summaryrefslogtreecommitdiffstats
path: root/Lib/test/test_traceback.py
blob: bffc03e663ff787f29c0bb9c8fcb9ace7586bc09 (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
"""Test cases for traceback module"""

from collections import namedtuple
from io import StringIO
import linecache
import sys
import unittest
import re
from test import support
from test.support import TESTFN, Error, captured_output, unlink, cpython_only
from test.support.script_helper import assert_python_ok
import textwrap

import traceback


test_code = namedtuple('code', ['co_filename', 'co_name'])
test_frame = namedtuple('frame', ['f_code', 'f_globals', 'f_locals'])
test_tb = namedtuple('tb', ['tb_frame', 'tb_lineno', 'tb_next'])


class TracebackCases(unittest.TestCase):
    # For now, a very minimal set of tests.  I want to be sure that
    # formatting of SyntaxErrors works based on changes for 2.1.

    def get_exception_format(self, func, exc):
        try:
            func()
        except exc as value:
            return traceback.format_exception_only(exc, value)
        else:
            raise ValueError("call did not raise exception")

    def syntax_error_with_caret(self):
        compile("def fact(x):\n\treturn x!\n", "?", "exec")

    def syntax_error_with_caret_2(self):
        compile("1 +\n", "?", "exec")

    def syntax_error_bad_indentation(self):
        compile("def spam():\n  print(1)\n print(2)", "?", "exec")

    def syntax_error_with_caret_non_ascii(self):
        compile('Python = "\u1e54\xfd\u0163\u0125\xf2\xf1" +', "?", "exec")

    def syntax_error_bad_indentation2(self):
        compile(" print(2)", "?", "exec")

    def test_caret(self):
        err = self.get_exception_format(self.syntax_error_with_caret,
                                        SyntaxError)
        self.assertEqual(len(err), 4)
        self.assertTrue(err[1].strip() == "return x!")
        self.assertIn("^", err[2]) # third line has caret
        self.assertEqual(err[1].find("!"), err[2].find("^")) # in the right place

        err = self.get_exception_format(self.syntax_error_with_caret_2,
                                        SyntaxError)
        self.assertIn("^", err[2]) # third line has caret
        self.assertEqual(err[2].count('\n'), 1)   # and no additional newline
        self.assertEqual(err[1].find("+"), err[2].find("^"))  # in the right place

        err = self.get_exception_format(self.syntax_error_with_caret_non_ascii,
                                        SyntaxError)
        self.assertIn("^", err[2]) # third line has caret
        self.assertEqual(err[2].count('\n'), 1)   # and no additional newline
        self.assertEqual(err[1].find("+"), err[2].find("^"))  # in the right place

    def test_nocaret(self):
        exc = SyntaxError("error", ("x.py", 23, None, "bad syntax"))
        err = traceback.format_exception_only(SyntaxError, exc)
        self.assertEqual(len(err), 3)
        self.assertEqual(err[1].strip(), "bad syntax")

    def test_bad_indentation(self):
        err = self.get_exception_format(self.syntax_error_bad_indentation,
                                        IndentationError)
        self.assertEqual(len(err), 4)
        self.assertEqual(err[1].strip(), "print(2)")
        self.assertIn("^", err[2])
        self.assertEqual(err[1].find(")"), err[2].find("^"))

        err = self.get_exception_format(self.syntax_error_bad_indentation2,
                                        IndentationError)
        self.assertEqual(len(err), 4)
        self.assertEqual(err[1].strip(), "print(2)")
        self.assertIn("^", err[2])
        self.assertEqual(err[1].find("p"), err[2].find("^"))

    def test_base_exception(self):
        # Test that exceptions derived from BaseException are formatted right
        e = KeyboardInterrupt()
        lst = traceback.format_exception_only(e.__class__, e)
        self.assertEqual(lst, ['KeyboardInterrupt\n'])

    def test_format_exception_only_bad__str__(self):
        class X(Exception):
            def __str__(self):
                1/0
        err = traceback.format_exception_only(X, X())
        self.assertEqual(len(err), 1)
        str_value = '<unprintable %s object>' % X.__name__
        if X.__module__ in ('__main__', 'builtins'):
            str_name = X.__qualname__
        else:
            str_name = '.'.join([X.__module__, X.__qualname__])
        self.assertEqual(err[0], "%s: %s\n" % (str_name, str_value))

    def test_encoded_file(self):
        # Test that tracebacks are correctly printed for encoded source files:
        # - correct line number (Issue2384)
        # - respect file encoding (Issue3975)
        import tempfile, sys, subprocess, os

