summaryrefslogtreecommitdiffstats
path: root/Lib/test/test_weakref.py
blob: 74b9a878521d95683147e705a63af9ca1be8e1a6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
import gc
import sys
import unittest
import collections
import weakref
import operator
import contextlib
import copy

from test import support

# Used in ReferencesTestCase.test_ref_created_during_del() .
ref_from_del = None

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


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)

        # Just make sure the tp_repr handler doesn't raise an exception.
        # Live reference:
        o = C()
        wr = weakref.ref(o)
        repr(wr)
        # Dead reference:
        del o
        repr(wr)

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

    def test_multiple_callbacks(self):
        o = C()
        ref1 = weakref.ref(o, self.callback)
        ref2 = weakref.ref(o, self.callback)
        del o
        self.assertTrue(ref1() is None,
                     "expected reference to be invalidated")
        self.assertTrue(ref2() is None,
                     "expected reference to be invalidated")
        self.assertTrue(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(ReferenceError, check, ref1)
        self.assertRaises(ReferenceError, check, ref2)
        self.assertRaises(ReferenceError, bool, weakref.proxy(C()))
        self.assertEqual(self.cbcalled, 2)

    def check_basic_ref(self, factory):
        o = factory()
        ref = weakref.ref(o)
        self.assertTrue(ref() is not None,
                     "weak reference to live object should be live")
        o2 = ref()
        self.assertTrue(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.assertTrue(self.cbcalled == 1,
                     "callback did not properly set 'cbcalled'")
        self.assertTrue(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.assertTrue(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.assertTrue(ref1 is ref2,
                     "reference object w/out callback should be re-used")
        self.assertTrue(weakref.getweakrefcount(o) == 2,
                     "wrong weak ref count for object")
        del proxy
        self.assertTrue(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.assertTrue(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 = collections.UserList()
        p = weakref.proxy(L)
        self.assertFalse(p, "proxy for empty UserList should be false")
        p.append(12)
        self.assertEqual(len(L), 1)
        self.assertTrue(p, "proxy for non-empty UserList should be true")
        p[:] = [2, 3]
        self.assertEqual(len(L), 2)
        self.assertEqual(len(p), 2)
        self.assertIn(3, p, "proxy didn't support __contains__() properly")
        p[1] = 5
        self.assertEqual(L[1], 5)
        self.assertEqual(p[1], 5)
        L2 = collections.UserList(L)
        p2 = weakref.proxy(L2)
        self.assertEqual(p, p2)
        ## self.assertEqual(repr(L2), repr(p2))
        L3 = collections.UserList(range(10))
        p3 = weakref.proxy(L3)
        self.assertEqual(L3[:], p3[:])
        self.assertEqual(L3[5:], p3[5:])
        self.assertEqual(L3[:5], p3[:5])
        self.assertEqual(L3[2:5], p3[2:5])

    def test_proxy_unicode(self):
        # See bug 5037
        class C(object):
            def __str__(self):
                return "string"
            def __bytes__(self):
                return b"bytes"
        instance = C()
        self.assertIn("__bytes__", dir(weakref.proxy(instance)))
        self.assertEqual(bytes(weakref.proxy(instance)), b"bytes")

    def test_proxy_index(self):
        class C:
            def __index__(self):
                return 10
        o = C()
        p = weakref.proxy(o)
        self.assertEqual(operator.index(p), 10)

    def test_proxy_div(self):
        class C:
            def __floordiv__(self, other):
                return 42
            def __ifloordiv__(self, other):
                return 21
        o = C()
        p = weakref.proxy(o)
        self.assertEqual(p // 5, 42)
        p //= 5
        self.assertEqual(p, 21)

    # The PyWeakref_* C API is documented as allowing either NULL or
    # None as the value for the callback, where either means "no
    # callback".  The "no callback" ref and proxy objects are supposed
    # to be shared so long as they exist by all callers so long as
    # they are active.  In Python 2.3.3 and earlier, this guarantee
    # was not honored, and was broken in different ways for
    # PyWeakref_NewRef() and PyWeakref_NewProxy().  (Two tests.)

    def test_shared_ref_without_callback(self):
        self.check_shared_without_callback(weakref.ref)

    def test_shared_proxy_without_callback(self):
        self.check_shared_without_callback(weakref.proxy)

    def check_shared_without_callback(self, makeref):
        o = Object(1)
        p1 = makeref(o, None)
        p2 = makeref(o, None)
        self.assertTrue(p1 is p2, "both callbacks were None in the C API")
        del p1, p2
        p1 = makeref(o)
        p2 = makeref(o, None)
        self.assertTrue(p1 is p2, "callbacks were NULL, None in the C API")
        del p1, p2
        p1 = makeref(o)
        p2 = makeref(o)
        self.assertTrue(p1 is p2, "both callbacks were NULL in the C API")
        del p1, p2
        p1 = makeref(o, None)
        p2 = makeref(o)
        self.assertTrue(p1 is p2, "callbacks were None, NULL in the C API")

