diff options
| -rw-r--r-- | Doc/library/traceback.rst | 10 | ||||
| -rw-r--r-- | Lib/test/test_traceback.py | 40 | ||||
| -rw-r--r-- | Lib/traceback.py | 25 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2021-01-13-12-55-41.bpo-42877.Fi1zEG.rst | 4 |
4 files changed, 69 insertions, 10 deletions
diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst index c233f18d30a..e938dd58b05 100644 --- a/Doc/library/traceback.rst +++ b/Doc/library/traceback.rst @@ -212,11 +212,16 @@ The module also defines the following classes: :class:`TracebackException` objects are created from actual exceptions to capture data for later printing in a lightweight fashion. -.. class:: TracebackException(exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False) +.. class:: TracebackException(exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False, compact=False) Capture an exception for later rendering. *limit*, *lookup_lines* and *capture_locals* are as for the :class:`StackSummary` class. + If *compact* is true, only data that is required by :class:`TracebackException`'s + ``format`` method is saved in the class attributes. In particular, the + ``__context__`` field is calculated only if ``__cause__`` is ``None`` and + ``__suppress_context__`` is false. + Note that when locals are captured, they are also shown in the traceback. .. attribute:: __cause__ @@ -294,6 +299,9 @@ capture data for later printing in a lightweight fashion. The message indicating which exception occurred is always the last string in the output. + .. versionchanged:: 3.10 + Added the *compact* parameter. + :class:`StackSummary` Objects ----------------------------- diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py index 07555a0411a..33bdda02666 100644 --- a/Lib/test/test_traceback.py +++ b/Lib/test/test_traceback.py @@ -1173,6 +1173,46 @@ class TestTracebackException(unittest.TestCase): 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 diff --git a/Lib/traceback.py b/Lib/traceback.py index aef37c9a7af..090465a3584 100644 --- a/Lib/traceback.py +++ b/Lib/traceback.py @@ -110,8 +110,8 @@ def print_exception(exc, /, value=_sentinel, tb=_sentinel, limit=None, \ value, tb = _parse_value_tb(exc, value, tb) if file is None: file = sys.stderr - for line in TracebackException( - type(value), value, tb, limit=limit).format(chain=chain): + te = TracebackException(type(value), value, tb, limit=limit, compact=True) + for line in te.format(chain=chain): print(line, file=file, end="") @@ -126,8 +126,8 @@ def format_exception(exc, /, value=_sentinel, tb=_sentinel, limit=None, \ printed as does print_exception(). """ value, tb = _parse_value_tb(exc, value, tb) - return list(TracebackException( - type(value), value, tb, limit=limit).format(chain=chain)) + te = TracebackException(type(value), value, tb, limit=limit, compact=True) + return list(te.format(chain=chain)) def format_exception_only(exc, /, value=_sentinel): @@ -146,8 +146,8 @@ def format_exception_only(exc, /, value=_sentinel): """ if value is _sentinel: value = exc - return list(TracebackException( - type(value), value, None).format_exception_only()) + te = TracebackException(type(value), value, None, compact=True) + return list(te.format_exception_only()) # -- not official API but folk probably use these two functions. @@ -476,7 +476,8 @@ class TracebackException: """ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None, - lookup_lines=True, capture_locals=False, _seen=None): + lookup_lines=True, capture_locals=False, compact=False, + _seen=None): # NB: we need to accept exc_traceback, exc_value, exc_traceback to # permit backwards compat with the existing API, otherwise we # need stub thunk objects just to glue it together. @@ -485,6 +486,7 @@ class TracebackException: if _seen is None: _seen = set() _seen.add(id(exc_value)) + # TODO: locals. self.stack = StackSummary.extract( walk_tb(exc_traceback), limit=limit, lookup_lines=lookup_lines, @@ -504,7 +506,7 @@ class TracebackException: if lookup_lines: self._load_lines() self.__suppress_context__ = \ - exc_value.__suppress_context__ if exc_value else False + exc_value.__suppress_context__ if exc_value is not None else False # Convert __cause__ and __context__ to `TracebackExceptions`s, use a # queue to avoid recursion (only the top-level call gets _seen == None) @@ -524,8 +526,13 @@ class TracebackException: _seen=_seen) else: cause = None + + if compact: + need_context = cause is None and not e.__suppress_context__ + else: + need_context = True if (e and e.__context__ is not None - and id(e.__context__) not in _seen): + and need_context and id(e.__context__) not in _seen): context = TracebackException( type(e.__context__), e.__context__, diff --git a/Misc/NEWS.d/next/Library/2021-01-13-12-55-41.bpo-42877.Fi1zEG.rst b/Misc/NEWS.d/next/Library/2021-01-13-12-55-41.bpo-42877.Fi1zEG.rst new file mode 100644 index 00000000000..49bb74bc536 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-01-13-12-55-41.bpo-42877.Fi1zEG.rst @@ -0,0 +1,4 @@ +Added the ``compact`` parameter to the constructor of +:class:`traceback.TracebackException` to reduce time and memory +for use cases that only need to call :func:`TracebackException.format` +and :func:`TracebackException.format_exception_only`. |