        # The spawned subprocess has its stdout redirected to a PIPE, and its
        # encoding may be different from the current interpreter, on Windows
        # at least.
        process = subprocess.Popen([sys.executable, "-c",
                                    "import sys; print(sys.stdout.encoding)"],
                                   stdout=subprocess.PIPE,
                                   stderr=subprocess.STDOUT)
        stdout, stderr = process.communicate()
        output_encoding = str(stdout, 'ascii').splitlines()[0]

        def do_test(firstlines, message, charset, lineno):
            # Raise the message in a subprocess, and catch the output
            try:
                with open(TESTFN, "w", encoding=charset) as output:
                    output.write("""{0}if 1:
                        import traceback;
                        raise RuntimeError('{1}')
                        """.format(firstlines, message))

                process = subprocess.Popen([sys.executable, TESTFN],
                    stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
                stdout, stderr = process.communicate()
                stdout = stdout.decode(output_encoding).splitlines()
            finally:
                unlink(TESTFN)

            # The source lines are encoded with the 'backslashreplace' handler
            encoded_message = message.encode(output_encoding,
                                             'backslashreplace')
            # and we just decoded them with the output_encoding.
            message_ascii = encoded_message.decode(output_encoding)

            err_line = "raise RuntimeError('{0}')".format(message_ascii)
            err_msg = "RuntimeError: {0}".format(message_ascii)

            self.assertIn(("line %s" % lineno), stdout[1],
                "Invalid line number: {0!r} instead of {1}".format(
                    stdout[1], lineno))
            self.assertTrue(stdout[2].endswith(err_line),
                "Invalid traceback line: {0!r} instead of {1!r}".format(
                    stdout[2], err_line))
            self.assertTrue(stdout[3] == err_msg,
                "Invalid error message: {0!r} instead of {1!r}".format(
                    stdout[3], err_msg))

        do_test("", "foo", "ascii", 3)
        for charset in ("ascii", "iso-8859-1", "utf-8", "GBK"):
            if charset == "ascii":
                text = "foo"
            elif charset == "GBK":
                text = "\u4E02\u5100"
            else:
                text = "h\xe9 ho"
            do_test("# coding: {0}\n".format(charset),
                    text, charset, 4)
            do_test("#!shebang\n# coding: {0}\n".format(charset),
                    text, charset, 5)
            do_test(" \t\f\n# coding: {0}\n".format(charset),
                    text, charset, 5)
        # Issue #18960: coding spec should have no effect
        do_test("x=0\n# coding: GBK\n", "h\xe9 ho", 'utf-8', 5)

    @support.requires_type_collecting
    def test_print_traceback_at_exit(self):
        # Issue #22599: Ensure that it is possible to use the traceback module
        # to display an exception at Python exit
        code = textwrap.dedent("""
            import sys
            import traceback

            class PrintExceptionAtExit(object):
                def __init__(self):
                    try:
                        x = 1 / 0
                    except Exception:
                        self.exc_info = sys.exc_info()
                        # self.exc_info[1] (traceback) contains frames:
                        # explicitly clear the reference to self in the current
                        # frame to break a reference cycle
                        self = None

                def __del__(self):
                    traceback.print_exception(*self.exc_info)

            # Keep a reference in the module namespace to call the destructor
            # when the module is unloaded
            obj = PrintExceptionAtExit()
        """)
        rc, stdout, stderr = assert_python_ok('-c', code)
        expected = [b'Traceback (most recent call last):',
                    b'  File "<string>", line 8, in __init__',
                    b'ZeroDivisionError: division by zero']
        self.assertEqual(stderr.splitlines(), expected)

    def test_print_exception(self):
        output = StringIO()
        traceback.print_exception(
            Exception, Exception("projector"), None, file=output
        )
        self.assertEqual(output.getvalue(), "Exception: projector\n")


class TracebackFormatTests(unittest.TestCase):

    def some_exception(self):
        raise KeyError('blah')

    @cpython_only
    def check_traceback_format(self, cleanup_func=None):
        from _testcapi import traceback_print
        try:
            self.some_exception()
        except KeyError:
            type_, value, tb = sys.exc_info()
            if cleanup_func is not None:
                # Clear the inner frames, not this one
                cleanup_func(tb.tb_next)
            traceback_fmt = 'Traceback (most recent call last):\n' + \
                            ''.join(traceback.format_tb(tb))
            file_ = StringIO()
            traceback_print(tb, file_)
            python_fmt  = file_.getvalue()
            # Call all _tb and _exc functions
            with captured_output("stderr") as tbstderr:
                traceback.print_tb(tb)
            tbfile = StringIO()
            traceback.print_tb(tb, file=tbfile)
            with captured_output("stderr") as excstderr:
                traceback.print_exc()
            excfmt = traceback.format_exc()
            excfile = StringIO()
            traceback.print_exc(file=excfile)
        else:
            raise Error("unable to create test traceback string")

        # Make sure that Python and the traceback module format the same thing
        self.assertEqual(traceback_fmt, python_fmt)
        # Now verify the _tb func output
        self.assertEqual(tbstderr.getvalue(), tbfile.getvalue())
        # Now verify the _exc func output
        self.assertEqual(excstderr.getvalue(), excfile.getvalue())
        self.assertEqual(excfmt, excfile.getvalue())