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

        self.check_proxy(o, ref1)

        self.assertTrue(type(ref1) is weakref.CallableProxyType,
                     "proxy is not of callable type")
        ref1('twinkies!')
        self.assertTrue(o.bar == 'twinkies!',
                     "call through proxy not passed through to original")
        ref1(x='Splat.')
        self.assertTrue(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.assertTrue(proxy.foo == 1,
                     "proxy does not reflect attribute addition")
        o.foo = 2
        self.assertTrue(proxy.foo == 2,
                     "proxy does not reflect attribute modification")
        del o.foo
        self.assertTrue(not hasattr(proxy, 'foo'),
                     "proxy does not reflect attribute removal")

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

    def test_proxy_deletion(self):
        # Test clearing of SF bug #762891
        class Foo:
            result = None
            def __delitem__(self, accessor):
                self.result = accessor
        g = Foo()
        f = weakref.proxy(g)
        del f[0]
        self.assertEqual(f.result, 0)

    def test_proxy_bool(self):
        # Test clearing of SF bug #1170766
        class List(list): pass
        lyst = List()
        self.assertEqual(bool(weakref.proxy(lyst)), bool(lyst))

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

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

        del ref1, ref2, proxy1, proxy2
        self.assertTrue(weakref.getweakrefcount(o) == 0,
                     "weak reference objects not unlinked from"
                     " referent when discarded.")

        # assumes ints do not support weakrefs
        self.assertTrue(weakref.getweakrefcount(1) == 0,
                     "got wrong number of weak reference objects for int")

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

        del ref1
        self.assertTrue(weakref.getweakrefs(o) == [],
                     "list of refs not cleared")

        # assumes ints do not support weakrefs
        self.assertTrue(weakref.getweakrefs(1) == [],
                     "list of refs does not match for int")

    def test_newstyle_number_ops(self):
        class F(float):
            pass
        f = F(2.0)
        p = weakref.proxy(f)
        self.assertTrue(p + 1.0 == 3.0)
        self.assertTrue(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")

    def test_sf_bug_840829(self):
        # "weakref callbacks and gc corrupt memory"
        # subtype_dealloc erroneously exposed a new-style instance
        # already in the process of getting deallocated to gc,
        # causing double-deallocation if the instance had a weakref
        # callback that triggered gc.
        # If the bug exists, there probably won't be an obvious symptom
        # in a release build.  In a debug build, a segfault will occur
        # when the second attempt to remove the instance from the "list
        # of all objects" occurs.

        import gc

        class C(object):
            pass

        c = C()
        wr = weakref.ref(c, lambda ignore: gc.collect())
        del c

        # There endeth the first part.  It gets worse.
        del wr

        c1 = C()
        c1.i = C()
        wr = weakref.ref(c1.i, lambda ignore: gc.collect())

        c2 = C()
        c2.c1 = c1
        del c1  # still alive because c2 points to it

        # Now when subtype_dealloc gets called on c2, it's not enough just
        # that c2 is immune from gc while the weakref callbacks associated
        # with c2 execute (there are none in this 2nd half of the test, btw).
        # subtype_dealloc goes on to call the base classes' deallocs too,
        # so any gc triggered by weakref callbacks associated with anything
        # torn down by a base class dealloc can also trigger double
        # deallocation of c2.
        del c2

    def test_callback_in_cycle_1(self):
        import gc

        class J(object):
            pass

        class II(object):
            def acallback(self, ignore):
                self.J

        I = II()
        I.J = J
        I.wr = weakref.ref(J, I.acallback)

        # Now J and II are each in a self-cycle (as all new-style class
        # objects are, since their __mro__ points back to them).  I holds
        # both a weak reference (I.wr) and a strong reference (I.J) to class
        # J.  I is also in a cycle (I.wr points to a weakref that references
        # I.acallback).  When we del these three, they all become trash, but
        # the cycles prevent any of them from getting cleaned up immediately.
        # Instead they have to wait for cyclic gc to deduce that they're
        # trash.
        #
        # gc used to call tp_clear on all of them, and the order in which
        # it does that is pretty accidental.  The exact order in which we
        # built up these things manages to provoke gc into running tp_clear
        # in just the right order (I last).  Calling tp_clear on II leaves
        # behind an insane class object (its __mro__ becomes NULL).  Calling
        # tp_clear on J breaks its self-cycle, but J doesn't get deleted
        # just then because of the strong reference from I.J.  Calling
        # tp_clear on I starts to clear I's __dict__, and just happens to
        # clear I.J first -- I.wr is still intact.  That removes the last
        # reference to J, which triggers the weakref callback.  The callback
        # tries to do "self.J", and instances of new-style classes look up
        # attributes ("J") in the class dict first.  The class (II) wants to
        # search II.__mro__, but that's NULL.   The result was a segfault in
        # a release build, and an assert failure in a debug build.
        del I, J, II
        gc.collect()

