gh-130827: Support typing.Self annotations in singledispatchmethod()
#130829
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Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
| # But, it shouldn't work on singledispatch() | ||
| with self.assertRaises(TypeError): | ||
| @test.register | ||
| def silly(self: typing.Self, arg: int | str) -> int | str: |
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Will 'typing.Self' annotation work the same way?
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Good question! It should, yeah. get_type_hints handles forward references.
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Should we add a test case for that, maybe?
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Possibly, but as long as get_type_hints is working it's probably fine.
Co-authored-by: Tomas R. <tomas.roun8@gmail.com>
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@vstinner I'd like to get this fixed before 3.12 goes security-only next week. Would you mind reviewing? |
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Wait why would we want to change this in 3.12 at all? Seems like a new feature to me. |
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I agree, this is a new feature and should not be backported. |
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Agreed with Jelle, this is a feature best left for a new release. Otherwise it's too hard to guard against in user code. |
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Makes sense. I've updated the issue. |
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Bump. I'd like to land this one before the beta freeze. |
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I think special-casing the Self annotation is the wrong approach. The self argument may be annotated with Self, but it may also be annotated with e.g. a TypeVar or Annotated.
We should be ignoring annotations not on the basis of what the annotation is, but on the basis of what parameter they're on. I think the correct approach would be to figure out the name of the first non-self argument (i.e., the second argument for a method), then retrieve the annotation for that argument.
If I'm not mistaken, singledispatch also incorrectly (or at least unintuitively) handles cases where the annotation is on some later argument, but the first one is unannotated.
@register
def f(x, random_arg: str = ...):
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Wouldn't that break if it's named something other than |
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I mean the first argument that's not conceptually |
singledispatchmethod.registerfails withtyping.Selfannotation #130827