gh-129605: Add more exception handling when computing suggestions in traceback.py by ADThomas-astro · Pull Request #129632 · python/cpython

ADThomas-astro · 2025-02-04T08:50:46Z

In _compute_suggestion_error in traceback.py, the code that handles AttributeError and ImportError is wrapped in try-excepts, but the code for NameError is not wrapped in a try-except. However, the hasattr(self, wrong_name) call fails if accessing an attribute raises an exception. This is what happens in the reproducer in the issue.

I wrapped the handling of NameError in a try-except to match the handling of the other two exception types.

I also added three related tests to test_traceback.py. All three of the new tests crash both PyREPL and the test_traceback.py test suite without the fix. The property test needed some creativity to trigger the bug and I'm a bit proud of it 😛

Let me know if the tests also need to be added to the PyREPL test suite.

Issue: traceback._compute_suggestion_error crashes on __getattr__ raising #129605

ghost · 2025-02-04T08:50:50Z

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bedevere-app · 2025-02-04T08:50:51Z

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danielhollas · 2025-02-04T10:31:41Z

        assert isinstance(exc_value, NameError)
-        # find most recent frame
-        if tb is None:
+        try:


This is a very broad try-except block. If you scoped it only around the hasattr call would the new test cases still pass?

Yes they would still pass. It's usually good practice to minimise code in a try block, but I think this is an exceptional case. This function attempts to provide "Did you mean foo?" suggestions after there has already been an error in user code. Hence a different exception propagating from this function is very unhelpful (and the cause of the issue). So I think it's worth having wider try blocks here to minimise the risk of unhandled exceptions in the future. The existing code has wide try blocks ignoring all Exception subclasses when doing processing for AttributeError (L1485-1494) and ImportError (L1499-1502). I think we we should treat the processing for NameError the same. (Although - I haven't found a way to cause an exception in L1508-1517, so this is mostly theoretical.) Happy to narrow the scope of the try if folks feel strongly.

github-actions · 2026-04-21T12:20:59Z

This PR is stale because it has been open for 30 days with no activity.

miss-islington-app · 2026-10-20T23:12:20Z

Thanks @ADThomas-astro for the PR, and @ambv for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15.
🐍🍒⛏🤖

miss-islington-app · 2026-10-20T23:12:29Z

Sorry, @ADThomas-astro and @ambv, I could not cleanly backport this to 3.14 due to a conflict.

Please backport manually with cherry_picker, see the devguide for more information.

cherry_picker 97b5f245136eb91bbc1aeddfcbf9bc571cedfdb5 3.14

bedevere-app · 2026-10-20T23:12:30Z

GH-159983 is a backport of this pull request to the 3.15 branch.

bedevere-bot · 2026-10-20T23:22:54Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86 Debian Installed with X 3.x (tierless) has failed when building commit 97b5f24.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1244/builds/9980) and take a look at the build logs.
Check if the failure is related to this commit (97b5f24) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1244/builds/9980

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/contextlib.py"�[0m, line �[35m116�[0m, in �[35minner�[0m
    return func(*args, **kwds)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m651�[0m, in �[35mtest_interrupt�[0m
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/contextlib.py"�[0m, line �[35m116�[0m, in �[35minner�[0m
    return func(*args, **kwds)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m632�[0m, in �[35m_kill_process�[0m
    self.assertEqual(�[31mjoin�[0m�[1;31m()�[0m, None)
                     �[31m~~~~�[0m�[1;31m^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m305�[0m, in �[35m__call__�[0m
    return �[31mself.func�[0m�[1;31m(*args, **kwds)�[0m
           �[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/process.py"�[0m, line �[35m156�[0m, in �[35mjoin�[0m
    res = self._popen.wait(timeout)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/popen_fork.py"�[0m, line �[35m44�[0m, in �[35mwait�[0m
    return �[31mself.poll�[0m�[1;31m(os.WNOHANG if timeout == 0.0 else 0)�[0m
           �[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/popen_fork.py"�[0m, line �[35m28�[0m, in �[35mpoll�[0m
    pid, sts = �[31mos.waitpid�[0m�[1;31m(self.pid, flag)�[0m
               �[31m~~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m628�[0m, in �[35mhandler�[0m
    raise RuntimeError('join took too long: %s' % p)
�[1;35mRuntimeError�[0m: �[35mjoin took too long: <Process name='Process-1' pid=3159 parent=3157 started daemon>�[0m