    def test_callback_in_cycle_2(self):
        import gc

        # This is just like test_callback_in_cycle_1, except that II is an
        # old-style class.  The symptom is different then:  an instance of an
        # old-style class looks in its own __dict__ first.  'J' happens to
        # get cleared from I.__dict__ before 'wr', and 'J' was never in II's
        # __dict__, so the attribute isn't found.  The difference is that
        # the old-style II doesn't have a NULL __mro__ (it doesn't have any
        # __mro__), so no segfault occurs.  Instead it got:
        #    test_callback_in_cycle_2 (__main__.ReferencesTestCase) ...
        #    Exception exceptions.AttributeError:
        #   "II instance has no attribute 'J'" in <bound method II.acallback
        #       of <?.II instance at 0x00B9B4B8>> ignored

        class J(object):
            pass

        class II:
            def acallback(self, ignore):
                self.J

        I = II()
        I.J = J
        I.wr = weakref.ref(J, I.acallback)

        del I, J, II
        gc.collect()

    def test_callback_in_cycle_3(self):
        import gc

        # This one broke the first patch that fixed the last two.  In this
        # case, the objects reachable from the callback aren't also reachable
        # from the object (c1) *triggering* the callback:  you can get to
        # c1 from c2, but not vice-versa.  The result was that c2's __dict__
        # got tp_clear'ed by the time the c2.cb callback got invoked.

        class C:
            def cb(self, ignore):
                self.me
                self.c1
                self.wr

        c1, c2 = C(), C()

        c2.me = c2
        c2.c1 = c1
        c2.wr = weakref.ref(c1, c2.cb)

        del c1, c2
        gc.collect()

    def test_callback_in_cycle_4(self):
        import gc

        # Like test_callback_in_cycle_3, except c2 and c1 have different
        # classes.  c2's class (C) isn't reachable from c1 then, so protecting
        # objects reachable from the dying object (c1) isn't enough to stop
        # c2's class (C) from getting tp_clear'ed before c2.cb is invoked.
        # The result was a segfault (C.__mro__ was NULL when the callback
        # tried to look up self.me).

        class C(object):
            def cb(self, ignore):
                self.me
                self.c1
                self.wr

        class D:
            pass

        c1, c2 = D(), C()

        c2.me = c2
        c2.c1 = c1
        c2.wr = weakref.ref(c1, c2.cb)

        del c1, c2, C, D
        gc.collect()

    def test_callback_in_cycle_resurrection(self):
        import gc

        # Do something nasty in a weakref callback:  resurrect objects
        # from dead cycles.  For this to be attempted, the weakref and
        # its callback must also be part of the cyclic trash (else the
        # objects reachable via the callback couldn't be in cyclic trash
        # to begin with -- the callback would act like an external root).
        # But gc clears trash weakrefs with callbacks early now, which
        # disables the callbacks, so the callbacks shouldn't get called
        # at all (and so nothing actually gets resurrected).

        alist = []
        class C(object):
            def __init__(self, value):
                self.attribute = value

            def acallback(self, ignore):
                alist.append(self.c)

        c1, c2 = C(1), C(2)
        c1.c = c2
        c2.c = c1
        c1.wr = weakref.ref(c2, c1.acallback)
        c2.wr = weakref.ref(c1, c2.acallback)

        def C_went_away(ignore):
            alist.append("C went away")
        wr = weakref.ref(C, C_went_away)

        del c1, c2, C   # make them all trash
        self.assertEqual(alist, [])  # del isn't enough to reclaim anything

        gc.collect()
        # c1.wr and c2.wr were part of the cyclic trash, so should have
        # been cleared without their callbacks executing.  OTOH, the weakref
        # to C is bound to a function local (wr), and wasn't trash, so that
        # callback should have been invoked when C went away.
        self.assertEqual(alist, ["C went away"])
        # The remaining weakref should be dead now (its callback ran).
        self.assertEqual(wr(), None)

        del alist[:]
        gc.collect()
        self.assertEqual(alist, [])

    def test_callbacks_on_callback(self):
        import gc

        # Set up weakref callbacks *on* weakref callbacks.
        alist = []
        def safe_callback(ignore):
            alist.append("safe_callback called")

        class C(object):
            def cb(self, ignore):
                alist.append("cb called")

        c, d = C(), C()
        c.other = d
        d.other = c
        callback = c.cb
        c.wr = weakref.ref(d, callback)     # this won't trigger
        d.wr = weakref.ref(callback, d.cb)  # ditto
        external_wr = weakref.ref(callback, safe_callback)  # but this will
        self.assertTrue(external_wr() is callback)

        # The weakrefs attached to c and d should get cleared, so that
        # C.cb is never called.  But external_wr isn't part of the cyclic
        # trash, and no cyclic trash is reachable from it, so safe_callback
        # should get invoked when the bound method object callback (c.cb)
        # -- which is itself a callback, and also part of the cyclic trash --
        # gets reclaimed at the end of gc.