        # Make sure that the traceback is properly indented.
        tb_lines = python_fmt.splitlines()
        self.assertEqual(len(tb_lines), 5)
        banner = tb_lines[0]
        location, source_line = tb_lines[-2:]
        self.assertTrue(banner.startswith('Traceback'))
        self.assertTrue(location.startswith('  File'))
        self.assertTrue(source_line.startswith('    raise'))

    def test_traceback_format(self):
        self.check_traceback_format()

    def test_traceback_format_with_cleared_frames(self):
        # Check that traceback formatting also works with a clear()ed frame
        def cleanup_tb(tb):
            tb.tb_frame.clear()
        self.check_traceback_format(cleanup_tb)

    def test_stack_format(self):
        # Verify _stack functions. Note we have to use _getframe(1) to
        # compare them without this frame appearing in the output
        with captured_output("stderr") as ststderr:
            traceback.print_stack(sys._getframe(1))
        stfile = StringIO()
        traceback.print_stack(sys._getframe(1), file=stfile)
        self.assertEqual(ststderr.getvalue(), stfile.getvalue())

        stfmt = traceback.format_stack(sys._getframe(1))

        self.assertEqual(ststderr.getvalue(), "".join(stfmt))

    def test_print_stack(self):
        def prn():
            traceback.print_stack()
        with captured_output("stderr") as stderr:
            prn()
        lineno = prn.__code__.co_firstlineno
        self.assertEqual(stderr.getvalue().splitlines()[-4:], [
            '  File "%s", line %d, in test_print_stack' % (__file__, lineno+3),
            '    prn()',
            '  File "%s", line %d, in prn' % (__file__, lineno+1),
            '    traceback.print_stack()',
        ])

    # issue 26823 - Shrink recursive tracebacks
    def _check_recursive_traceback_display(self, render_exc):
        # Always show full diffs when this test fails
        # Note that rearranging things may require adjusting
        # the relative line numbers in the expected tracebacks
        self.maxDiff = None

        # Check hitting the recursion limit
        def f():
            f()

        with captured_output("stderr") as stderr_f:
            try:
                f()
            except RecursionError as exc:
                render_exc()
            else:
                self.fail("no recursion occurred")

        lineno_f = f.__code__.co_firstlineno
        result_f = (
            'Traceback (most recent call last):\n'
            f'  File "{__file__}", line {lineno_f+5}, in _check_recursive_traceback_display\n'
            '    f()\n'
            f'  File "{__file__}", line {lineno_f+1}, in f\n'
            '    f()\n'
            f'  File "{__file__}", line {lineno_f+1}, in f\n'
            '    f()\n'
            f'  File "{__file__}", line {lineno_f+1}, in f\n'
            '    f()\n'
            # XXX: The following line changes depending on whether the tests
            # are run through the interactive interpreter or with -m
            # It also varies depending on the platform (stack size)
            # Fortunately, we don't care about exactness here, so we use regex
            r'  \[Previous line repeated (\d+) more times\]' '\n'
            'RecursionError: maximum recursion depth exceeded\n'
        )

        expected = result_f.splitlines()
        actual = stderr_f.getvalue().splitlines()

        # Check the output text matches expectations
        # 2nd last line contains the repetition count
        self.assertEqual(actual[:-2], expected[:-2])
        self.assertRegex(actual[-2], expected[-2])
        # last line can have additional text appended
        self.assertIn(expected[-1], actual[-1])

        # Check the recursion count is roughly as expected
        rec_limit = sys.getrecursionlimit()
        self.assertIn(int(re.search(r"\d+", actual[-2]).group()), range(rec_limit-60, rec_limit))

        # Check a known (limited) number of recursive invocations
        def g(count=10):
            if count:
                return g(count-1)
            raise ValueError

        with captured_output("stderr") as stderr_g:
            try:
                g()
            except ValueError as exc:
                render_exc()
            else:
                self.fail("no value error was raised")

        lineno_g = g.__code__.co_firstlineno
        result_g = (
            f'  File "{__file__}", line {lineno_g+2}, in g\n'
            '    return g(count-1)\n'
            f'  File "{__file__}", line {lineno_g+2}, in g\n'
            '    return g(count-1)\n'
            f'  File "{__file__}", line {lineno_g+2}, in g\n'
            '    return g(count-1)\n'
            '  [Previous line repeated 6 more times]\n'
            f'  File "{__file__}", line {lineno_g+3}, in g\n'
            '    raise ValueError\n'
            'ValueError\n'
        )
        tb_line = (
            'Traceback (most recent call last):\n'
            f'  File "{__file__}", line {lineno_g+7}, in _check_recursive_traceback_display\n'
            '    g()\n'
        )
        expected = (tb_line + result_g).splitlines()
        actual = stderr_g.getvalue().splitlines()
        self.assertEqual(actual, expected)

