René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Documented pattern for adding contextual information to LogRecord objects fails type checking","articleBody":"https://docs.python.org/3/library/logging.html#logrecord-objects gives the following pattern for adding contextual information to LogRecord objects which can then be used in log formats:\r\n\r\n```python\r\nold_factory = logging.getLogRecordFactory()\r\n\r\ndef record_factory(*args, **kwargs):\r\n    record = old_factory(*args, **kwargs)\r\n    record.custom_attribute = 0xdecafbad\r\n    return record\r\n\r\nlogging.setLogRecordFactory(record_factory)\r\n```\r\n\r\nHowever, if you use this pattern and run mypy, you'll get an error like `error: \"LogRecord\" has no attribute \"custom_attribute\"`. You can get around this error by using `setattr(record, \"custom_attribute\", 0xdecafbad)` instead of `record.custom_attribute = 0xdecafbad`.\r\n\r\nShould the stub for the `LogRecord` class define a `__setattr__` method because this sort of usage of assigning to arbitrary attributes is expected for the `LogRecord` class? Would that have undesirable side effects?\r\n\r\nHere is a complete example:\r\n\r\n```python\r\nimport logging\r\n\r\ncustom_contextual_data = \"XYZ\"\r\n\r\n\r\ndef main() -\u003e None:\r\n    logging.basicConfig(\r\n        format=\"[%(asctime)s] [%(custom_contextual_data)s] [%(name)s] %(levelname)s: %(message)s\", level=logging.DEBUG\r\n    )\r\n\r\n    old_factory = logging.getLogRecordFactory()\r\n\r\n    def record_factory(*args: object, **kwargs: object) -\u003e logging.LogRecord:\r\n        global custom_contextual_data\r\n        record = old_factory(*args, **kwargs)\r\n\r\n        # mypy: error: \"LogRecord\" has no attribute \"custom_contextual_data\"\r\n        record.custom_contextual_data = custom_contextual_data\r\n\r\n        # mypy: no error\r\n        # setattr(record, \"custom_contextual_data\", custom_contextual_data)\r\n\r\n        return record\r\n\r\n    logging.setLogRecordFactory(record_factory)\r\n\r\n    logger = logging.getLogger(__name__)\r\n    logger.info(\"Hello XYZ world!\")\r\n    global custom_contextual_data\r\n    custom_contextual_data = \"ABC\"\r\n    logger.info(\"Hello ABC world!\")\r\n\r\n\r\nif __name__ == \"__main__\":\r\n    main()\r\n```\r\n\r\nmypy.ini:\r\n\r\n```\r\n[mypy]\r\nfiles = mypy_log_record_repro/\r\nstrict_equality = True\r\ndisallow_untyped_defs = True\r\ndisallow_untyped_calls = True\r\ndisallow_untyped_decorators = True\r\nno_implicit_optional = True\r\nstrict_optional = True\r\nwarn_unused_ignores = True\r\nwarn_redundant_casts = True\r\nwarn_no_return = True\r\nwarn_return_any = True\r\nwarn_unreachable = True\r\n```","author":{"url":"https://github.com/LHCGreg","@type":"Person","name":"LHCGreg"},"datePublished":"2022-05-12T15:31:29.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/7833/typeshed/issues/7833"}