test_weakref.py

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import sys
import unittest
import UserList
import weakref

import test_support


class C:
    def method(self):
        pass


class Callable:
    bar = None

    def __call__(self, x):
        self.bar = x


def create_function():
    def f(): pass
    return f

def create_bound_method():
    return C().method

def create_unbound_method():
    return C.method


class TestBase(unittest.TestCase):

    def setUp(self):
        self.cbcalled = 0

    def callback(self, ref):
        self.cbcalled += 1


class ReferencesTestCase(TestBase):

    def test_basic_ref(self):
        self.check_basic_ref(C)
        self.check_basic_ref(create_function)
        self.check_basic_ref(create_bound_method)
        self.check_basic_ref(create_unbound_method)

    def test_basic_callback(self):
        self.check_basic_callback(C)
        self.check_basic_callback(create_function)
        self.check_basic_callback(create_bound_method)
        self.check_basic_callback(create_unbound_method)

    def test_multiple_callbacks(self):
        o = C()
        ref1 = weakref.ref(o, self.callback)
        ref2 = weakref.ref(o, self.callback)
        del o
        self.assert_(ref1() is None,
                     "expected reference to be invalidated")
        self.assert_(ref2() is None,
                     "expected reference to be invalidated")
        self.assert_(self.cbcalled == 2,
                     "callback not called the right number of times")

    def test_multiple_selfref_callbacks(self):
        """Make sure all references are invalidated before callbacks
        are called."""
        #
        # What's important here is that we're using the first
        # reference in the callback invoked on the second reference
        # (the most recently created ref is cleaned up first).  This
        # tests that all references to the object are invalidated
        # before any of the callbacks are invoked, so that we only
        # have one invocation of _weakref.c:cleanup_helper() active
        # for a particular object at a time.
        #
        def callback(object, self=self):
            self.ref()
        c = C()
        self.ref = weakref.ref(c, callback)
        ref1 = weakref.ref(c, callback)
        del c

    def test_proxy_ref(self):
        o = C()
        o.bar = 1
        ref1 = weakref.proxy(o, self.callback)
        ref2 = weakref.proxy(o, self.callback)
        del o

        def check(proxy):
            proxy.bar

        self.assertRaises(weakref.ReferenceError, check, ref1)
        self.assertRaises(weakref.ReferenceError, check, ref2)
        self.assert_(self.cbcalled == 2)

    def check_basic_ref(self, factory):
        o = factory()
        ref = weakref.ref(o)
        self.assert_(ref() is not None,
                     "weak reference to live object should be live")
        o2 = ref()
        self.assert_(o is o2,
                     "<ref>() should return original object if live")

    def check_basic_callback(self, factory):
        self.cbcalled = 0
        o = factory()
        ref = weakref.ref(o, self.callback)
        del o
        self.assert_(self.cbcalled == 1,
                     "callback did not properly set 'cbcalled'")
        self.assert_(ref() is None,
                     "ref2 should be dead after deleting object reference")

    def test_ref_reuse(self):
        o = C()
        ref1 = weakref.ref(o)
        # create a proxy to make sure that there's an intervening creation
        # between these two; it should make no difference
        proxy = weakref.proxy(o)
        ref2 = weakref.ref(o)
        self.assert_(ref1 is ref2,
                     "reference object w/out callback should be re-used")

        o = C()
        proxy = weakref.proxy(o)
        ref1 = weakref.ref(o)
        ref2 = weakref.ref(o)
        self.assert_(ref1 is ref2,
                     "reference object w/out callback should be re-used")
        self.assert_(weakref.getweakrefcount(o) == 2,
                     "wrong weak ref count for object")
        del proxy
        self.assert_(weakref.getweakrefcount(o) == 1,
                     "wrong weak ref count for object after deleting proxy")

    def test_proxy_reuse(self):
        o = C()
        proxy1 = weakref.proxy(o)
        ref = weakref.ref(o)
        proxy2 = weakref.proxy(o)
        self.assert_(proxy1 is proxy2,
                     "proxy object w/out callback should have been re-used")

    def test_basic_proxy(self):
        o = C()
        self.check_proxy(o, weakref.proxy(o))