        # Check 2 different repetitive sections
        def h(count=10):
            if count:
                return h(count-1)
            g()

        with captured_output("stderr") as stderr_h:
            try:
                h()
            except ValueError as exc:
                render_exc()
            else:
                self.fail("no value error was raised")

        lineno_h = h.__code__.co_firstlineno
        result_h = (
            'Traceback (most recent call last):\n'
            f'  File "{__file__}", line {lineno_h+7}, in _check_recursive_traceback_display\n'
            '    h()\n'
            f'  File "{__file__}", line {lineno_h+2}, in h\n'
            '    return h(count-1)\n'
            f'  File "{__file__}", line {lineno_h+2}, in h\n'
            '    return h(count-1)\n'
            f'  File "{__file__}", line {lineno_h+2}, in h\n'
            '    return h(count-1)\n'
            '  [Previous line repeated 6 more times]\n'
            f'  File "{__file__}", line {lineno_h+3}, in h\n'
            '    g()\n'
        )
        expected = (result_h + result_g).splitlines()
        actual = stderr_h.getvalue().splitlines()
        self.assertEqual(actual, expected)

    def test_recursive_traceback_python(self):
        self._check_recursive_traceback_display(traceback.print_exc)

    @cpython_only
    def test_recursive_traceback_cpython_internal(self):
        from _testcapi import exception_print
        def render_exc():
            exc_type, exc_value, exc_tb = sys.exc_info()
            exception_print(exc_value)
        self._check_recursive_traceback_display(render_exc)

    def test_format_stack(self):
        def fmt():
            return traceback.format_stack()
        result = fmt()
        lineno = fmt.__code__.co_firstlineno
        self.assertEqual(result[-2:], [
            '  File "%s", line %d, in test_format_stack\n'
            '    result = fmt()\n' % (__file__, lineno+2),
            '  File "%s", line %d, in fmt\n'
            '    return traceback.format_stack()\n' % (__file__, lineno+1),
        ])

    @cpython_only
    def test_unhashable(self):
        from _testcapi import exception_print

        class UnhashableException(Exception):
            def __eq__(self, other):
                return True

        ex1 = UnhashableException('ex1')
        ex2 = UnhashableException('ex2')
        try:
            raise ex2 from ex1
        except UnhashableException:
            try:
                raise ex1
            except UnhashableException:
                exc_type, exc_val, exc_tb = sys.exc_info()

        with captured_output("stderr") as stderr_f:
            exception_print(exc_val)

        tb = stderr_f.getvalue().strip().splitlines()
        self.assertEqual(11, len(tb))
        self.assertEqual(context_message.strip(), tb[5])
        self.assertIn('UnhashableException: ex2', tb[3])
        self.assertIn('UnhashableException: ex1', tb[10])


cause_message = (
    "\nThe above exception was the direct cause "
    "of the following exception:\n\n")

context_message = (
    "\nDuring handling of the above exception, "
    "another exception occurred:\n\n")

boundaries = re.compile(
    '(%s|%s)' % (re.escape(cause_message), re.escape(context_message)))


class BaseExceptionReportingTests:

    def get_exception(self, exception_or_callable):
        if isinstance(exception_or_callable, Exception):
            return exception_or_callable
        try:
            exception_or_callable()
        except Exception as e:
            return e

    def zero_div(self):
        1/0 # In zero_div

    def check_zero_div(self, msg):
        lines = msg.splitlines()
        self.assertTrue(lines[-3].startswith('  File'))
        self.assertIn('1/0 # In zero_div', lines[-2])
        self.assertTrue(lines[-1].startswith('ZeroDivisionError'), lines[-1])

    def test_simple(self):
        try:
            1/0 # Marker
        except ZeroDivisionError as _:
            e = _
        lines = self.get_report(e).splitlines()
        self.assertEqual(len(lines), 4)
        self.assertTrue(lines[0].startswith('Traceback'))
        self.assertTrue(lines[1].startswith('  File'))
        self.assertIn('1/0 # Marker', lines[2])
        self.assertTrue(lines[3].startswith('ZeroDivisionError'))

    def test_cause(self):
        def inner_raise():
            try:
                self.zero_div()
            except ZeroDivisionError as e:
                raise KeyError from e
        def outer_raise():
            inner_raise() # Marker
        blocks = boundaries.split(self.get_report(outer_raise))
        self.assertEqual(len(blocks), 3)
        self.assertEqual(blocks[1], cause_message)
        self.check_zero_div(blocks[0])
        self.assertIn('inner_raise() # Marker', blocks[2])

    def test_context(self):
        def inner_raise():
            try:
                self.zero_div()
            except ZeroDivisionError:
                raise KeyError
        def outer_raise():
            inner_raise() # Marker
        blocks = boundaries.split(self.get_report(outer_raise))
        self.assertEqual(len(blocks), 3)
        self.assertEqual(blocks[1], context_message)
        self.check_zero_div(blocks[0])
        self.assertIn('inner_raise() # Marker', blocks[2])