        del callback, c, d, C
        self.assertEqual(alist, [])  # del isn't enough to clean up cycles
        gc.collect()
        self.assertEqual(alist, ["safe_callback called"])
        self.assertEqual(external_wr(), None)

        del alist[:]
        gc.collect()
        self.assertEqual(alist, [])

    def test_gc_during_ref_creation(self):
        self.check_gc_during_creation(weakref.ref)

    def test_gc_during_proxy_creation(self):
        self.check_gc_during_creation(weakref.proxy)

    def check_gc_during_creation(self, makeref):
        thresholds = gc.get_threshold()
        gc.set_threshold(1, 1, 1)
        gc.collect()
        class A:
            pass

        def callback(*args):
            pass

        referenced = A()

        a = A()
        a.a = a
        a.wr = makeref(referenced)

        try:
            # now make sure the object and the ref get labeled as
            # cyclic trash:
            a = A()
            weakref.ref(referenced, callback)

        finally:
            gc.set_threshold(*thresholds)

    def test_ref_created_during_del(self):
        # Bug #1377858
        # A weakref created in an object's __del__() would crash the
        # interpreter when the weakref was cleaned up since it would refer to
        # non-existent memory.  This test should not segfault the interpreter.
        class Target(object):
            def __del__(self):
                global ref_from_del
                ref_from_del = weakref.ref(self)

        w = Target()

    def test_init(self):
        # Issue 3634
        # <weakref to class>.__init__() doesn't check errors correctly
        r = weakref.ref(Exception)
        self.assertRaises(TypeError, r.__init__, 0, 0, 0, 0, 0)
        # No exception should be raised here
        gc.collect()

    def test_classes(self):
        # Check that classes are weakrefable.
        class A(object):
            pass
        l = []
        weakref.ref(int)
        a = weakref.ref(A, l.append)
        A = None
        gc.collect()
        self.assertEqual(a(), None)
        self.assertEqual(l, [a])


class SubclassableWeakrefTestCase(TestBase):

    def test_subclass_refs(self):
        class MyRef(weakref.ref):
            def __init__(self, ob, callback=None, value=42):
                self.value = value
                super().__init__(ob, callback)
            def __call__(self):
                self.called = True
                return super().__call__()
        o = Object("foo")
        mr = MyRef(o, value=24)
        self.assertTrue(mr() is o)
        self.assertTrue(mr.called)
        self.assertEqual(mr.value, 24)
        del o
        self.assertTrue(mr() is None)
        self.assertTrue(mr.called)

    def test_subclass_refs_dont_replace_standard_refs(self):
        class MyRef(weakref.ref):
            pass
        o = Object(42)
        r1 = MyRef(o)
        r2 = weakref.ref(o)
        self.assertTrue(r1 is not r2)
        self.assertEqual(weakref.getweakrefs(o), [r2, r1])
        self.assertEqual(weakref.getweakrefcount(o), 2)
        r3 = MyRef(o)
        self.assertEqual(weakref.getweakrefcount(o), 3)
        refs = weakref.getweakrefs(o)
        self.assertEqual(len(refs), 3)
        self.assertTrue(r2 is refs[0])
        self.assertIn(r1, refs[1:])
        self.assertIn(r3, refs[1:])

    def test_subclass_refs_dont_conflate_callbacks(self):
        class MyRef(weakref.ref):
            pass
        o = Object(42)
        r1 = MyRef(o, id)
        r2 = MyRef(o, str)
        self.assertTrue(r1 is not r2)
        refs = weakref.getweakrefs(o)
        self.assertIn(r1, refs)
        self.assertIn(r2, refs)

    def test_subclass_refs_with_slots(self):
        class MyRef(weakref.ref):
            __slots__ = "slot1", "slot2"
            def __new__(type, ob, callback, slot1, slot2):
                return weakref.ref.__new__(type, ob, callback)
            def __init__(self, ob, callback, slot1, slot2):
                self.slot1 = slot1
                self.slot2 = slot2
            def meth(self):
                return self.slot1 + self.slot2
        o = Object(42)
        r = MyRef(o, None, "abc", "def")
        self.assertEqual(r.slot1, "abc")
        self.assertEqual(r.slot2, "def")
        self.assertEqual(r.meth(), "abcdef")
        self.assertFalse(hasattr(r, "__dict__"))

    def test_subclass_refs_with_cycle(self):
        # Bug #3110
        # An instance of a weakref subclass can have attributes.
        # If such a weakref holds the only strong reference to the object,
        # deleting the weakref will delete the object. In this case,
        # the callback must not be called, because the ref object is
        # being deleted.
        class MyRef(weakref.ref):
            pass

        # Use a local callback, for "regrtest -R::"
        # to detect refcounting problems
        def callback(w):
            self.cbcalled += 1

        o = C()
        r1 = MyRef(o, callback)
        r1.o = o
        del o

        del r1 # Used to crash here

        self.assertEqual(self.cbcalled, 0)

        # Same test, with two weakrefs to the same object
        # (since code paths are different)
        o = C()
        r1 = MyRef(o, callback)
        r2 = MyRef(o, callback)
        r1.r = r2
        r2.o = o
        del o
        del r2

        del r1 # Used to crash here

        self.assertEqual(self.cbcalled, 0)


class Object:
    def __init__(self, arg):
        self.arg = arg
    def __repr__(self):
        return "<Object %r>" % self.arg
    def __eq__(self, other):
        if isinstance(other, Object):
            return self.arg == other.arg
        return NotImplemented
    def __lt__(self, other):
        if isinstance(other, Object):
            return self.arg < other.arg
        return NotImplemented
    def __hash__(self):
        return hash(self.arg)

class RefCycle:
    def __init__(self):
        self.cycle = self


class MappingTestCase(TestBase):

