Mercurial > hg
view tests/test-lock.py @ 33807:b70029f355a3
tests: verify that peer instances only expose interface members
Our abstract interfaces are more useful if we guarantee that
implementations conform to certain rules. Namely, we want to ensure
that objects implementing interfaces don't expose new public
attributes that aren't part of the interface. That way, as long as
consumers don't access "internal" attributes (those beginning with
"_") then (in theory) objects implementing interfaces can be swapped
out and everything will "just work."
We add a test that enforces our "no public attributes not part
of the abstract interface" rule.
We /could/ implement "interface compliance detection" at run-time.
However, that is littered with problems.
The obvious solutions are custom __new__ and __init__ methods.
These rely on derived types actually calling the parent's
implementation, which is no sure bet. Furthermore, __new__ and
__init__ will likely be called before instance-specific attributes
are assigned. In other words, they won't detect public attributes
set on self.__dict__. This means public attribute detection won't
be robust.
We could work around lack of robust self.__dict__ public attribute
detection by having our interfaces implement a custom __getattribute__,
__getattr__, and/or __setattr__. However, this incurs an undesirable
run-time penalty. And, subclasses could override our custom
method, bypassing the check.
The most robust solution is a non-runtime test. So that's what this
commit implements. We have a generic function for validating that an
object only has public attributes defined by abstract classes. Then,
we instantiate some peers and verify a newly constructed object
plays by the rules.
Differential Revision: https://phab.mercurial-scm.org/D339
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 10 Aug 2017 21:00:30 -0700 |
parents | 68c43a416585 |
children | daf12f69699f |
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from __future__ import absolute_import import copy import errno import os import silenttestrunner import tempfile import types import unittest from mercurial import ( error, lock, vfs as vfsmod, ) testlockname = '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.im_func, copy.deepcopy(x.im_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(object): 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): 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=os.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=os.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=os.getcwd())) lock = state.makelock() state.assertacquirecalled(True) # fake a fork forklock = copy.deepcopy(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 testinheritlock(self): d = tempfile.mkdtemp(dir=os.getcwd()) parentstate = teststate(self, d) parentlock = parentstate.makelock() parentstate.assertacquirecalled(True) # set up lock inheritance with parentlock.inherit() as lockname: parentstate.assertreleasecalled(True) parentstate.assertpostreleasecalled(False) parentstate.assertlockexists(True) childstate = teststate(self, d, pidoffset=1) childlock = childstate.makelock(parentlock=lockname) childstate.assertacquirecalled(True) childlock.release() childstate.assertreleasecalled(True) childstate.assertpostreleasecalled(False) childstate.assertlockexists(True) parentstate.resetacquirefn() parentstate.assertacquirecalled(True) parentlock.release() parentstate.assertreleasecalled(True) parentstate.assertpostreleasecalled(True) parentstate.assertlockexists(False) def testmultilock(self): d = tempfile.mkdtemp(dir=os.getcwd()) state0 = teststate(self, d) lock0 = state0.makelock() state0.assertacquirecalled(True) with lock0.inherit() as lock0name: state0.assertreleasecalled(True) state0.assertpostreleasecalled(False) state0.assertlockexists(True) state1 = teststate(self, d, pidoffset=1) lock1 = state1.makelock(parentlock=lock0name) state1.assertacquirecalled(True) # from within lock1, acquire another lock with lock1.inherit() as lock1name: # since the file on disk is lock0's this should have the same # name self.assertEqual(lock0name, lock1name) state2 = teststate(self, d, pidoffset=2) lock2 = state2.makelock(parentlock=lock1name) state2.assertacquirecalled(True) lock2.release() state2.assertreleasecalled(True) state2.assertpostreleasecalled(False) state2.assertlockexists(True) state1.resetacquirefn() state1.assertacquirecalled(True) lock1.release() state1.assertreleasecalled(True) state1.assertpostreleasecalled(False) state1.assertlockexists(True) lock0.release() def testinheritlockfork(self): d = tempfile.mkdtemp(dir=os.getcwd()) parentstate = teststate(self, d) parentlock = parentstate.makelock() parentstate.assertacquirecalled(True) # set up lock inheritance with parentlock.inherit() as lockname: childstate = teststate(self, d, pidoffset=1) childlock = childstate.makelock(parentlock=lockname) childstate.assertacquirecalled(True) # fork the child lock forkchildlock = copy.deepcopy(childlock) forkchildlock._pidoffset += 1 forkchildlock.release() childstate.assertreleasecalled(False) childstate.assertpostreleasecalled(False) childstate.assertlockexists(True) # release the child lock childlock.release() childstate.assertreleasecalled(True) childstate.assertpostreleasecalled(False) childstate.assertlockexists(True) parentlock.release() def testinheritcheck(self): d = tempfile.mkdtemp(dir=os.getcwd()) state = teststate(self, d) def check(): raise error.LockInheritanceContractViolation('check failed') lock = state.makelock(inheritchecker=check) state.assertacquirecalled(True) with self.assertRaises(error.LockInheritanceContractViolation): with lock.inherit(): pass lock.release() 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=os.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 == "") state.assertlockexists(False) if __name__ == '__main__': silenttestrunner.main(__name__)