Make BaseDescriptor generic wrt the owning class #254
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Previously, BaseDescriptor typed the owning object as `Thing`, which was a bit loose and led to some vague type hints (particularly for functional properties and actions). I've added a second generic parameter for the owning class. This makes some of the type test code a bit more verbose, but it gets rid of a fair few `type: ignore` statements and also means we now detect a few type errors that were previously missed. This is mostly tidying up, but will be useful for some PRs in the near future.
This uses the new generic parameter for the descriptor's Owner to correctly type the function's `self` parameter, among other things.
This was a one-character fix: we now need the second argument when inspecting `__orig_class__` to get the value type. This is only used when a descriptor is created using subscript syntax, e.g. `prop = Property[Thing, int](default=0)`. Happily, it was picked up in tests, and is now passing.
This now correctly uses the `Owner` type variable in `BaseDescriptor`. `mypy` picked up an inconsistency between this and `ActionDescriptor`, but oddly not on Python 3.10.
julianstirling
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Feb 2, 2026
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One thing I am confused about that could do with a comment. Otherwise this seem like a significant improvement in type specificity.
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Previously, BaseDescriptor typed the owning object as
Thing, which was a bit loose and led to some vague type hints (particularly for functional properties and actions).I've added a second generic parameter for the owning class. This makes some of the type test code a bit more verbose, but it gets rid of a fair few
type: ignorestatements and also means we now detect a few type errors that were previously missed.This is mostly tidying up, but will be useful for some PRs in the near future.
Closes #217
Closes #162