    COUNT = 10

    def check_len_cycles(self, dict_type, cons):
        N = 20
        items = [RefCycle() for i in range(N)]
        dct = dict_type(cons(o) for o in items)
        # Keep an iterator alive
        it = dct.items()
        try:
            next(it)
        except StopIteration:
            pass
        del items
        gc.collect()
        n1 = len(dct)
        del it
        gc.collect()
        n2 = len(dct)
        # one item may be kept alive inside the iterator
        self.assertIn(n1, (0, 1))
        self.assertEqual(n2, 0)

    def test_weak_keyed_len_cycles(self):
        self.check_len_cycles(weakref.WeakKeyDictionary, lambda k: (k, 1))

    def test_weak_valued_len_cycles(self):
        self.check_len_cycles(weakref.WeakValueDictionary, lambda k: (1, k))

    def check_len_race(self, dict_type, cons):
        # Extended sanity checks for len() in the face of cyclic collection
        self.addCleanup(gc.set_threshold, *gc.get_threshold())
        for th in range(1, 100):
            N = 20
            gc.collect(0)
            gc.set_threshold(th, th, th)
            items = [RefCycle() for i in range(N)]
            dct = dict_type(cons(o) for o in items)
            del items
            # All items will be collected at next garbage collection pass
            it = dct.items()
            try:
                next(it)
            except StopIteration:
                pass
            n1 = len(dct)
            del it
            n2 = len(dct)
            self.assertGreaterEqual(n1, 0)
            self.assertLessEqual(n1, N)
            self.assertGreaterEqual(n2, 0)
            self.assertLessEqual(n2, n1)

    def test_weak_keyed_len_race(self):
        self.check_len_race(weakref.WeakKeyDictionary, lambda k: (k, 1))

    def test_weak_valued_len_race(self):
        self.check_len_race(weakref.WeakValueDictionary, lambda k: (1, k))

    def test_weak_values(self):
        #
        #  This exercises d.copy(), d.items(), d[], del d[], len(d).
        #
        dict, objects = self.make_weak_valued_dict()
        for o in objects:
            self.assertEqual(weakref.getweakrefcount(o), 1)
            self.assertTrue(o is dict[o.arg],
                         "wrong object returned by weak dict!")
        items1 = list(dict.items())
        items2 = list(dict.copy().items())
        items1.sort()
        items2.sort()
        self.assertEqual(items1, items2,
                     "cloning of weak-valued dictionary did not work!")
        del items1, items2
        self.assertEqual(len(dict), self.COUNT)
        del objects[0]
        self.assertEqual(len(dict), self.COUNT - 1,
                     "deleting object did not cause dictionary update")
        del objects, o
        self.assertEqual(len(dict), 0,
                     "deleting the values did not clear the dictionary")
        # regression on SF bug #447152:
        dict = weakref.WeakValueDictionary()
        self.assertRaises(KeyError, dict.__getitem__, 1)
        dict[2] = C()
        self.assertRaises(KeyError, dict.__getitem__, 2)

    def test_weak_keys(self):
        #
        #  This exercises d.copy(), d.items(), d[] = v, d[], del d[],
        #  len(d), k in d.
        #
        dict, objects = self.make_weak_keyed_dict()
        for o in objects:
            self.assertTrue(weakref.getweakrefcount(o) == 1,
                         "wrong number of weak references to %r!" % o)
            self.assertTrue(o.arg is dict[o],
                         "wrong object returned by weak dict!")
        items1 = dict.items()
        items2 = dict.copy().items()
        self.assertEqual(set(items1), set(items2),
                     "cloning of weak-keyed dictionary did not work!")
        del items1, items2
        self.assertEqual(len(dict), self.COUNT)
        del objects[0]
        self.assertTrue(len(dict) == (self.COUNT - 1),
                     "deleting object did not cause dictionary update")
        del objects, o
        self.assertTrue(len(dict) == 0,
                     "deleting the keys did not clear the dictionary")
        o = Object(42)
        dict[o] = "What is the meaning of the universe?"
        self.assertIn(o, dict)
        self.assertNotIn(34, dict)

    def test_weak_keyed_iters(self):
        dict, objects = self.make_weak_keyed_dict()
        self.check_iters(dict)

        # Test keyrefs()
        refs = dict.keyrefs()
        self.assertEqual(len(refs), len(objects))
        objects2 = list(objects)
        for wr in refs:
            ob = wr()
            self.assertIn(ob, dict)
            self.assertIn(ob, dict)
            self.assertEqual(ob.arg, dict[ob])
            objects2.remove(ob)
        self.assertEqual(len(objects2), 0)

        # Test iterkeyrefs()
        objects2 = list(objects)
        self.assertEqual(len(list(dict.keyrefs())), len(objects))
        for wr in dict.keyrefs():
            ob = wr()
            self.assertIn(ob, dict)
            self.assertIn(ob, dict)
            self.assertEqual(ob.arg, dict[ob])
            objects2.remove(ob)
        self.assertEqual(len(objects2), 0)

    def test_weak_valued_iters(self):
        dict, objects = self.make_weak_valued_dict()
        self.check_iters(dict)

