OSError(errno.EEXIST, "File exists")
def emulatefrequentunlock(*args):
raise OSError(errno.ENOENT, "No such file or directory")
state.vfs.makelock = emulatefrequentlock
state.vfs.readlock = emulatefrequentunlock
try:
state.makelock(timeout=0)
self.fail("unexpected lock acquisition")
except error.LockHeld as why:
self.assertTrue(why.errno == errno.ETIMEDOUT)
self.assertTrue(why.locker == b"")
state.assertlockexists(False)
if __name__ == '__main__':
silenttestrunner.main(__name__)