[issue25108] traceback.extract_stack() compatibility break in 3.5

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Thank you Arfrever.

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Roundup Robot]

Roundup Robot added the comment:

New changeset 7e718bbf5152 by Serhiy Storchaka in branch '2.7':
Issue #25108: Fixed test_traceback in the case when this test is run twice.
https://hg.python.org/cpython/rev/7e718bbf5152

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Arfrever Frehtes Taifersar Arahesis]

Arfrever Frehtes Taifersar Arahesis added the comment:

> New changeset f6125114b55f by Serhiy Storchaka in branch '2.7':
> Issue #25108: Backported tests for traceback functions print_stack(),
> https://hg.python.org/cpython/rev/f6125114b55f

The new tests fail on 2.7 branch when Lib/test/test_traceback.pyc is present, 
because __file__ can contain path to *.pyc files in Python 2.
It is sufficient to run test_traceback twice to reproduce problem:

$ LD_LIBRARY_PATH="$(pwd)" ./python -m test.regrtest -v test_traceback
...
$ LD_LIBRARY_PATH="$(pwd)" ./python -m test.regrtest -v test_traceback
== CPython 2.7.10+ (2.7:fe84898fbe98, Sep 20 2015, 06:52:14) [GCC 4.9.3]
==   Linux-4.1.7 little-endian
==   /tmp/cpython/build/test_python_24845
Testing with flags: sys.flags(debug=0, py3k_warning=0, division_warning=0, 
division_new=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=0, 
no_user_site=0, no_site=0, ignore_environment=0, tabcheck=0, verbose=0, 
unicode=0, bytes_warning=0, hash_randomization=0)
[1/1] test_traceback
test_bad_indentation (test.test_traceback.TracebackCases) ... ok
test_base_exception (test.test_traceback.TracebackCases) ... ok
test_bug737473 (test.test_traceback.TracebackCases) ... ok
test_caret (test.test_traceback.TracebackCases) ... ok
test_format_exception_only_bad__str__ (test.test_traceback.TracebackCases) ... 
ok
test_nocaret (test.test_traceback.TracebackCases) ... ok
test_string_exception1 (test.test_traceback.TracebackCases) ... ok
test_string_exception2 (test.test_traceback.TracebackCases) ... ok
test_unicode (test.test_traceback.TracebackCases) ... ok
test_without_exception (test.test_traceback.TracebackCases) ... ok
test_format_stack (test.test_traceback.TracebackFormatTests) ... FAIL
test_print_stack (test.test_traceback.TracebackFormatTests) ... FAIL
test_traceback_format (test.test_traceback.TracebackFormatTests) ... ok
test_extract_stack (test.test_traceback.MiscTracebackCases) ... FAIL

==
FAIL: test_format_stack (test.test_traceback.TracebackFormatTests)
--
Traceback (most recent call last):
  File "/tmp/cpython/Lib/test/test_traceback.py", line 232, in test_format_stack
'return traceback.format_stack()\n' % (__file__, lineno+1),
AssertionError: Lists differ: ['  File "/tmp/cpython/Lib/tes... != ['  File 
"/tmp/cpython/Lib/tes...

First differing element 0:
  File "/tmp/cpython/Lib/test/test_traceback.py", line 226, in test_format_stack
result = fmt()

  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 226, in 
test_format_stack
result = fmt()


- ['  File "/tmp/cpython/Lib/test/test_traceback.py", line 226, in 
test_format_stack\nresult = fmt()\n',
+ ['  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 226, in 
test_format_stack\nresult = fmt()\n',
?  +

-  '  File "/tmp/cpython/Lib/test/test_traceback.py", line 225, in fmt\n
return traceback.format_stack()\n']
+  '  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 225, in fmt\n
return traceback.format_stack()\n']
?  +


==
FAIL: test_print_stack (test.test_traceback.TracebackFormatTests)
--
Traceback (most recent call last):
  File "/tmp/cpython/Lib/test/test_traceback.py", line 220, in test_print_stack
'traceback.print_stack()',
AssertionError: Lists differ: ['  File "/tmp/cpython/Lib/tes... != ['  File 
"/tmp/cpython/Lib/tes...

First differing element 0:
  File "/tmp/cpython/Lib/test/test_traceback.py", line 214, in test_print_stack
  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 214, in test_print_stack

- ['  File "/tmp/cpython/Lib/test/test_traceback.py", line 214, in 
test_print_stack',
+ ['  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 214, in 
test_print_stack',
?  +

   'prn()',
-  '  File "/tmp/cpython/Lib/test/test_traceback.py", line 212, in prn',
+  '  File "/tmp/cpython/Lib/test/test_traceback.pyc", line 212, in prn',
?  +

   'traceback.print_stack()']

==
FAIL: test_extract_stack (test.test_traceback.MiscTracebackCases)
--
Traceback (most recent call last):
  File "/tmp/cpython/Lib/test/test_traceback.py", line 248, in 
test_extract_stack
(__file__, lineno+1, 'extract', 'return traceback.extract_stack()'),
AssertionError: Lists differ: [('/tmp/cpython/Lib/test/test_... != 
[('/tmp/cpython/Lib/test/test_...

