[dataclass_transform] include __dataclass_fields__ in transformed types #14752
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…lass transform types
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
JukkaL
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Feb 22, 2023
| # | ||
| # In either case, we're aiming to match the Typeshed stub for `is_dataclass`, which expects | ||
| # the instance to have a `__dataclass_fields__` attribute of type `dict[str, Field[Any]]`. | ||
| if self._spec is _TRANSFORM_SPEC_FOR_DATACLASSES: |
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The is check probably doesn't work in incremental mode, when the spec has been deserialized. Another way to do this would be to add an internal boolean flag to the spec that is only true for regular dataclasses.
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I believe it shouldn't hit any serialization issues because _TRANSFORM_SPEC_FOR_DATACLASSES is never actually attached to an AST node; we return it from another function in this plugin here when we fail to find a spec in the AST.
That said, it's definitely opaque and not very elegant; I should probably make a helper function or something similar at least
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JukkaL
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Feb 23, 2023
cdce8p
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…transformed types (python#14752) `dataclasses` uses a `__dataclass_fields__` attribute on each class to mark that it is a dataclass, and Typeshed checks for this attribute in its stubs for functions like `dataclasses.is_dataclass` and `dataclasses.asdict`. In python#14667, I mistakenly removed this attribute for classes transformed by a `dataclass_transform`. This was due to a misinterpretation of PEP 681 on my part; after rereading the [section on dataclass semantics](https://peps.python.org/pep-0681/#dataclass-semantics), it says: > Except where stated otherwise in this PEP, classes impacted by `dataclass_transform`, either by inheriting from a class that is decorated with `dataclass_transform` or by being decorated with a function decorated with `dataclass_transform`, are assumed to behave like stdlib dataclass. The PEP doesn't seem to state anything about `__dataclass_fields__` or the related functions as far as I can tell, so we should assume that transforms should match the behavior of `dataclasses.dataclass` in this regard and include the attribute. This also matches the behavior of Pyright, which the PEP defines as the reference implementation. (cherry picked from commit 54635de)
hauntsaninja
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…transformed types (#14752) (#14769) `dataclasses` uses a `__dataclass_fields__` attribute on each class to mark that it is a dataclass, and Typeshed checks for this attribute in its stubs for functions like `dataclasses.is_dataclass` and `dataclasses.asdict`. In #14667, I mistakenly removed this attribute for classes transformed by a `dataclass_transform`. This was due to a misinterpretation of PEP 681 on my part; after rereading the [section on dataclass semantics](https://peps.python.org/pep-0681/#dataclass-semantics), it says: > Except where stated otherwise in this PEP, classes impacted by `dataclass_transform`, either by inheriting from a class that is decorated with `dataclass_transform` or by being decorated with a function decorated with `dataclass_transform`, are assumed to behave like stdlib dataclass. The PEP doesn't seem to state anything about `__dataclass_fields__` or the related functions as far as I can tell, so we should assume that transforms should match the behavior of `dataclasses.dataclass` in this regard and include the attribute. This also matches the behavior of Pyright, which the PEP defines as the reference implementation. (cherry picked from commit 54635de) Co-authored-by: Wesley Collin Wright <[email protected]>
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dataclassesuses a__dataclass_fields__attribute on each class to mark that it is a dataclass, and Typeshed checks for this attribute in its stubs for functions likedataclasses.is_dataclassanddataclasses.asdict.In #14667, I mistakenly removed this attribute for classes transformed by a
dataclass_transform. This was due to a misinterpretation of PEP 681 on my part; after rereading the section on dataclass semantics, it says:The PEP doesn't seem to state anything about
__dataclass_fields__or the related functions as far as I can tell, so we should assume that transforms should match the behavior ofdataclasses.dataclassin this regard and include the attribute. This also matches the behavior of Pyright, which the PEP defines as the reference implementation.