    def test_context_suppression(self):
        try:
            try:
                raise Exception
            except:
                raise ZeroDivisionError from None
        except ZeroDivisionError as _:
            e = _
        lines = self.get_report(e).splitlines()
        self.assertEqual(len(lines), 4)
        self.assertTrue(lines[0].startswith('Traceback'))
        self.assertTrue(lines[1].startswith('  File'))
        self.assertIn('ZeroDivisionError from None', lines[2])
        self.assertTrue(lines[3].startswith('ZeroDivisionError'))

    def test_cause_and_context(self):
        # When both a cause and a context are set, only the cause should be
        # displayed and the context should be muted.
        def inner_raise():
            try:
                self.zero_div()
            except ZeroDivisionError as _e:
                e = _e
            try:
                xyzzy
            except NameError:
                raise KeyError from e
        def outer_raise():
            inner_raise() # Marker
        blocks = boundaries.split(self.get_report(outer_raise))
        self.assertEqual(len(blocks), 3)
        self.assertEqual(blocks[1], cause_message)
        self.check_zero_div(blocks[0])
        self.assertIn('inner_raise() # Marker', blocks[2])

    def test_cause_recursive(self):
        def inner_raise():
            try:
                try:
                    self.zero_div()
                except ZeroDivisionError as e:
                    z = e
                    raise KeyError from e
            except KeyError as e:
                raise z from e
        def outer_raise():
            inner_raise() # Marker
        blocks = boundaries.split(self.get_report(outer_raise))
        self.assertEqual(len(blocks), 3)
        self.assertEqual(blocks[1], cause_message)
        # The first block is the KeyError raised from the ZeroDivisionError
        self.assertIn('raise KeyError from e', blocks[0])
        self.assertNotIn('1/0', blocks[0])
        # The second block (apart from the boundary) is the ZeroDivisionError
        # re-raised from the KeyError
        self.assertIn('inner_raise() # Marker', blocks[2])
        self.check_zero_div(blocks[2])

    def test_syntax_error_offset_at_eol(self):
        # See #10186.
        def e():
            raise SyntaxError('', ('', 0, 5, 'hello'))
        msg = self.get_report(e).splitlines()
        self.assertEqual(msg[-2], "        ^")
        def e():
            exec("x = 5 | 4 |")
        msg = self.get_report(e).splitlines()
        self.assertEqual(msg[-2], '              ^')

    def test_message_none(self):
        # A message that looks like "None" should not be treated specially
        err = self.get_report(Exception(None))
        self.assertIn('Exception: None\n', err)
        err = self.get_report(Exception('None'))
        self.assertIn('Exception: None\n', err)
        err = self.get_report(Exception())
        self.assertIn('Exception\n', err)
        err = self.get_report(Exception(''))
        self.assertIn('Exception\n', err)


class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
    #
    # This checks reporting through the 'traceback' module, with both
    # format_exception() and print_exception().
    #

    def get_report(self, e):
        e = self.get_exception(e)
        s = ''.join(
            traceback.format_exception(type(e), e, e.__traceback__))
        with captured_output("stderr") as sio:
            traceback.print_exception(type(e), e, e.__traceback__)
        self.assertEqual(sio.getvalue(), s)
        return s


class CExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
    #
    # This checks built-in reporting by the interpreter.
    #

    @cpython_only
    def get_report(self, e):
        from _testcapi import exception_print
        e = self.get_exception(e)
        with captured_output("stderr") as s:
            exception_print(e)
        return s.getvalue()


class LimitTests(unittest.TestCase):

    ''' Tests for limit argument.
        It's enough to test extact_tb, extract_stack and format_exception '''

    def last_raises1(self):
        raise Exception('Last raised')

    def last_raises2(self):
        self.last_raises1()

    def last_raises3(self):
        self.last_raises2()

    def last_raises4(self):
        self.last_raises3()

    def last_raises5(self):
        self.last_raises4()

    def last_returns_frame1(self):
        return sys._getframe()

    def last_returns_frame2(self):
        return self.last_returns_frame1()

    def last_returns_frame3(self):
        return self.last_returns_frame2()

    def last_returns_frame4(self):
        return self.last_returns_frame3()

    def last_returns_frame5(self):
        return self.last_returns_frame4()

    def test_extract_stack(self):
        frame = self.last_returns_frame5()
        def extract(**kwargs):
            return traceback.extract_stack(frame, **kwargs)
        def assertEqualExcept(actual, expected, ignore):
            self.assertEqual(actual[:ignore], expected[:ignore])
            self.assertEqual(actual[ignore+1:], expected[ignore+1:])
            self.assertEqual(len(actual), len(expected))

