Lib/test/test_traceback.py

"""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 Error, captured_output, cpython_only, ALWAYS_EQ
from test.support.os_helper import TESTFN, unlink
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("+") + 1, 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("+") + 1, 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(")") + 1, err[2].find("^"))

        # No caret for "unexpected indent"
        err = self.get_exception_format(self.syntax_error_bad_indentation2,
                                        IndentationError)
        self.assertEqual(len(err), 3)
        self.assertEqual(err[1].strip(), "print(2)")

    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 sys, subprocess

        # 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)

    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")

    def test_print_exception_exc(self):
        output = StringIO()
        traceback.print_exception(Exception("projector"), file=output)
        self.assertEqual(output.getvalue(), "Exception: projector\n")

    def test_format_exception_exc(self):
        e = Exception("projector")
        output = traceback.format_exception(e)
        self.assertEqual(output, ["Exception: projector\n"])
        with self.assertRaisesRegex(ValueError, 'Both or neither'):
            traceback.format_exception(e.__class__, e)
        with self.assertRaisesRegex(ValueError, 'Both or neither'):
            traceback.format_exception(e.__class__, tb=e.__traceback__)
        with self.assertRaisesRegex(TypeError, 'positional-only'):
            traceback.format_exception(exc=e)

    def test_format_exception_only_exc(self):
        output = traceback.format_exception_only(Exception("projector"))
        self.assertEqual(output, ["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:
                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:
                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 7 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:
                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 7 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)

        # Check the boundary conditions. First, test just below the cutoff.
        with captured_output("stderr") as stderr_g:
            try:
                g(traceback._RECURSIVE_CUTOFF)
            except ValueError:
                render_exc()
            else:
                self.fail("no error raised")
        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'
            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+71}, in _check_recursive_traceback_display\n'
            '    g(traceback._RECURSIVE_CUTOFF)\n'
        )
        expected = (tb_line + result_g).splitlines()
        actual = stderr_g.getvalue().splitlines()
        self.assertEqual(actual, expected)

        # Second, test just above the cutoff.
        with captured_output("stderr") as stderr_g:
            try:
                g(traceback._RECURSIVE_CUTOFF + 1)
            except ValueError:
                render_exc()
            else:
                self.fail("no error raised")
        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 1 more time]\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+99}, in _check_recursive_traceback_display\n'
            '    g(traceback._RECURSIVE_CUTOFF + 1)\n'
        )
        expected = (tb_line + result_g).splitlines()
        actual = stderr_g.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_syntax_error_no_lineno(self):
        # See #34463.

        # Without filename
        e = SyntaxError('bad syntax')
        msg = self.get_report(e).splitlines()
        self.assertEqual(msg,
            ['SyntaxError: bad syntax'])
        e.lineno = 100
        msg = self.get_report(e).splitlines()
        self.assertEqual(msg,
            ['  File "<string>", line 100', 'SyntaxError: bad syntax'])

        # With filename
        e = SyntaxError('bad syntax')
        e.filename = 'myfile.py'

        msg = self.get_report(e).splitlines()
        self.assertEqual(msg,
            ['SyntaxError: bad syntax (myfile.py)'])
        e.lineno = 100
        msg = self.get_report(e).splitlines()
        self.assertEqual(msg,
            ['  File "myfile.py", line 100', 'SyntaxError: bad syntax'])

    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)

    def test_syntax_error_various_offsets(self):
        for offset in range(-5, 10):
            for add in [0, 2]:
                text = " "*add + "text%d" % offset
                expected = ['  File "file.py", line 1']
                if offset < 1:
                    expected.append("    %s" % text.lstrip())
                elif offset <= 6:
                    expected.append("    %s" % text.lstrip())
                    expected.append("    %s^" % (" "*(offset-1)))
                else:
                    expected.append("    %s" % text.lstrip())
                    expected.append("    %s^" % (" "*5))
                expected.append("SyntaxError: msg")
                expected.append("")
                err = self.get_report(SyntaxError("msg", ("file.py", 1, offset+add, text)))
                exp = "\n".join(expected)
                self.assertEqual(exp, 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()'),
            ])
        self.assertEqual(len(result[0]), 4)


