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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[1.20 regression] reachability in django-modern-rest","articleBody":"Hi!\n\nI am facing 150+ errors in my project https://github.com/wemake-services/django-modern-rest after updating mypy to `1.20` from `1.19.`\n\nHere are the most frequest ones:\n\n## lru_cache issues\n\n```\ndmr/response.py:236: error: Cannot determine type of \"resolve_setting\"  [has-type]\ndmr/response.py:236: note: Revealed type is \"Any\"\ndmr/response.py:237: error: Cannot determine type of \"resolve_setting\"  [has-type]\ndmr/routing.py:108: error: Cannot determine type of \"resolve_setting\"  [has-type]\ndmr/routing.py:190: error: Cannot determine type of \"resolve_setting\"  [has-type]\ndmr/parsers.py:232: error: Cannot determine type of \"resolve_setting\"  [has-type]\ndmr/parsers.py:284: error: Cannot determine type of \"resolve_setting\"  [has-type]\n```\n\nFor some reason all code that is using [`resolve_setting`](https://github.com/wemake-services/django-modern-rest/blob/9062072376962f8b9ba6e195244ca702fe3d15e8/dmr/routing.py#L107-L109) fails with this error:\n\n```python\nrenderers_list = (\n    resolve_setting(Settings.renderers) if renderers is None else renderers\n)\n```\n\nHere's how [it is defined](https://github.com/wemake-services/django-modern-rest/blob/9062072376962f8b9ba6e195244ca702fe3d15e8/dmr/settings.py#L168):\n\n```python\n@lru_cache(maxsize=MAX_CACHE_SIZE)\ndef resolve_setting(\n    setting_name: Settings,\n    *,\n    import_string: bool = False,\n) -\u003e Any:\n    \"\"\"\n    Resolves setting by *setting_name*.\n\n    The result is cached using ``@lru_cache`` for performance.\n    When testing with custom settings, you *must* call\n    :func:`clear_settings_cache` before and after modifying\n    Django settings to ensure the cache is invalidated properly.\n    \"\"\"\n    setting = _resolve_defaults().get(\n        setting_name,\n        _DEFAULTS[setting_name],\n    )\n    if import_string and isinstance(setting, str):\n        return module_loading.import_string(setting)\n    return setting  # pyright: ignore[reportUnknownVariableType]\n```\n\nMaybe `@lru_cache(maxsize=MAX_CACHE_SIZE)` is the root cause? If I remove this decorator - all errors are gone.\n\nWe also faced a similiar problem in our `django-stubs` PR: https://github.com/typeddjango/django-stubs/pull/3252#discussion_r3018408038\n\n## Unreachable\n\nI have more than 120+ errors that some statements are unreachable.\nExamples:\n\n```\n(.venv) ~/Desktop/django-modern-rest  master ✗                                         1 ⚠️\n» mypy dmr\ndmr/settings.py:122: error: Statement is unreachable  [unreachable]\ndmr/validation/settings.py:41: error: Statement is unreachable  [unreachable]\n```\n\n1. https://github.com/wemake-services/django-modern-rest/blob/9062072376962f8b9ba6e195244ca702fe3d15e8/dmr/settings.py#L122\n2. https://github.com/wemake-services/django-modern-rest/blob/9062072376962f8b9ba6e195244ca702fe3d15e8/dmr/validation/settings.py#L41\n\nThese are two different module-level definitions. Not sure what is the root cause here :(\n","author":{"url":"https://github.com/sobolevn","@type":"Person","name":"sobolevn"},"datePublished":"2026-04-01T08:51:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/21132/mypy/issues/21132"}