First differing element 0:
('/tmp/cpython/Lib/test/test_traceback.py', 244, 'test_extract_stack', 'result 
= 

[issue25108] traceback.extract_stack() compatibility break in 3.5

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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assignee:  -> serhiy.storchaka

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Roundup Robot]

Roundup Robot added the comment:

New changeset c9fb4362fb9f by Serhiy Storchaka in branch '3.5':
Issue #25108: Omitted internal frames in traceback functions print_stack(),
https://hg.python.org/cpython/rev/c9fb4362fb9f

New changeset 4e617566bcb6 by Serhiy Storchaka in branch 'default':
Issue #25108: Omitted internal frames in traceback functions print_stack(),
https://hg.python.org/cpython/rev/4e617566bcb6

New changeset 9f57c937958f by Serhiy Storchaka in branch '3.4':
Issue #25108: Backported tests for traceback functions print_stack(),
https://hg.python.org/cpython/rev/9f57c937958f

New changeset f6125114b55f by Serhiy Storchaka in branch '2.7':
Issue #25108: Backported tests for traceback functions print_stack(),
https://hg.python.org/cpython/rev/f6125114b55f

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nosy: +python-dev

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

> wouldn't changing walk_stack to add one more f_back be better?

print_stack and format_stack need to add two more f_backs.

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Here is a patch that restores compatibility. There were no tests for 
print_stack(), format_stack(), and extract_stack() without arguments. New tests 
are passed with 3.4.

There is a difference between this bug and warnings.warn(stacklevel=) at import 
time. In the latter the behavior is changed when we specify the stacklevel and 
we can't workaround this besides change the specified stacklevel depending on 
Python version. In the former the behavior is changed only when we don't 
specify a frame. The workaround is version independed: specify the frame 
explicitly. Therefore we will not break a code with a workaround for 3.5.0, but 
will fix a code without workaround.

--
keywords: +patch
nosy: +serhiy.storchaka
stage:  -> patch review
Added file: http://bugs.python.org/file40462/traceback_extract_stack.patch

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Nick Coghlan]

Nick Coghlan added the comment:

Serhiy's explanation and fix look good to me.

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Robert Collins]

Robert Collins added the comment:

wouldn't changing walk_stack to add one more f_back be better? Seems odd to 
work around it...

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Antoine Pitrou]

New submission from Antoine Pitrou:

This can be considered a regression, although perhaps it may not be desirable 
to fix it in a later release.

In 3.4:

>>> def f(): return traceback.extract_stack()
... 
>>> print([x[0:3] for x in f()])
[('', 1, ''), ('', 1, 'f')]

In 3.5:

>>> print([x[0:3] for x in f()])
[('', 1, ''), ('', 1, 'f'), 
('/home/antoine/35/lib/python3.5/traceback.py', 201, 'extract_stack')]

Note how the traceback module suddenly appears in the extracted stack. This 
breaks any application which uses a fixed offset into the returned stack to 
look up for information.

--
components: Library (Lib)
messages: 250649
nosy: larry, ncoghlan, pitrou, rbcollins
priority: normal
severity: normal
status: open
title: traceback.extract_stack() compatibility break in 3.5
type: behavior
versions: Python 3.5, Python 3.6

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Larry Hastings]

Larry Hastings added the comment:

Tracebacks aren't my forte, but this does smell like a regression and something 
that should be fixed.

My worry about things like this is that it isn't as much a "bug" as a "badly 
implemented interface".  As in, that's the interface in 3.5, and people will 
depend on it, and we change it in a point release at our peril.  (That's why I 
didn't permit "fixing" warnings.warn(stacklevel=) for 3.4.)

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Robert Collins]

Robert Collins added the comment:

Hmm, I think we can fix this. Its leaking due to the use of a helper I think. 
So - we should just fix this [and add a test, since clearly the test coverage 
is insufficient]

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[issue25108] traceback.extract_stack() compatibility break in 3.5

[Antoine Pitrou]

Antoine Pitrou added the comment:

Note the doc says "Extract the raw traceback from the current stack frame". The 
"current stack frame" may be assumed to be the caller's (as it is in previous 
Python releases).

Fortunately, this is also worked around by calling 
`extract_stack(sys._getframe())`.

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