{"record":{"id":"1cad98527a6b38c9","repo":"reflex-dev/reflex","slug":"rx-memo-does-not-support-positional-only-parame","errorCode":null,"errorMessage":"`@rx.memo` does not support positional-only parameters in `{fn_name}`.","messagePattern":"`@rx\\.memo` does not support positional-only parameters in `(.+?)`\\.","errorType":"exception","errorClass":"TypeError","httpStatus":null,"severity":"error","filePath":"packages/reflex-base/src/reflex_base/components/memo.py","lineNumber":1365,"sourceCode":"    \"\"\"Reject Python parameter kinds (``*args`` / ``**kwargs`` / positional-only)\n    that memo does not support.\n\n    Args:\n        parameter: The parameter to check.\n        fn_name: The function name for error messages.\n\n    Raises:\n        TypeError: If the parameter uses an unsupported kind.\n    \"\"\"\n    if parameter.kind is inspect.Parameter.VAR_POSITIONAL:\n        msg = f\"`@rx.memo` does not support `*args` in `{fn_name}`.\"\n        raise TypeError(msg)\n    if parameter.kind is inspect.Parameter.VAR_KEYWORD:\n        msg = f\"`@rx.memo` does not support `**kwargs` in `{fn_name}`.\"\n        raise TypeError(msg)\n    if parameter.kind is inspect.Parameter.POSITIONAL_ONLY:\n        msg = f\"`@rx.memo` does not support positional-only parameters in `{fn_name}`.\"\n        raise TypeError(msg)\n\n\ndef _classify_parameter(\n    annotation: Any, param_name: str, fn_name: str\n) -> tuple[MemoParamKind, Any]:\n    \"\"\"Walk ``_CLASSIFICATION_ORDER`` and return the first matching kind.\n\n    Args:\n        annotation: The parameter annotation.\n        param_name: The parameter name (some kinds care, e.g. ``children``).\n        fn_name: The function name for error messages.\n\n    Returns:\n        The matched ``(kind, kind_data)``.\n\n    Raises:\n        TypeError: If no kind matches.\n    \"\"\"","sourceCodeStart":1347,"sourceCodeEnd":1383,"githubUrl":"https://github.com/reflex-dev/reflex/blob/45b8ed5ab735f8a56bbb09a42384f030eb0208e7/packages/reflex-base/src/reflex_base/components/memo.py#L1347-L1383","documentation":"`@rx.memo` rejects positional-only parameters (those before a `/` in the signature). Memo props are always passed by keyword at the call site, and positional-only names cannot participate in that binding convention, so the signature is rejected at decoration time.","triggerScenarios":"Decorating a function with `@rx.memo` that uses the `/` positional-only marker, e.g. `@rx.memo def item(x, /, y: rx.Var[str]): ...`, or a lambda/function defined via `inspect` or C extensions with implicit positional-only args.","commonSituations":"Copying modern Python API signatures that use `/`; using `functools.partial` or wrappers that surface parameters as positional-only; mixing conventions when porting typed APIs into memo components.","solutions":["Remove the `/` marker so all parameters are normal positional-or-keyword parameters.","Annotate each parameter as `rx.Var[...]` or `rx.RestProp` and pass props by keyword when calling the memo."],"exampleFix":"# before\n@rx.memo\ndef item(value, /):\n    return rx.text(value)\n\n# after\n@rx.memo\ndef item(value: rx.Var[str]):\n    return rx.text(value)","handlingStrategy":"validation","validationCode":"import inspect\n\ndef memo_signature_ok(fn) -> bool:\n    return all(\n        p.kind is not inspect.Parameter.POSITIONAL_ONLY\n        for p in inspect.signature(fn).parameters.values()\n    )","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Never use the `/` positional-only marker in memo signatures.","Write memo params as ordinary positional-or-keyword parameters annotated with rx.Var[...]."],"tags":["reflex","memo","positional-only","signature","typeerror"],"backgroundTag":"unsupported-function-signature","analyzedSha":"45b8ed5ab735f8a56bbb09a42384f030eb0208e7","analyzedAt":"2026-08-28T19:25:27.644Z","schemaVersion":2},"datasetVersion":"2026-08-28T21:17:43.275Z"}