[ty] Synthesize `__init__` for `TypedDict` by Glyphack · Pull Request #24476 · astral-sh/ruff

Glyphack · 2026-04-07T21:16:48Z

Summary

This PR adds a synthesized __init__ method for TypedDict that is used in server for hover.

The new method is not used for type checking.
The reason is that the current sophisticated validation logic has better UX than normal argument matching.

The __init__ method has two bindings right now:

class Movie(TypedDict):
    title: str
    year: int

class Movie(
    __map: Movie,
    /,
    *,
    title: str = ...,
    year: int = ...
)

class Movie(
    *,
    title: str = ...,
    year: int = ...
)

I removed the previous TODO to use synthesized method for type checking since this is being implemented with another solution. #24450.

Test Plan

astral-sh-bot · 2026-04-07T21:19:13Z

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 87.72%. The percentage of expected errors that received a diagnostic held steady at 82.85%. The number of fully passing files held steady at 74/132.

astral-sh-bot · 2026-04-07T21:20:08Z

Memory usage report

Memory usage unchanged ✅

astral-sh-bot · 2026-04-07T21:21:58Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`invalid-await`	40	0	0
`invalid-return-type`	1	0	0
Total	41	0	0

Changes in flaky projects detected. Raw diff output excludes flaky projects; see the HTML report for details.

Full report with detailed diff (timing results)

MichaReiser · 2026-04-09T13:01:56Z

I haven't yet looked at the code but this surprisingly doesn't fix astral-sh/ty#3207 (PR #24378). Probably because the parameter lookup tries to lookup the function definition which doesn't exist for synthesized constructors. So we might need something that works for synthesized constructors too (obviously, not something that needs doing in this PR)

charliermarsh · 2026-04-09T17:52:12Z

+        Parameter::positional_only(Some(Name::new_static("self"))).with_annotated_type(instance_ty);
+
+    let map_param = Parameter::positional_only(Some(Name::new_static("__map")))
+        .with_annotated_type(instance_ty);


Technically... this can be a subset of the instance type, if any missing fields are provided by the following keyword arguments. I'm not sure if we want to try modeling that -- does it even matter for the IDE cases?

is it possible to model that? (maybe by iterating the fields and using type dict[str, str | int]?) pyright and pyrefly are showing the class type.
I think it's useful to let the user know about this what kind of keys it accepts but that can also be something we can add as docstring to this signature to explain it if users need more guidance with the signature.

I doubt it. I think we should just ignore it.

But maybe acknowledge it in function header?

I'll add and merge.

* main: [ty] Fix bad diagnostic range for incorrect implicit `__init_subclass__` calls (#24541) [ty] Add a `SupportedPythonVersion` enum (#24412) [ty] Ignore unsupported editor-selected Python versions (#24498) [ty] Add snapshots for `__init_subclass__` diagnostics (#24539) [ty] Minor fix in tests (#24538) [ty] Allow `Final` variable assignments in `__post_init__` (#24529) [ty] Expand test suite for assignment errors (#24537) [ty] Use `map`, not `__map`, as the name of the mapping parameter in `TypedDict` `__init__` methods (#24535) [ty] Rework logic for synthesizing `TypedDict` methods (#24534) [flake8-bandit] Fix S103 false positives and negatives in mask analysis (#24424) [ty] mdtest.py: update dependencies (#24533) Rename patterns and arguments source order iterator method (#24532) [ty] Omit invalid keyword arguments from `TypedDict` signature (#24522) [ty] support super() in metaclass methods (#24483) [ty] Synthesize `__init__` for `TypedDict` (#24476)