        with support.swap_attr(sys, 'tracebacklimit', 1000):
            nolim = extract()
            self.assertGreater(len(nolim), 5)
            self.assertEqual(extract(limit=2), nolim[-2:])
            assertEqualExcept(extract(limit=100), nolim[-100:], -5-1)
            self.assertEqual(extract(limit=-2), nolim[:2])
            assertEqualExcept(extract(limit=-100), nolim[:100], len(nolim)-5-1)
            self.assertEqual(extract(limit=0), [])
            del sys.tracebacklimit
            assertEqualExcept(extract(), nolim, -5-1)
            sys.tracebacklimit = 2
            self.assertEqual(extract(), nolim[-2:])
            self.assertEqual(extract(limit=3), nolim[-3:])
            self.assertEqual(extract(limit=-3), nolim[:3])
            sys.tracebacklimit = 0
            self.assertEqual(extract(), [])
            sys.tracebacklimit = -1
            self.assertEqual(extract(), [])

    def test_extract_tb(self):
        try:
            self.last_raises5()
        except Exception:
            exc_type, exc_value, tb = sys.exc_info()
        def extract(**kwargs):
            return traceback.extract_tb(tb, **kwargs)

        with support.swap_attr(sys, 'tracebacklimit', 1000):
            nolim = extract()
            self.assertEqual(len(nolim), 5+1)
            self.assertEqual(extract(limit=2), nolim[:2])
            self.assertEqual(extract(limit=10), nolim)
            self.assertEqual(extract(limit=-2), nolim[-2:])
            self.assertEqual(extract(limit=-10), nolim)
            self.assertEqual(extract(limit=0), [])
            del sys.tracebacklimit
            self.assertEqual(extract(), nolim)
            sys.tracebacklimit = 2
            self.assertEqual(extract(), nolim[:2])
            self.assertEqual(extract(limit=3), nolim[:3])
            self.assertEqual(extract(limit=-3), nolim[-3:])
            sys.tracebacklimit = 0
            self.assertEqual(extract(), [])
            sys.tracebacklimit = -1
            self.assertEqual(extract(), [])

    def test_format_exception(self):
        try:
            self.last_raises5()
        except Exception:
            exc_type, exc_value, tb = sys.exc_info()
        # [1:-1] to exclude "Traceback (...)" header and
        # exception type and value
        def extract(**kwargs):
            return traceback.format_exception(exc_type, exc_value, tb, **kwargs)[1:-1]

        with support.swap_attr(sys, 'tracebacklimit', 1000):
            nolim = extract()
            self.assertEqual(len(nolim), 5+1)
            self.assertEqual(extract(limit=2), nolim[:2])
            self.assertEqual(extract(limit=10), nolim)
            self.assertEqual(extract(limit=-2), nolim[-2:])
            self.assertEqual(extract(limit=-10), nolim)
            self.assertEqual(extract(limit=0), [])
            del sys.tracebacklimit
            self.assertEqual(extract(), nolim)
            sys.tracebacklimit = 2
            self.assertEqual(extract(), nolim[:2])
            self.assertEqual(extract(limit=3), nolim[:3])
            self.assertEqual(extract(limit=-3), nolim[-3:])
            sys.tracebacklimit = 0
            self.assertEqual(extract(), [])
            sys.tracebacklimit = -1
            self.assertEqual(extract(), [])


class MiscTracebackCases(unittest.TestCase):
    #
    # Check non-printing functions in traceback module
    #

    def test_clear(self):
        def outer():
            middle()
        def middle():
            inner()
        def inner():
            i = 1
            1/0

        try:
            outer()
        except:
            type_, value, tb = sys.exc_info()

        # Initial assertion: there's one local in the inner frame.
        inner_frame = tb.tb_next.tb_next.tb_next.tb_frame
        self.assertEqual(len(inner_frame.f_locals), 1)

        # Clear traceback frames
        traceback.clear_frames(tb)

        # Local variable dict should now be empty.
        self.assertEqual(len(inner_frame.f_locals), 0)

    def test_extract_stack(self):
        def extract():
            return traceback.extract_stack()
        result = extract()
        lineno = extract.__code__.co_firstlineno
        self.assertEqual(result[-2:], [
            (__file__, lineno+2, 'test_extract_stack', 'result = extract()'),
            (__file__, lineno+1, 'extract', 'return traceback.extract_stack()'),
            ])


class TestFrame(unittest.TestCase):

    def test_basics(self):
        linecache.clearcache()
        linecache.lazycache("f", globals())
        f = traceback.FrameSummary("f", 1, "dummy")
        self.assertEqual(f,
            ("f", 1, "dummy", '"""Test cases for traceback module"""'))
        self.assertEqual(tuple(f),
            ("f", 1, "dummy", '"""Test cases for traceback module"""'))
        self.assertEqual(f, traceback.FrameSummary("f", 1, "dummy"))
        self.assertEqual(f, tuple(f))
        # Since tuple.__eq__ doesn't support FrameSummary, the equality
        # operator fallbacks to FrameSummary.__eq__.
        self.assertEqual(tuple(f), f)
        self.assertIsNone(f.locals)