        # Test valuerefs()
        refs = dict.valuerefs()
        self.assertEqual(len(refs), len(objects))
        objects2 = list(objects)
        for wr in refs:
            ob = wr()
            self.assertEqual(ob, dict[ob.arg])
            self.assertEqual(ob.arg, dict[ob.arg].arg)
            objects2.remove(ob)
        self.assertEqual(len(objects2), 0)

        # Test itervaluerefs()
        objects2 = list(objects)
        self.assertEqual(len(list(dict.itervaluerefs())), len(objects))
        for wr in dict.itervaluerefs():
            ob = wr()
            self.assertEqual(ob, dict[ob.arg])
            self.assertEqual(ob.arg, dict[ob.arg].arg)
            objects2.remove(ob)
        self.assertEqual(len(objects2), 0)

    def check_iters(self, dict):
        # item iterator:
        items = list(dict.items())
        for item in dict.items():
            items.remove(item)
        self.assertFalse(items, "items() did not touch all items")

        # key iterator, via __iter__():
        keys = list(dict.keys())
        for k in dict:
            keys.remove(k)
        self.assertFalse(keys, "__iter__() did not touch all keys")

        # key iterator, via iterkeys():
        keys = list(dict.keys())
        for k in dict.keys():
            keys.remove(k)
        self.assertFalse(keys, "iterkeys() did not touch all keys")

        # value iterator:
        values = list(dict.values())
        for v in dict.values():
            values.remove(v)
        self.assertFalse(values,
                     "itervalues() did not touch all values")

    def check_weak_destroy_while_iterating(self, dict, objects, iter_name):
        n = len(dict)
        it = iter(getattr(dict, iter_name)())
        next(it)             # Trigger internal iteration
        # Destroy an object
        del objects[-1]
        gc.collect()    # just in case
        # We have removed either the first consumed object, or another one
        self.assertIn(len(list(it)), [len(objects), len(objects) - 1])
        del it
        # The removal has been committed
        self.assertEqual(len(dict), n - 1)

    def check_weak_destroy_and_mutate_while_iterating(self, dict, testcontext):
        # Check that we can explicitly mutate the weak dict without
        # interfering with delayed removal.
        # `testcontext` should create an iterator, destroy one of the
        # weakref'ed objects and then return a new key/value pair corresponding
        # to the destroyed object.
        with testcontext() as (k, v):
            self.assertNotIn(k, dict)
        with testcontext() as (k, v):
            self.assertRaises(KeyError, dict.__delitem__, k)
        self.assertNotIn(k, dict)
        with testcontext() as (k, v):
            self.assertRaises(KeyError, dict.pop, k)
        self.assertNotIn(k, dict)
        with testcontext() as (k, v):
            dict[k] = v
        self.assertEqual(dict[k], v)
        ddict = copy.copy(dict)
        with testcontext() as (k, v):
            dict.update(ddict)
        self.assertEqual(dict, ddict)
        with testcontext() as (k, v):
            dict.clear()
        self.assertEqual(len(dict), 0)

    def test_weak_keys_destroy_while_iterating(self):
        # Issue #7105: iterators shouldn't crash when a key is implicitly removed
        dict, objects = self.make_weak_keyed_dict()
        self.check_weak_destroy_while_iterating(dict, objects, 'keys')
        self.check_weak_destroy_while_iterating(dict, objects, 'items')
        self.check_weak_destroy_while_iterating(dict, objects, 'values')
        self.check_weak_destroy_while_iterating(dict, objects, 'keyrefs')
        dict, objects = self.make_weak_keyed_dict()
        @contextlib.contextmanager
        def testcontext():
            try:
                it = iter(dict.items())
                next(it)
                # Schedule a key/value for removal and recreate it
                v = objects.pop().arg
                gc.collect()      # just in case
                yield Object(v), v
            finally:
                it = None           # should commit all removals
        self.check_weak_destroy_and_mutate_while_iterating(dict, testcontext)

    def test_weak_values_destroy_while_iterating(self):
        # Issue #7105: iterators shouldn't crash when a key is implicitly removed
        dict, objects = self.make_weak_valued_dict()
        self.check_weak_destroy_while_iterating(dict, objects, 'keys')
        self.check_weak_destroy_while_iterating(dict, objects, 'items')
        self.check_weak_destroy_while_iterating(dict, objects, 'values')
        self.check_weak_destroy_while_iterating(dict, objects, 'itervaluerefs')
        self.check_weak_destroy_while_iterating(dict, objects, 'valuerefs')
        dict, objects = self.make_weak_valued_dict()
        @contextlib.contextmanager
        def testcontext():
            try:
                it = iter(dict.items())
                next(it)
                # Schedule a key/value for removal and recreate it
                k = objects.pop().arg
                gc.collect()      # just in case
                yield k, Object(k)
            finally:
                it = None           # should commit all removals
        self.check_weak_destroy_and_mutate_while_iterating(dict, testcontext)