Traceback (most recent call last):
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/contextlib.py"�[0m, line �[35m116�[0m, in �[35minner�[0m
    return func(*args, **kwds)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m651�[0m, in �[35mtest_interrupt�[0m
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/contextlib.py"�[0m, line �[35m116�[0m, in �[35minner�[0m
    return func(*args, **kwds)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m632�[0m, in �[35m_kill_process�[0m
    self.assertEqual(�[31mjoin�[0m�[1;31m()�[0m, None)
                     �[31m~~~~�[0m�[1;31m^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m305�[0m, in �[35m__call__�[0m
    return �[31mself.func�[0m�[1;31m(*args, **kwds)�[0m
           �[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/process.py"�[0m, line �[35m156�[0m, in �[35mjoin�[0m
    res = self._popen.wait(timeout)
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/popen_fork.py"�[0m, line �[35m44�[0m, in �[35mwait�[0m
    return �[31mself.poll�[0m�[1;31m(os.WNOHANG if timeout == 0.0 else 0)�[0m
           �[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/multiprocessing/popen_fork.py"�[0m, line �[35m28�[0m, in �[35mpoll�[0m
    pid, sts = �[31mos.waitpid�[0m�[1;31m(self.pid, flag)�[0m
               �[31m~~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^�[0m
  File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.16/test/_test_multiprocessing.py"�[0m, line �[35m628�[0m, in �[35mhandler�[0m
    raise RuntimeError('join took too long: %s' % p)
�[1;35mRuntimeError�[0m: �[35mjoin took too long: <Process name='Process-170' pid=16764 parent=14673 started daemon>�[0m

bedevere-app · 2026-10-20T23:49:45Z

GH-159994 is a backport of this pull request to the 3.14 branch.

ambv · 2026-10-21T00:17:06Z

Pretty sure this PR is innocent of the "x86 Debian Installed with X 3.x" failure. Same commit, same machine, passed on "x86 Debian Non-Debug with X 3.x", build 9835 on the same worker (ware-debian-x86). It built the same 97b5f24 commit starting at 23:22:52 UTC, one second after the failing build finished. It passed, including test_multiprocessing_fork.test_processes.

…ons in traceback.py (GH-129632) (#159983) (cherry picked from commit 97b5f24) Co-authored-by: Adam D. Thomas <adamt@diversityarrays.com>

…ons in traceback.py (GH-129632) (#159994) (cherry picked from commit 97b5f24) Co-authored-by: Muse Code (Meta Muse Spark) Co-authored-by: Adam D. Thomas <adamt@diversityarrays.com>

bedevere-app Bot added the awaiting review label Feb 4, 2025

bedevere-app Bot mentioned this pull request Feb 4, 2025

traceback._compute_suggestion_error crashes on __getattr__ raising #129605

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danielhollas reviewed Feb 4, 2025

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github-actions Bot added the stale Stale PR or inactive for long period of time. label Apr 21, 2026

ADThomas-astro and others added 2 commits October 20, 2026 23:02

Add fix and tests

e93095c

📜🤖 Added by blurb_it.

97771ba

ambv force-pushed the gh129605_fix branch from 617c0b0 to 97771ba Compare October 20, 2026 21:03

ambv added needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Oct 20, 2026

ambv merged commit 97b5f24 into python:main Oct 20, 2026
57 checks passed

bedevere-app Bot removed the awaiting review label Oct 20, 2026

miss-islington-app Bot assigned ambv Oct 20, 2026

bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Oct 20, 2026

ambv mentioned this pull request Oct 20, 2026

[3.14] gh-129605: Add more exception handling when computing suggestions in traceback.py (GH-129632) #159994

Merged

bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Oct 20, 2026

ambv pushed a commit that referenced this pull request Oct 21, 2026

[3.15] gh-129605: Add more exception handling when computing suggesti…

9ce74c5

…ons in traceback.py (GH-129632) (#159983) (cherry picked from commit 97b5f24) Co-authored-by: Adam D. Thomas <adamt@diversityarrays.com>

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gh-129605: Add more exception handling when computing suggestions in traceback.py - #129632

gh-129605: Add more exception handling when computing suggestions in traceback.py#129632
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