[Python-checkins] bpo-42877: add the 'compact' param to TracebackException's __init__ (#24179)
gvanrossum
webhook-mailer at python.org
Thu Jan 14 21:45:15 EST 2021
https://github.com/python/cpython/commit/4c94d74152a511d977fe26a4f3a32b7352ba9024
commit: 4c94d74152a511d977fe26a4f3a32b7352ba9024
branch: master
author: Irit Katriel <iritkatriel at yahoo.com>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2021-01-14T18:45:02-08:00
summary:
bpo-42877: add the 'compact' param to TracebackException's __init__ (#24179)
Use it to reduce the time and memory taken up by several of traceback's module-level functions.
files:
A Misc/NEWS.d/next/Library/2021-01-13-12-55-41.bpo-42877.Fi1zEG.rst
M Doc/library/traceback.rst
M Lib/test/test_traceback.py
M Lib/traceback.py
diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst
index c233f18d30a29..e938dd58b0531 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 07555a0411a08..33bdda026662c 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -1173,6 +1173,46 @@ def f():
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 aef37c9a7af68..090465a3584b7 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 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
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 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
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 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
_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 0000000000000..49bb74bc53665
--- /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`.
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