* main: Bump typing conformance suite commit to latest upstream (#24553) [ty] Reject deleting`Final` attributes (#24508) [ty] Respect property deleters in attribute deletion checks (#24500) [ty] stop unioning Unknown into types of un-annotated attributes (#24531) [ty] Fix bad diagnostic range for incorrect implicit `__init_subclass__` calls (#24541) [ty] Add a `SupportedPythonVersion` enum (#24412) [ty] Ignore unsupported editor-selected Python versions (#24498) [ty] Add snapshots for `__init_subclass__` diagnostics (#24539) [ty] Minor fix in tests (#24538) [ty] Allow `Final` variable assignments in `__post_init__` (#24529) [ty] Expand test suite for assignment errors (#24537) [ty] Use `map`, not `__map`, as the name of the mapping parameter in `TypedDict` `__init__` methods (#24535) [ty] Rework logic for synthesizing `TypedDict` methods (#24534) [flake8-bandit] Fix S103 false positives and negatives in mask analysis (#24424) [ty] mdtest.py: update dependencies (#24533) Rename patterns and arguments source order iterator method (#24532) [ty] Omit invalid keyword arguments from `TypedDict` signature (#24522) [ty] support super() in metaclass methods (#24483) [ty] Synthesize `__init__` for `TypedDict` (#24476)

## Summary  This PR adds a synthesized `__init__` method for `TypedDict` that is used in server for hover. The new method is not used for type checking. The reason is that the current sophisticated validation logic has better UX than normal argument matching. The `__init__` method has two bindings right now: ``` class Movie(TypedDict): title: str year: int class Movie( __map: Movie, /, *, title: str = ..., year: int = ... ) class Movie( *, title: str = ..., year: int = ... ) ``` I removed the previous TODO to use synthesized method for type checking since this is being implemented with another solution. #24450. ## Test Plan  --------- Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

astral-sh-bot Bot added the ty Multi-file analysis & type inference label Apr 7, 2026

Glyphack changed the title ~~Synthesize __init__ for TypedDict~~ [ty] Synthesize __init__ for TypedDict Apr 7, 2026

Glyphack force-pushed the shaygan-typedict-binding branch from 25d963d to 3cdb5ce Compare April 9, 2026 05:43

Glyphack marked this pull request as ready for review April 9, 2026 05:54

Glyphack requested review from AlexWaygood, BurntSushi, Gankra, MichaReiser, carljm, dcreager, ibraheemdev and sharkdp as code owners April 9, 2026 05:54

astral-sh-bot Bot assigned charliermarsh Apr 9, 2026

astral-sh-bot Bot requested a review from charliermarsh April 9, 2026 05:54

carljm removed their request for review April 9, 2026 05:56

AlexWaygood added the server Related to the LSP server label Apr 9, 2026

charliermarsh reviewed Apr 9, 2026

View reviewed changes

charliermarsh approved these changes Apr 9, 2026

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Glyphack added 8 commits April 9, 2026 14:57

Synthesize __init__ for TypedDict

cb7b8ab

Remove todo

dd0b4d8

Add a test case with dict expression

b3a9856

Add test case for NotRequired and total=False

1517c6e

Use type context for inferring dict literal in Typed Dict

8f49fea

Update snapshots

e3b9aac

Remove todo

e31fc09

Rename

92522ad

Tweak comment

6dca88a

charliermarsh force-pushed the shaygan-typedict-binding branch from 30afc50 to 6dca88a Compare April 9, 2026 18:57

charliermarsh merged commit 239a6cb into astral-sh:main Apr 9, 2026
55 checks passed

Glyphack deleted the shaygan-typedict-binding branch April 10, 2026 04:31

AlexWaygood mentioned this pull request Apr 10, 2026

[ty] Rework logic for synthesizing TypedDict methods #24534

Merged

This was referenced Apr 27, 2026

Always include panic payload in panic diagnostic message #24873

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ASCII identifier fast path #24876

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[ty] Synthesize `init` for `TypedDict`#24476

[ty] Synthesize `init` for `TypedDict`#24476
charliermarsh merged 9 commits intoastral-sh:mainfrom
Glyphack:shaygan-typedict-binding

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