    def test_lazy_lines(self):
        linecache.clearcache()
        f = traceback.FrameSummary("f", 1, "dummy", lookup_line=False)
        self.assertEqual(None, f._line)
        linecache.lazycache("f", globals())
        self.assertEqual(
            '"""Test cases for traceback module"""',
            f.line)

    def test_explicit_line(self):
        f = traceback.FrameSummary("f", 1, "dummy", line="line")
        self.assertEqual("line", f.line)


class TestStack(unittest.TestCase):

    def test_walk_stack(self):
        def deeper():
            return list(traceback.walk_stack(None))
        s1 = list(traceback.walk_stack(None))
        s2 = deeper()
        self.assertEqual(len(s2) - len(s1), 1)
        self.assertEqual(s2[1:], s1)

    def test_walk_tb(self):
        try:
            1/0
        except Exception:
            _, _, tb = sys.exc_info()
        s = list(traceback.walk_tb(tb))
        self.assertEqual(len(s), 1)

    def test_extract_stack(self):
        s = traceback.StackSummary.extract(traceback.walk_stack(None))
        self.assertIsInstance(s, traceback.StackSummary)

    def test_extract_stack_limit(self):
        s = traceback.StackSummary.extract(traceback.walk_stack(None), limit=5)
        self.assertEqual(len(s), 5)

    def test_extract_stack_lookup_lines(self):
        linecache.clearcache()
        linecache.updatecache('/foo.py', globals())
        c = test_code('/foo.py', 'method')
        f = test_frame(c, None, None)
        s = traceback.StackSummary.extract(iter([(f, 6)]), lookup_lines=True)
        linecache.clearcache()
        self.assertEqual(s[0].line, "import sys")

    def test_extract_stackup_deferred_lookup_lines(self):
        linecache.clearcache()
        c = test_code('/foo.py', 'method')
        f = test_frame(c, None, None)
        s = traceback.StackSummary.extract(iter([(f, 6)]), lookup_lines=False)
        self.assertEqual({}, linecache.cache)
        linecache.updatecache('/foo.py', globals())
        self.assertEqual(s[0].line, "import sys")

    def test_from_list(self):
        s = traceback.StackSummary.from_list([('foo.py', 1, 'fred', 'line')])
        self.assertEqual(
            ['  File "foo.py", line 1, in fred\n    line\n'],
            s.format())

    def test_from_list_edited_stack(self):
        s = traceback.StackSummary.from_list([('foo.py', 1, 'fred', 'line')])
        s[0] = ('foo.py', 2, 'fred', 'line')
        s2 = traceback.StackSummary.from_list(s)
        self.assertEqual(
            ['  File "foo.py", line 2, in fred\n    line\n'],
            s2.format())

    def test_format_smoke(self):
        # For detailed tests see the format_list tests, which consume the same
        # code.
        s = traceback.StackSummary.from_list([('foo.py', 1, 'fred', 'line')])
        self.assertEqual(
            ['  File "foo.py", line 1, in fred\n    line\n'],
            s.format())

    def test_locals(self):
        linecache.updatecache('/foo.py', globals())
        c = test_code('/foo.py', 'method')
        f = test_frame(c, globals(), {'something': 1})
        s = traceback.StackSummary.extract(iter([(f, 6)]), capture_locals=True)
        self.assertEqual(s[0].locals, {'something': '1'})

    def test_no_locals(self):
        linecache.updatecache('/foo.py', globals())
        c = test_code('/foo.py', 'method')
        f = test_frame(c, globals(), {'something': 1})
        s = traceback.StackSummary.extract(iter([(f, 6)]))
        self.assertEqual(s[0].locals, None)

    def test_format_locals(self):
        def some_inner(k, v):
            a = 1
            b = 2
            return traceback.StackSummary.extract(
                traceback.walk_stack(None), capture_locals=True, limit=1)
        s = some_inner(3, 4)
        self.assertEqual(
            ['  File "%s", line %d, in some_inner\n'
             '    traceback.walk_stack(None), capture_locals=True, limit=1)\n'
             '    a = 1\n'
             '    b = 2\n'
             '    k = 3\n'
             '    v = 4\n' % (__file__, some_inner.__code__.co_firstlineno + 4)
            ], s.format())

class TestTracebackException(unittest.TestCase):

    def test_smoke(self):
        try:
            1/0
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info)
            expected_stack = traceback.StackSummary.extract(
                traceback.walk_tb(exc_info[2]))
        self.assertEqual(None, exc.__cause__)
        self.assertEqual(None, exc.__context__)
        self.assertEqual(False, exc.__suppress_context__)
        self.assertEqual(expected_stack, exc.stack)
        self.assertEqual(exc_info[0], exc.exc_type)
        self.assertEqual(str(exc_info[1]), str(exc))

