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bpo-45171: Fix stacklevel handling in logging. (GH-28287) #28287

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Merged
merged 1 commit into from
Mar 27, 2022
Merged

bpo-45171: Fix stacklevel handling in logging. (GH-28287) #28287

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67 changes: 35 additions & 32 deletions Lib/logging/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,8 +159,8 @@ def addLevelName(level, levelName):
finally:
_releaseLock()

if hasattr(sys, '_getframe'):
currentframe = lambda: sys._getframe(3)
if hasattr(sys, "_getframe"):
currentframe = lambda: sys._getframe(1)
else: #pragma: no cover
def currentframe():
"""Return the frame object for the caller's stack frame."""
Expand All @@ -184,13 +184,18 @@ def currentframe():
_srcfile = os.path.normcase(addLevelName.__code__.co_filename)

# _srcfile is only used in conjunction with sys._getframe().
# To provide compatibility with older versions of Python, set _srcfile
# to None if _getframe() is not available; this value will prevent
# findCaller() from being called. You can also do this if you want to avoid
# the overhead of fetching caller information, even when _getframe() is
# available.
#if not hasattr(sys, '_getframe'):
# _srcfile = None
# Setting _srcfile to None will prevent findCaller() from being called. This
# way, you can avoid the overhead of fetching caller information.

# The following is based on warnings._is_internal_frame. It makes sure that
# frames of the import mechanism are skipped when logging at module level and
# using a stacklevel value greater than one.
def _is_internal_frame(frame):
"""Signal whether the frame is a CPython or logging module internal."""
filename = os.path.normcase(frame.f_code.co_filename)
return filename == _srcfile or (
"importlib" in filename and "_bootstrap" in filename
)


def _checkLevel(level):
Expand Down Expand Up @@ -1558,33 +1563,31 @@ def findCaller(self, stack_info=False, stacklevel=1):
f = currentframe()
#On some versions of IronPython, currentframe() returns None if
#IronPython isn't run with -X:Frames.
if f is not None:
f = f.f_back
orig_f = f
while f and stacklevel > 1:
f = f.f_back
stacklevel -= 1
if not f:
f = orig_f
rv = "(unknown file)", 0, "(unknown function)", None
while hasattr(f, "f_code"):
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Note that the new code doesn't verify that frame object contain an f_code attribute. It does verify that the frame object is not None. The f_code attribute is prescribed by the CPython data model and the warnings module doesn't check for it's presence either (it does check for stack exhaustion/None, like the new code here).

co = f.f_code
filename = os.path.normcase(co.co_filename)
if filename == _srcfile:
f = f.f_back
continue
sinfo = None
if stack_info:
sio = io.StringIO()
sio.write('Stack (most recent call last):\n')
if f is None:
return "(unknown file)", 0, "(unknown function)", None
while stacklevel > 0:
next_f = f.f_back
if next_f is None:
##TODO: We've got options here
## If we want to use the last (deepest) frame:
break
## If we want to mimic the warnings module:
#return ("sys", 1, "(unknown function)", None)
## If we want to be pedantic:
#raise ValueError("call stack is not deep enough")
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So far, findCaller did not throw, so to keep the more backward-compatible I think it would be better if it did not throw.

Comment on lines +1570 to +1577
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@vsajip Thanks for the approval and merge! Note that there was a TODO here which I summarized in the original PR description as:

Regarding the last point, I did not know what to do in case more frames are to be skipped than the height of the stack. I listed three possibilities in the code which I think would all be sensible.

Having it merged like this is not wrong per se (it will use the deepest available frame if the stack is exhausted), but it would be good to at least remove the TODO: part on line 1571. Maybe all of the above could even be replaced with

            if next_f is None:
                # Not enough stack frames. We use the last (deepest) one.
                break

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Or maybe leave it as a reminder in case this needs revisiting for any reason?

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Indeed, but in that case I would still remove the word TODO:, since nothing needs to be done.

Anyway, I really appreciate that you took a look at this PR. Thanks!

f = next_f
if not _is_internal_frame(f):
stacklevel -= 1
co = f.f_code
sinfo = None
if stack_info:
with io.StringIO() as sio:
sio.write("Stack (most recent call last):\n")
traceback.print_stack(f, file=sio)
sinfo = sio.getvalue()
if sinfo[-1] == '\n':
sinfo = sinfo[:-1]
sio.close()
rv = (co.co_filename, f.f_lineno, co.co_name, sinfo)
break
return rv
return co.co_filename, f.f_lineno, co.co_name, sinfo

def makeRecord(self, name, level, fn, lno, msg, args, exc_info,
func=None, extra=None, sinfo=None):
Expand Down
13 changes: 12 additions & 1 deletion Lib/test/test_logging.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4997,9 +4997,10 @@ def test_find_caller_with_stack_info(self):

def test_find_caller_with_stacklevel(self):
the_level = 1
trigger = self.logger.warning

def innermost():
self.logger.warning('test', stacklevel=the_level)
trigger('test', stacklevel=the_level)

def inner():
innermost()
Expand All @@ -5021,6 +5022,16 @@ def outer():
self.assertEqual(records[-1].funcName, 'outer')
self.assertGreater(records[-1].lineno, lineno)
lineno = records[-1].lineno
trigger = self.logger.warn
outer()
self.assertEqual(records[-1].funcName, 'outer')
root_logger = logging.getLogger()
root_logger.addHandler(self.recording)
trigger = logging.warning
outer()
self.assertEqual(records[-1].funcName, 'outer')
root_logger.removeHandler(self.recording)
trigger = self.logger.warning
the_level += 1
outer()
self.assertEqual(records[-1].funcName, 'test_find_caller_with_stacklevel')
Expand Down
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2021-09-11-16-06-54.bpo-45171.ec597j.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix handling of the ``stacklevel`` argument to logging functions in the
:mod:`logging` module so that it is consistent accross all logging functions
and, as advertised, similar to the ``stacklevel`` argument used in
:meth:`~warnings.warn`.