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)
        self.assertNotEqual(f, object())
        self.assertEqual(f, ALWAYS_EQ)

    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)

    def test_len(self):
        f = traceback.FrameSummary("f", 1, "dummy", line="line")
        self.assertEqual(len(f), 4)


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'
             '    return traceback.StackSummary.extract(\n'
             '    a = 1\n'
             '    b = 2\n'
             '    k = 3\n'
             '    v = 4\n' % (__file__, some_inner.__code__.co_firstlineno + 3)
            ], 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_long_context_chain(self):
        def f():
            try:
                1/0
            except:
                f()

        try:
            f()
        except RecursionError:
            exc_info = sys.exc_info()
        else:
            self.fail("Exception not raised")

        te = traceback.TracebackException(*exc_info)
        res = list(te.format())

        # many ZeroDiv errors followed by the RecursionError
        self.assertGreater(len(res), sys.getrecursionlimit())
        self.assertGreater(
            len([l for l in res if 'ZeroDivisionError:' in l]),
            sys.getrecursionlimit() * 0.5)
        self.assertIn(
            "RecursionError: maximum recursion depth exceeded", res[-1])

    def test_compact_with_cause(self):
        try:
            try:
                1/0
            finally:
                cause = Exception("cause")
                raise Exception("uh oh") from cause
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info, compact=True)
            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(None, 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_compact_no_cause(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, compact=True)
            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_no_refs_to_exception_and_traceback_objects(self):
        try:
            1/0
        except Exception:
            exc_info = sys.exc_info()

        refcnt1 = sys.getrefcount(exc_info[1])
        refcnt2 = sys.getrefcount(exc_info[2])
        exc = traceback.TracebackException(*exc_info)
        self.assertEqual(sys.getrefcount(exc_info[1]), refcnt1)
        self.assertEqual(sys.getrefcount(exc_info[2]), refcnt2)

    def test_comparison_basic(self):
        try:
            1/0
        except Exception:
            exc_info = sys.exc_info()
            exc = traceback.TracebackException(*exc_info)
            exc2 = traceback.TracebackException(*exc_info)
        self.assertIsNot(exc, exc2)
        self.assertEqual(exc, exc2)
        self.assertNotEqual(exc, object())
        self.assertEqual(exc, ALWAYS_EQ)

    def test_comparison_params_variations(self):
        def raise_exc():
            try:
                raise ValueError('bad value')
            except:
                raise

        def raise_with_locals():
            x, y = 1, 2
            raise_exc()

        try:
            raise_with_locals()
        except Exception:
            exc_info = sys.exc_info()

        exc = traceback.TracebackException(*exc_info)
        exc1 = traceback.TracebackException(*exc_info, limit=10)
        exc2 = traceback.TracebackException(*exc_info, limit=2)

        self.assertEqual(exc, exc1)      # limit=10 gets all frames
        self.assertNotEqual(exc, exc2)   # limit=2 truncates the output

        # locals change the output
        exc3 = traceback.TracebackException(*exc_info, capture_locals=True)
        self.assertNotEqual(exc, exc3)

        # there are no locals in the innermost frame
        exc4 = traceback.TracebackException(*exc_info, limit=-1)
        exc5 = traceback.TracebackException(*exc_info, limit=-1, capture_locals=True)
        self.assertEqual(exc4, exc5)

        # there are locals in the next-to-innermost frame
        exc6 = traceback.TracebackException(*exc_info, limit=-2)
        exc7 = traceback.TracebackException(*exc_info, limit=-2, capture_locals=True)
        self.assertNotEqual(exc6, exc7)

    def test_comparison_equivalent_exceptions_are_equal(self):
        excs = []
        for _ in range(2):
            try:
                1/0
            except:
                excs.append(traceback.TracebackException(*sys.exc_info()))
        self.assertEqual(excs[0], excs[1])
        self.assertEqual(list(excs[0].format()), list(excs[1].format()))

    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()
        denylist = {'print_list'}
        for name in dir(traceback):
            if name.startswith('_') or name in denylist:
                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()