[1.0 backport] minimal implementation of dataclass_transform (#14523) #14532
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…ython#14523) This is a very simple first step to implementing [PEP 0681](https://peps.python.org/pep-0681/#decorator-function-example), which will allow MyPy to recognize user-defined types that behave similarly to dataclasses. This initial implementation is very limited: we only support decorator-style use of `typing.dataclass_transform` and do not support passing additional options to the transform (such as `freeze` or `init`). Within MyPy, we add a new `is_dataclass_transform` field to `FuncBase` which is populated during semantic analysis. When we check for plugin hooks later, we add new special cases to use the existing dataclasses plugin if a class decorator is marked with `is_dataclass_transform`. Ideally we would use a proper plugin API; the hacky special case here can be replaced in subsequent iterations. Co-authored-by: Wesley Wright <[email protected]>
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This is a very simple first step to implementing PEP 0681, which will allow MyPy to recognize user-defined types that behave similarly to dataclasses.
This initial implementation is very limited: we only support decorator-style use of
typing.dataclass_transformand do not support passing additional options to the transform (such asfreezeorinit).Within MyPy, we add a new
is_dataclass_transformfield toFuncBasewhich is populated during semantic analysis. When we check for plugin hooks later, we add new special cases to use the existing dataclasses plugin if a class decorator is marked withis_dataclass_transform. Ideally we would use a proper plugin API; the hacky special case here can be replaced in subsequent iterations.Co-authored-by: Wesley Wright [email protected]