test_traceback: test_import_from_error_bad_suggestions_do_not_trigger_for_small_names() fails randomly on "wasm32-emscripten node (dynamic linking)" buildbot

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test_traceback: test_import_from_error_bad_suggestions_do_not_trigger_for_small_names() fails randomly on the "wasm32-emscripten node (dynamic linking)" buildbot worker.

Example: https://buildbot.python.org/all/#/builders/1056/builds/928

FAIL: test_import_from_error_bad_suggestions_do_not_trigger_for_small_names (test.test_traceback.CPythonSuggestionFormattingTests.test_import_from_error_bad_suggestions_do_not_trigger_for_small_names) (name='b')
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Traceback (most recent call last):
  File "/opt/buildbot/bcannon-wasm/3.x.bcannon-wasm.emscripten-node-dl/build/Lib/test/test_traceback.py", line 3173, in test_import_from_error_bad_suggestions_do_not_trigger_for_small_names
    self.assertNotIn("mom", actual)
AssertionError: 'mom' unexpectedly found in "ImportError: cannot import name 'b' from 'IMwPxQRPpcEcmomu' (/tmp/tmpanzezi5a/IMwPxQRPpcEcmomu.py)"

cc @brettcannon @tiran @pablogsal

Linked PRs

• gh-99894: Ensure the local names don't collide with the test file in traceback suggestion error checking #99895

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Other failures:

• 6 days ago: s390x RHEL7 LTO 3.x: https://buildbot.python.org/all/#/builders/402/builds/3434
• 6 days ago: wasm32-wasi 3.x: https://buildbot.python.org/all/#builders/1046/builds/954
• 16 days ago: PPC64LE Fedora Stable 3.x: https://buildbot.python.org/all/#/builders/90/builds/2415
• 1 month ago: wasm32-emscripten node (pthreads) 3.x: https://buildbot.python.org/all/#builders/1050/builds/720

[pablogsal]

On it

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I'm able to reproduce the issue on my x86-64 Fedora 37:

$ ./python -m test test_traceback -j20 -F -m test_import_from_error_bad_suggestions_do_not_trigger_for_small_names -v
(...)
0:00:08 load avg: 22.67 [ 56/1] test_traceback failed (1 failure)
test_import_from_error_bad_suggestions_do_not_trigger_for_small_names (test.test_traceback.CPythonSuggestionFormattingTests.test_import_from_error_bad_suggestions_do_not_trigger_for_small_names) ... 
  test_import_from_error_bad_suggestions_do_not_trigger_for_small_names (test.test_traceback.CPythonSuggestionFormattingTests.test_import_from_error_bad_suggestions_do_not_trigger_for_small_names) (name='py') ... FAIL
test_import_from_error_bad_suggestions_do_not_trigger_for_small_names (test.test_traceback.PurePythonSuggestionFormattingTests.test_import_from_error_bad_suggestions_do_not_trigger_for_small_names) ... ok

======================================================================
FAIL: test_import_from_error_bad_suggestions_do_not_trigger_for_small_names (test.test_traceback.CPythonSuggestionFormattingTests.test_import_from_error_bad_suggestions_do_not_trigger_for_small_names) (name='py')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/test/test_traceback.py", line 3173, in test_import_from_error_bad_suggestions_do_not_trigger_for_small_names
    self.assertNotIn("mom", actual)
AssertionError: 'mom' unexpectedly found in "ImportError: cannot import name 'py' from 'bGamirGQRkOmsncE' (/tmp/test_python_f0fe4pnw/tmpzmomru6k/bGamirGQRkOmsncE.py)"

----------------------------------------------------------------------
Ran 2 tests in 0.273s
(...)
Total duration: 9.0 sec
Tests result: FAILURE

EDIT: Oh I forgot that to trigger the bug, I had to stress my machine by running ./python -m test -j4 -F in a different terminal. My laptop has 6 CPU cores (12 threads).

[pablogsal]

I made a PR for this

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LoooooooL, I think that I understood the issue 😄 Funny one.

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On main, I can reproduce the issue quickly with commands that I gave in a previous comment:

• 9 seconds: 'mom' unexpectedly found
• 24 seconds: 'vvv' unexpectedly found
• 10 seconds: 'vvv' unexpectedly found
• 1 min 17 sec: 'mom' unexpectedly found

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Fixed by 0563be2