        L = UserList.UserList()
        p = weakref.proxy(L)
        self.failIf(p, "proxy for empty UserList should be false")
        p.append(12)
        self.assertEqual(len(L), 1)
        self.failUnless(p, "proxy for non-empty UserList should be true")
        p[:] = [2, 3]
        self.assertEqual(len(L), 2)
        self.assertEqual(len(p), 2)
        self.failUnless(3 in p, "proxy didn't support __contains__() properly")
        p[1] = 5
        self.assertEqual(L[1], 5)
        self.assertEqual(p[1], 5)
        L2 = UserList.UserList(L)
        p2 = weakref.proxy(L2)
        self.assertEqual(p, p2)

    def test_callable_proxy(self):
        o = Callable()
        ref1 = weakref.proxy(o)

        self.check_proxy(o, ref1)

        self.assert_(type(ref1) is weakref.CallableProxyType,
                     "proxy is not of callable type")
        ref1('twinkies!')
        self.assert_(o.bar == 'twinkies!',
                     "call through proxy not passed through to original")
        ref1(x='Splat.')
        self.assert_(o.bar == 'Splat.',
                     "call through proxy not passed through to original")

        # expect due to too few args
        self.assertRaises(TypeError, ref1)

        # expect due to too many args
        self.assertRaises(TypeError, ref1, 1, 2, 3)

    def check_proxy(self, o, proxy):
        o.foo = 1
        self.assert_(proxy.foo == 1,
                     "proxy does not reflect attribute addition")
        o.foo = 2
        self.assert_(proxy.foo == 2,
                     "proxy does not reflect attribute modification")
        del o.foo
        self.assert_(not hasattr(proxy, 'foo'),
                     "proxy does not reflect attribute removal")

        proxy.foo = 1
        self.assert_(o.foo == 1,
                     "object does not reflect attribute addition via proxy")
        proxy.foo = 2
        self.assert_(
            o.foo == 2,
            "object does not reflect attribute modification via proxy")
        del proxy.foo
        self.assert_(not hasattr(o, 'foo'),
                     "object does not reflect attribute removal via proxy")

    def test_getweakrefcount(self):
        o = C()
        ref1 = weakref.ref(o)
        ref2 = weakref.ref(o, self.callback)
        self.assert_(weakref.getweakrefcount(o) == 2,
                     "got wrong number of weak reference objects")

        proxy1 = weakref.proxy(o)
        proxy2 = weakref.proxy(o, self.callback)
        self.assert_(weakref.getweakrefcount(o) == 4,
                     "got wrong number of weak reference objects")

    def test_getweakrefs(self):
        o = C()
        ref1 = weakref.ref(o, self.callback)
        ref2 = weakref.ref(o, self.callback)
        del ref1
        self.assert_(weakref.getweakrefs(o) == [ref2],
                     "list of refs does not match")

        o = C()
        ref1 = weakref.ref(o, self.callback)
        ref2 = weakref.ref(o, self.callback)
        del ref2
        self.assert_(weakref.getweakrefs(o) == [ref1],
                     "list of refs does not match")

    def test_newstyle_number_ops(self):
        class F(float):
            pass
        f = F(2.0)
        p = weakref.proxy(f)
        self.assert_(p + 1.0 == 3.0)
        self.assert_(1.0 + p == 3.0)  # this used to SEGV

    def test_callbacks_protected(self):
        """Callbacks protected from already-set exceptions?"""
        # Regression test for SF bug #478534.
        class BogusError(Exception):
            pass
        data = {}
        def remove(k):
            del data[k]
        def encapsulate():
            f = lambda : ()
            data[weakref.ref(f, remove)] = None
            raise BogusError
        try:
            encapsulate()
        except BogusError:
            pass
        else:
            self.fail("exception not properly restored")
        try:
            encapsulate()
        except BogusError:
            pass
        else:
            self.fail("exception not properly restored")


class Object:
    def __init__(self, arg):
        self.arg = arg
    def __repr__(self):
        return "<Object %r>" % self.arg


class MappingTestCase(TestBase):

    COUNT = 10

    def test_weak_values(self):
        #
        #  This exercises d.copy(), d.items(), d[], del d[], len(d).