    def test_from_exception(self):
        # Check all the parameters are accepted.
        def foo():
            1/0
        try:
            foo()
        except Exception as e:
            exc_info = sys.exc_info()
            self.expected_stack = traceback.StackSummary.extract(
                traceback.walk_tb(exc_info[2]), limit=1, lookup_lines=False,
                capture_locals=True)
            self.exc = traceback.TracebackException.from_exception(
                e, limit=1, lookup_lines=False, capture_locals=True)
        expected_stack = self.expected_stack
        exc = self.exc
        self.assertEqual(None, exc.__cause__)
        self.assertEqual(None, exc.__context__)
        self.assertEqual(False, exc.__suppress_context__)
        self.assertEqual(expected_stack, exc.stack)
        self.assertEqual(exc_info[0], exc.exc_type)
        self.assertEqual(str(exc_info[1]), str(exc))

    def test_cause(self):
        try:
            try:
                1/0
            finally:
                exc_info_context = sys.exc_info()
                exc_context = traceback.TracebackException(*exc_info_context)
                cause = Exception("cause")
                raise Exception("uh oh") from cause
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info)
            expected_stack = traceback.StackSummary.extract(
                traceback.walk_tb(exc_info[2]))
        exc_cause = traceback.TracebackException(Exception, cause, None)
        self.assertEqual(exc_cause, exc.__cause__)
        self.assertEqual(exc_context, exc.__context__)
        self.assertEqual(True, exc.__suppress_context__)
        self.assertEqual(expected_stack, exc.stack)
        self.assertEqual(exc_info[0], exc.exc_type)
        self.assertEqual(str(exc_info[1]), str(exc))

    def test_context(self):
        try:
            try:
                1/0
            finally:
                exc_info_context = sys.exc_info()
                exc_context = traceback.TracebackException(*exc_info_context)
                raise Exception("uh oh")
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info)
            expected_stack = traceback.StackSummary.extract(
                traceback.walk_tb(exc_info[2]))
        self.assertEqual(None, exc.__cause__)
        self.assertEqual(exc_context, exc.__context__)
        self.assertEqual(False, exc.__suppress_context__)
        self.assertEqual(expected_stack, exc.stack)
        self.assertEqual(exc_info[0], exc.exc_type)
        self.assertEqual(str(exc_info[1]), str(exc))

    def test_unhashable(self):
        class UnhashableException(Exception):
            def __eq__(self, other):
                return True

        ex1 = UnhashableException('ex1')
        ex2 = UnhashableException('ex2')
        try:
            raise ex2 from ex1
        except UnhashableException:
            try:
                raise ex1
            except UnhashableException:
                exc_info = sys.exc_info()
        exc = traceback.TracebackException(*exc_info)
        formatted = list(exc.format())
        self.assertIn('UnhashableException: ex2\n', formatted[2])
        self.assertIn('UnhashableException: ex1\n', formatted[6])

    def test_limit(self):
        def recurse(n):
            if n:
                recurse(n-1)
            else:
                1/0
        try:
            recurse(10)
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info, limit=5)
            expected_stack = traceback.StackSummary.extract(
                traceback.walk_tb(exc_info[2]), limit=5)
        self.assertEqual(expected_stack, exc.stack)

    def test_lookup_lines(self):
        linecache.clearcache()
        e = Exception("uh oh")
        c = test_code('/foo.py', 'method')
        f = test_frame(c, None, None)
        tb = test_tb(f, 6, None)
        exc = traceback.TracebackException(Exception, e, tb, lookup_lines=False)
        self.assertEqual({}, linecache.cache)
        linecache.updatecache('/foo.py', globals())
        self.assertEqual(exc.stack[0].line, "import sys")

    def test_locals(self):
        linecache.updatecache('/foo.py', globals())
        e = Exception("uh oh")
        c = test_code('/foo.py', 'method')
        f = test_frame(c, globals(), {'something': 1, 'other': 'string'})
        tb = test_tb(f, 6, None)
        exc = traceback.TracebackException(
            Exception, e, tb, capture_locals=True)
        self.assertEqual(
            exc.stack[0].locals, {'something': '1', 'other': "'string'"})

    def test_no_locals(self):
        linecache.updatecache('/foo.py', globals())
        e = Exception("uh oh")
        c = test_code('/foo.py', 'method')
        f = test_frame(c, globals(), {'something': 1})
        tb = test_tb(f, 6, None)
        exc = traceback.TracebackException(Exception, e, tb)
        self.assertEqual(exc.stack[0].locals, None)

    def test_traceback_header(self):
        # do not print a traceback header if exc_traceback is None
        # see issue #24695
        exc = traceback.TracebackException(Exception, Exception("haven"), None)
        self.assertEqual(list(exc.format()), ["Exception: haven\n"])


class MiscTest(unittest.TestCase):

    def test_all(self):
        expected = set()
        blacklist = {'print_list'}
        for name in dir(traceback):
            if name.startswith('_') or name in blacklist:
                continue
            module_object = getattr(traceback, name)
            if getattr(module_object, '__module__', None) == 'traceback':
                expected.add(name)
        self.assertCountEqual(traceback.__all__, expected)


if __name__ == "__main__":
    unittest.main()