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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Misbehavior of `f.__code__.co_firstlineno` for decorated functions","articleBody":"# Bug report\n\n### Bug description:\n\nSee also: #139783\n\nCompare:\n\n```py\ndummy = lambda f: f                 # L1\n@dummy                              # L2\ndef f():                            # L3\n    return                          # L4\nprint(f.__code__.co_firstlineno)    # L5  # result = 2\n```\n\nwith\n\n```py\ndummy = lambda f: f                 # L1\npass                                # L2\ndef f():                            # L3\n    return                          # L4\nprint(f.__code__.co_firstlineno)    # L5  # result = 3\n```\n\nand\n\n```py\ndummy = lambda f: f                 # L1\n@\\\ndummy                               # L3\ndef f():                            # L4\n    return                          # L5\nprint(f.__code__.co_firstlineno)    # L6  # result = 3\n```\n\nIn the last example, the line continuation after `@` is not handled correctly and the first line for `f.__code__` then becomes the line at dummy. Because of that, the values returned by `inspect.findsource(f)` will not be consistent and `inspect.getsourcelines` will not use the correct source (it will only start at \"dummy\" and will not contain the \"@\\\" part).\n\n@serhiy-storchaka suggested that this is an issue in the AST parser. I however don't know how we should actually fix this.\n\n### Consequences to `inspect.getsource` and other introspection functions:\n\n```python\nimport inspect\n\ndef outer(*args, **kwargs):\n    def inner(f):\n        return f\n    return deco\n\n@(\n    outer(\n        ...\n    )\n)\ndef f():\n    return \"hello\"\n\nprint(inspect.getsource(f))\n```\n\nOn Python 3.12, the output is expected:\n\n```py\n@(\n    outer(\n        ...\n    )\n)\ndef func():\n    return \"hello\"\n```\n\nOn Python 3.13.7, the output is missing the first line `@(`:\n\n```py\n    outer(\n        ...\n    )\n)\ndef func():\n    return \"hello\"\n```\n\nOn Python 3.13.9 and `main`, we are missing `@` and outer parentheses:\n\n```py\n    outer(\n        ...\n    )\n```\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\n_No response_","author":{"url":"https://github.com/picnixz","@type":"Person","name":"picnixz"},"datePublished":"2025-10-09T11:13:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/139838/cpython/issues/139838"}