    def test_make_weak_keyed_dict_from_dict(self):
        o = Object(3)
        dict = weakref.WeakKeyDictionary({o:364})
        self.assertEqual(dict[o], 364)

    def test_make_weak_keyed_dict_from_weak_keyed_dict(self):
        o = Object(3)
        dict = weakref.WeakKeyDictionary({o:364})
        dict2 = weakref.WeakKeyDictionary(dict)
        self.assertEqual(dict[o], 364)

    def make_weak_keyed_dict(self):
        dict = weakref.WeakKeyDictionary()
        objects = list(map(Object, range(self.COUNT)))
        for o in objects:
            dict[o] = o.arg
        return dict, objects

    def test_make_weak_valued_dict_from_dict(self):
        o = Object(3)
        dict = weakref.WeakValueDictionary({364:o})
        self.assertEqual(dict[364], o)

    def test_make_weak_valued_dict_from_weak_valued_dict(self):
        o = Object(3)
        dict = weakref.WeakValueDictionary({364:o})
        dict2 = weakref.WeakValueDictionary(dict)
        self.assertEqual(dict[364], o)

    def make_weak_valued_dict(self):
        dict = weakref.WeakValueDictionary()
        objects = list(map(Object, range(self.COUNT)))
        for o in objects:
            dict[o.arg] = o
        return dict, objects

    def check_popitem(self, klass, key1, value1, key2, value2):
        weakdict = klass()
        weakdict[key1] = value1
        weakdict[key2] = value2
        self.assertEqual(len(weakdict), 2)
        k, v = weakdict.popitem()
        self.assertEqual(len(weakdict), 1)
        if k is key1:
            self.assertTrue(v is value1)
        else:
            self.assertTrue(v is value2)
        k, v = weakdict.popitem()
        self.assertEqual(len(weakdict), 0)
        if k is key1:
            self.assertTrue(v is value1)
        else:
            self.assertTrue(v is value2)

    def test_weak_valued_dict_popitem(self):
        self.check_popitem(weakref.WeakValueDictionary,
                           "key1", C(), "key2", C())

    def test_weak_keyed_dict_popitem(self):
        self.check_popitem(weakref.WeakKeyDictionary,
                           C(), "value 1", C(), "value 2")

    def check_setdefault(self, klass, key, value1, value2):
        self.assertTrue(value1 is not value2,
                     "invalid test"
                     " -- value parameters must be distinct objects")
        weakdict = klass()
        o = weakdict.setdefault(key, value1)
        self.assertTrue(o is value1)
        self.assertIn(key, weakdict)
        self.assertTrue(weakdict.get(key) is value1)
        self.assertTrue(weakdict[key] is value1)

        o = weakdict.setdefault(key, value2)
        self.assertTrue(o is value1)
        self.assertIn(key, weakdict)
        self.assertTrue(weakdict.get(key) is value1)
        self.assertTrue(weakdict[key] is value1)

    def test_weak_valued_dict_setdefault(self):
        self.check_setdefault(weakref.WeakValueDictionary,
                              "key", C(), C())

    def test_weak_keyed_dict_setdefault(self):
        self.check_setdefault(weakref.WeakKeyDictionary,
                              C(), "value 1", "value 2")

    def check_update(self, klass, dict):
        #
        #  This exercises d.update(), len(d), d.keys(), k in d,
        #  d.get(), d[].
        #
        weakdict = klass()
        weakdict.update(dict)
        self.assertEqual(len(weakdict), len(dict))
        for k in weakdict.keys():
            self.assertIn(k, dict, "mysterious new key appeared in weak dict")
            v = dict.get(k)
            self.assertTrue(v is weakdict[k])
            self.assertTrue(v is weakdict.get(k))
        for k in dict.keys():
            self.assertIn(k, weakdict, "original key disappeared in weak dict")
            v = dict[k]
            self.assertTrue(v is weakdict[k])
            self.assertTrue(v is weakdict.get(k))

    def test_weak_valued_dict_update(self):
        self.check_update(weakref.WeakValueDictionary,
                          {1: C(), 'a': C(), C(): C()})

    def test_weak_keyed_dict_update(self):
        self.check_update(weakref.WeakKeyDictionary,
                          {C(): 1, C(): 2, C(): 3})

    def test_weak_keyed_delitem(self):
        d = weakref.WeakKeyDictionary()
        o1 = Object('1')
        o2 = Object('2')
        d[o1] = 'something'
        d[o2] = 'something'
        self.assertEqual(len(d), 2)
        del d[o1]
        self.assertEqual(len(d), 1)
        self.assertEqual(list(d.keys()), [o2])

    def test_weak_valued_delitem(self):
        d = weakref.WeakValueDictionary()
        o1 = Object('1')
        o2 = Object('2')
        d['something'] = o1
        d['something else'] = o2
        self.assertEqual(len(d), 2)
        del d['something']
        self.assertEqual(len(d), 1)
        self.assertTrue(list(d.items()) == [('something else', o2)])

    def test_weak_keyed_bad_delitem(self):
        d = weakref.WeakKeyDictionary()
        o = Object('1')
        # An attempt to delete an object that isn't there should raise
        # KeyError.  It didn't before 2.3.
        self.assertRaises(KeyError, d.__delitem__, o)
        self.assertRaises(KeyError, d.__getitem__, o)

