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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"warnings raised by test_peg_generator when setuptools_scm is installed","articleBody":"# Bug report\n\n### Bug description:\n\nHi, since #131802, we see `test_peg_generator` failing with the following warning:\n```\nWarning -- logging._handlerList was modified by test_peg_generator\nWarning --   Before: (140617884985088, [\u003cweakref at 0x7fe4271c8720; to 'logging._StderrHandler' at 0x7fe427ceb620\u003e, \u003cweakref at 0x7fe421d4d350; to 'setuptools_scm._log.AlwaysStdErrHandler' at 0x7fe420b25fd0\u003e], [\u003cweakref at 0x7fe4271c8720; to 'logging._StderrHandler' at 0x7fe427ceb620\u003e])\nWarning --   After:  (140617884985088, [\u003cweakref at 0x7fe4271c8720; to 'logging._StderrHandler' at 0x7fe427ceb620\u003e, \u003cweakref at 0x7fe421d4d350; to 'setuptools_scm._log.AlwaysStdErrHandler' at 0x7fe420b25fd0\u003e], [\u003cweakref at 0x7fe4271c8720; to 'logging._StderrHandler' at 0x7fe427ceb620\u003e, \u003cweakref at 0x7fe421d4d350; to 'setuptools_scm._log.AlwaysStdErrHandler' at 0x7fe420b25fd0\u003e])\n```\n\nFor some reason, during the execution, second reference to the same 'setuptools_scm._log.AlwaysStdErrHandler' appears in the `_handlerList`.\n\nWhen I remove `setuptools_scm`, the issue is gone.\n\nInterestingly (at least to me), when I revert changes done in #131802 in `lib/test/support/__init__.py` and `os_helper.py` (commenting out `import logging` is enough), the issue is gone as well, so it seems like some weird side effect of the import?\n\nI tried to track the issue and got through setuptools all the way to `ep.load()` in `finalize_options()` which triggers the issue (see trace below).\n\nI added some debug prints to `_addHandlerRef` function, and it's apparently called only once with this handler. Though I also see a single call for the `logging._StderrHandler'` and it's there twice as well, so I am probably overlooking something...\n\nHere is the trace from when the handler ref is being added during the test execution:\n```pytb\n.....\n  File \"/build/cpython-3.13/Lib/test/test_peg_generator/test_c_parser.py\", line 131, in build_extension\n    generate_parser_c_extension(grammar, Path('.'), library_dir=self.library_dir)\n  File \"/build/cpython-3.13/Tools/peg_generator/pegen/testutil.py\", line 107, in generate_parser_c_extension\n    compile_c_extension(\n  File \"/build/cpython-3.13/Tools/peg_generator/pegen/build.py\", line 160, in compile_c_extension\n    dist = Distribution({\"name\": extension_name, \"ext_modules\": [extension]})\n  File \"/usr/lib/python3.13/vendor-packages/setuptools/dist.py\", line 323, in __init__\n    _Distribution.__init__(self, dist_attrs)\n  File \"/usr/lib/python3.13/vendor-packages/setuptools/_distutils/dist.py\", line 309, in __init__\n    self.finalize_options()\n  File \"/usr/lib/python3.13/vendor-packages/setuptools/dist.py\", line 787, in finalize_options\n    for ep in sorted(loaded, key=by_order):\n  File \"/usr/lib/python3.13/vendor-packages/setuptools/dist.py\", line 786, in \u003clambda\u003e\n    loaded = map(lambda e: e.load(), filtered)\n  File \"/build/cpython-3.13/Lib/importlib/metadata/__init__.py\", line 179, in load\n    module = import_module(match.group('module'))\n  File \"/build/cpython-3.13/Lib/importlib/__init__.py\", line 88, in import_module\n    return _bootstrap._gcd_import(name[level:], package, level)\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1387, in _gcd_import\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1360, in _find_and_load\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1310, in _find_and_load_unlocked\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1387, in _gcd_import\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1360, in _find_and_load\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1310, in _find_and_load_unlocked\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1387, in _gcd_import\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1360, in _find_and_load\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1331, in _find_and_load_unlocked\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 935, in _load_unlocked\n  File \"\u003cfrozen importlib._bootstrap_external\u003e\", line 1026, in exec_module\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"/usr/lib/python3.13/vendor-packages/setuptools_scm/__init__.py\", line 8, in \u003cmodule\u003e\n    from ._config import DEFAULT_LOCAL_SCHEME\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1360, in _find_and_load\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1331, in _find_and_load_unlocked\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 935, in _load_unlocked\n  File \"\u003cfrozen importlib._bootstrap_external\u003e\", line 1026, in exec_module\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"/usr/lib/python3.13/vendor-packages/setuptools_scm/_config.py\", line 15, in \u003cmodule\u003e\n    from . import _log\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1415, in _handle_fromlist\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1360, in _find_and_load\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 1331, in _find_and_load_unlocked\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 935, in _load_unlocked\n  File \"\u003cfrozen importlib._bootstrap_external\u003e\", line 1026, in exec_module\n  File \"\u003cfrozen importlib._bootstrap\u003e\", line 488, in _call_with_frames_removed\n  File \"/usr/lib/python3.13/vendor-packages/setuptools_scm/_log.py\", line 48, in \u003cmodule\u003e\n    _default_handler = make_default_handler()\n  File \"/usr/lib/python3.13/vendor-packages/setuptools_scm/_log.py\", line 43, in make_default_handler\n    handler = AlwaysStdErrHandler()\n  File \"/usr/lib/python3.13/vendor-packages/setuptools_scm/_log.py\", line 23, in __init__\n    super().__init__(sys.stderr)\n  File \"/build/cpython-3.13/Lib/logging/__init__.py\", line 1128, in __init__\n    Handler.__init__(self)\n  File \"/build/cpython-3.13/Lib/logging/__init__.py\", line 941, in __init__\n    _addHandlerRef(self)\n```\n\nAll this is with Python 3.13 (latest changes), setuptools 80.3.1, setuptools_scm 8.3.1, and on Oracle Solaris, but I don't think this is necessarily platform dependent.\n\nI also reproduced this with older setuptools 73.0.1 and setuptools_scm 8.1.0.\n\n### CPython versions tested on:\n\n3.13\n\n### Operating systems tested on:\n\nOther","author":{"url":"https://github.com/kulikjak","@type":"Person","name":"kulikjak"},"datePublished":"2025-05-06T12:06:09.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":16},"url":"https://github.com/133509/cpython/issues/133509"}