Lib/test/test_weakref.py

import sys
import unittest
import weakref

from test_support import run_unittest, verify


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_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
        verify(self.cbcalled == 1,
               "callback did not properly set 'cbcalled'")
        verify(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))

    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")

        # 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")


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):
        dict = weakref.mapping()
        objects = map(Object, range(self.COUNT))
        for o in objects:
            dict[o.arg] = o

        for o in objects:
            self.assert_(weakref.getweakrefcount(o) == 1,
                         "wrong number of weak references to %r!" % o)
            self.assert_(o is dict[o.arg],
                         "wrong object returned by weak dict!")
        items1 = dict.items()
        items2 = dict.copy().items()
        items1.sort()
        items2.sort()
        self.assert_(items1 == items2,
                     "cloning of weak-valued dictionary did not work!")
        del items1, items2
        self.assert_(len(dict) == self.COUNT)
        del objects[0]
        self.assert_(len(dict) == (self.COUNT - 1),
                     "deleting object did not cause dictionary update")
        del objects, o
        self.assert_(len(dict) == 0,
                     "deleting the values did not clear the dictionary")

    def test_weak_keys(self):
        dict = weakref.mapping(weakkeys=1)
        objects = map(Object, range(self.COUNT))
        for o in objects:
            dict[o] = o.arg

        for o in objects:
            self.assert_(weakref.getweakrefcount(o) == 1,
                         "wrong number of weak references to %r!" % o)
            self.assert_(o.arg is dict[o],
                         "wrong object returned by weak dict!")
        items1 = dict.items()
        items2 = dict.copy().items()
        items1.sort()
        items2.sort()
        self.assert_(items1 == items2,
                     "cloning of weak-keyed dictionary did not work!")
        del items1, items2
        self.assert_(len(dict) == self.COUNT)
        del objects[0]
        self.assert_(len(dict) == (self.COUNT - 1),
                     "deleting object did not cause dictionary update")
        del objects, o
        self.assert_(len(dict) == 0,
                     "deleting the keys did not clear the dictionary")


run_unittest(ReferencesTestCase)
run_unittest(MappingTestCase)