        # If a key isn't of a weakly referencable type, __getitem__ and
        # __setitem__ raise TypeError.  __delitem__ should too.
        self.assertRaises(TypeError, d.__delitem__,  13)
        self.assertRaises(TypeError, d.__getitem__,  13)
        self.assertRaises(TypeError, d.__setitem__,  13, 13)

    def test_weak_keyed_cascading_deletes(self):
        # SF bug 742860.  For some reason, before 2.3 __delitem__ iterated
        # over the keys via self.data.iterkeys().  If things vanished from
        # the dict during this (or got added), that caused a RuntimeError.

        d = weakref.WeakKeyDictionary()
        mutate = False

        class C(object):
            def __init__(self, i):
                self.value = i
            def __hash__(self):
                return hash(self.value)
            def __eq__(self, other):
                if mutate:
                    # Side effect that mutates the dict, by removing the
                    # last strong reference to a key.
                    del objs[-1]
                return self.value == other.value

        objs = [C(i) for i in range(4)]
        for o in objs:
            d[o] = o.value
        del o   # now the only strong references to keys are in objs
        # Find the order in which iterkeys sees the keys.
        objs = list(d.keys())
        # Reverse it, so that the iteration implementation of __delitem__
        # has to keep looping to find the first object we delete.
        objs.reverse()

        # Turn on mutation in C.__eq__.  The first time thru the loop,
        # under the iterkeys() business the first comparison will delete
        # the last item iterkeys() would see, and that causes a
        #     RuntimeError: dictionary changed size during iteration
        # when the iterkeys() loop goes around to try comparing the next
        # key.  After this was fixed, it just deletes the last object *our*
        # "for o in obj" loop would have gotten to.
        mutate = True
        count = 0
        for o in objs:
            count += 1
            del d[o]
        self.assertEqual(len(d), 0)
        self.assertEqual(count, 2)

from test import mapping_tests

class WeakValueDictionaryTestCase(mapping_tests.BasicTestMappingProtocol):
    """Check that WeakValueDictionary conforms to the mapping protocol"""
    __ref = {"key1":Object(1), "key2":Object(2), "key3":Object(3)}
    type2test = weakref.WeakValueDictionary
    def _reference(self):
        return self.__ref.copy()

class WeakKeyDictionaryTestCase(mapping_tests.BasicTestMappingProtocol):
    """Check that WeakKeyDictionary conforms to the mapping protocol"""
    __ref = {Object("key1"):1, Object("key2"):2, Object("key3"):3}
    type2test = weakref.WeakKeyDictionary
    def _reference(self):
        return self.__ref.copy()

libreftest = """ Doctest for examples in the library reference: weakref.rst

>>> import weakref
>>> class Dict(dict):
...     pass
...
>>> obj = Dict(red=1, green=2, blue=3)   # this object is weak referencable
>>> r = weakref.ref(obj)
>>> print(r() is obj)
True

>>> import weakref
>>> class Object:
...     pass
...
>>> o = Object()
>>> r = weakref.ref(o)
>>> o2 = r()
>>> o is o2
True
>>> del o, o2
>>> print(r())
None

>>> import weakref
>>> class ExtendedRef(weakref.ref):
...     def __init__(self, ob, callback=None, **annotations):
...         super().__init__(ob, callback)
...         self.__counter = 0
...         for k, v in annotations.items():
...             setattr(self, k, v)
...     def __call__(self):
...         '''Return a pair containing the referent and the number of
...         times the reference has been called.
...         '''
...         ob = super().__call__()
...         if ob is not None:
...             self.__counter += 1
...             ob = (ob, self.__counter)
...         return ob
...
>>> class A:   # not in docs from here, just testing the ExtendedRef
...     pass
...
>>> a = A()
>>> r = ExtendedRef(a, foo=1, bar="baz")
>>> r.foo
1
>>> r.bar
'baz'
>>> r()[1]
1
>>> r()[1]
2
>>> r()[0] is a
True


>>> import weakref
>>> _id2obj_dict = weakref.WeakValueDictionary()
>>> def remember(obj):
...     oid = id(obj)
...     _id2obj_dict[oid] = obj
...     return oid
...
>>> def id2obj(oid):
...     return _id2obj_dict[oid]
...
>>> a = A()             # from here, just testing
>>> a_id = remember(a)
>>> id2obj(a_id) is a
True
>>> del a
>>> try:
...     id2obj(a_id)
... except KeyError:
...     print('OK')
... else:
...     print('WeakValueDictionary error')
OK

"""

__test__ = {'libreftest' : libreftest}

def test_main():
    support.run_unittest(
        ReferencesTestCase,
        MappingTestCase,
        WeakValueDictionaryTestCase,
        WeakKeyDictionaryTestCase,
        SubclassableWeakrefTestCase,
        )
    support.run_doctest(sys.modules[__name__])


if __name__ == "__main__":
    test_main()