Improve error handling for dataclass inheritance #13531
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This pull request: 1. Fixes python#8334. Overriding a dataclass attribute with a method or property now results in an error message, not a crash. (Overriding an attribute with a non-attribute at runtime will result in either inconsistent behavior or an exception, so I think unconditionally disallowing this is fine.) 2. Makes mypy report an error if you try subclassing a frozen dataclass with a non-frozen one or vice versa. Attempting to do this subclassing at runtime will raise a TypeError.
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I'm not too enthused about the new error message for (1) -- it's a bit cryptic imo. I'm open to bikeshedding there. |
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According to mypy_primer, this change has no effect on the checked open source code. |
JukkaL
approved these changes
Aug 27, 2022
Thanks for the PR! Looks good. The error message is a little cryptic, but I couldn't quickly think of a clearly better one. We can update the error message later if somebody comes up with a better idea.
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This pull request:
Fixes Crash when overriding field as property/method on frozen derived class #8334. Overriding a dataclass attribute with a method or property now results in an error message, not a crash.
(Overriding an attribute with a non-attribute at runtime will result in either inconsistent behavior or an exception, so I think unconditionally disallowing this is fine.)
Makes mypy report an error if you try subclassing a frozen dataclass with a non-frozen one or vice versa. Attempting to do this subclassing at runtime will raise a TypeError.