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GeezerVison is showing github.com — gh-130827: Support `typing.Self` annotations in `singledispatchmethod()` by ZeroIntensity · Pull Request #130829 · python/cpython

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@ZeroIntensity

@ZeroIntensity ZeroIntensity commented Mar 4, 2025 •
edited by bedevere-app Bot
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  • Issue: singledispatchmethod.register fails with typing.Self annotation #130827

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ZeroIntensity added 2 commits March 4, 2025 06:56
@ZeroIntensity
pythongh-130827: Support typing.Self in singledispatchmethod()
d466dc4
@ZeroIntensity
Add blurb.
fd7e374
@ZeroIntensity ZeroIntensity added topic-typing needs backport to 3.12 only security fixes needs backport to 3.13 only security fixes labels Mar 4, 2025
@ZeroIntensity
ZeroIntensity requested a review from JelleZijlstra March 4, 2025 11:59
@ZeroIntensity
ZeroIntensity requested a review from rhettinger as a code owner March 4, 2025 11:59
@bedevere-app bedevere-app Bot added the awaiting review label Mar 4, 2025
@bedevere-app bedevere-app Bot mentioned this pull request Mar 4, 2025
singledispatchmethod.register fails with typing.Self annotation #130827
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picnixz
picnixz reviewed Mar 4, 2025
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Comment thread Lib/test/test_functools.py Resolved

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@ZeroIntensity @picnixz
Update Lib/test/test_functools.py
2e6b46f 
Co-authored-by: Bénédikt Tran <[email protected]>
sobolevn
sobolevn reviewed Mar 4, 2025
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Comment thread Lib/test/test_functools.py
# But, it shouldn't work on singledispatch()
with self.assertRaises(TypeError):
@test.register
def silly(self: typing.Self, arg: int | str) -> int | str:

@sobolevn sobolevn Mar 4, 2025

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Will 'typing.Self' annotation work the same way?

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@ZeroIntensity ZeroIntensity Mar 4, 2025

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Good question! It should, yeah. get_type_hints handles forward references.

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@sobolevn sobolevn Mar 4, 2025

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Should we add a test case for that, maybe?

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@ZeroIntensity ZeroIntensity Mar 4, 2025

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Possibly, but as long as get_type_hints is working it's probably fine.

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tomasr8
tomasr8 reviewed Mar 4, 2025
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Comment thread Lib/functools.py Resolved

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@ZeroIntensity @tomasr8
Update Lib/functools.py
f571ec7 
Co-authored-by: Tomas R. <[email protected]>
JelleZijlstra
JelleZijlstra reviewed Mar 4, 2025
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Comment thread Lib/functools.py Resolved

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ZeroIntensity added 2 commits March 17, 2025 13:11
@ZeroIntensity
Add some checks for edge cases.
658d3fe
@ZeroIntensity
Fix code written with stupid nano.
2558b74
@ZeroIntensity
ZeroIntensity requested review from JelleZijlstra and sobolevn March 17, 2025 13:13
@ZeroIntensity
Fix indentation in comment.
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@ZeroIntensity

ZeroIntensity commented Apr 2, 2025

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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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@vstinner

vstinner commented Apr 2, 2025

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@vstinner I'd like to get this fixed before 3.12 goes security-only next week. Would you mind reviewing?

That's out of my domain expertise.

@ambv would be a better reviewer for this task ;-)
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@JelleZijlstra

JelleZijlstra commented Apr 2, 2025

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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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@sobolevn sobolevn removed needs backport to 3.12 only security fixes needs backport to 3.13 only security fixes labels Apr 2, 2025
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sobolevn commented Apr 2, 2025

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I agree, this is a new feature and should not be backported.
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@ambv

ambv commented Apr 2, 2025

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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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@ZeroIntensity

ZeroIntensity commented Apr 2, 2025

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Makes sense. I've updated the issue.
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@ZeroIntensity
Merge branch 'main' into typing-self-singledispatch
65a9a95
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ZeroIntensity commented Apr 29, 2025

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Bump. I'd like to land this one before the beta freeze.
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JelleZijlstra
JelleZijlstra requested changes May 4, 2025
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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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@bedevere-app bedevere-app Bot added awaiting changes and removed awaiting review labels May 4, 2025
@bedevere-app

bedevere-app Bot commented May 4, 2025

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A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.
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@ZeroIntensity

ZeroIntensity commented May 4, 2025

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I think the correct approach would be to figure out the name of the first non-self argument

Wouldn't that break if it's named something other than self?
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@JelleZijlstra

JelleZijlstra commented May 4, 2025

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I mean the first argument that's not conceptually self. We shouldn't look at the name.
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@johnslavik johnslavik mentioned this pull request Oct 17, 2025
gh-84644: Don't single-dispatch on return types #140255
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github-actions Bot commented Apr 22, 2026

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This PR is stale because it has been open for 30 days with no activity.
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@github-actions github-actions Bot added the stale Stale PR or inactive for long period of time. label Apr 22, 2026
@ZeroIntensity

ZeroIntensity commented Apr 22, 2026

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I think @johnslavik has a different solution that he's been working on -- I'm going to close this in favor of his work.
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@ZeroIntensity ZeroIntensity closed this Apr 22, 2026
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Reviewers

@tomasr8 tomasr8 tomasr8 left review comments
@picnixz picnixz picnixz left review comments
@JelleZijlstra JelleZijlstra JelleZijlstra requested changes
@rhettinger rhettinger Awaiting requested review from rhettinger rhettinger is a code owner
@sobolevn sobolevn Awaiting requested review from sobolevn

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7 participants

@ZeroIntensity @vstinner @JelleZijlstra @sobolevn @ambv @tomasr8 @picnixz
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