[ty] chore: `ContextManagerError` message update by Y3K · Pull Request #20199 · astral-sh/ruff

Y3K · 2025-09-01T19:28:22Z

Summary

Test Plan

class Bound:
    def __enter__(self): ...

    def __exit__(self, *args): ...


class EnterUnbound:
    def __exit__(self): ...


class ExitUnbound:
    def __enter__(self): ...


class Unbound: ...


def bound(x: Bound):
    with x: ...


def enter_unbound(x: EnterUnbound):
    with x: ...


def exit_unbound(x: ExitUnbound):
    with x: ...


def unbound(x: Unbound):
    with x: ...


def union_enter_unbound(x: Bound | EnterUnbound):
    with x: ...


def union_exit_unbound(x: Bound | ExitUnbound):
    with x: ...


def union_unbound(x: Bound | Unbound):
    with x: ...


def multiple(x: Bound | EnterUnbound | ExitUnbound):
    with x: ...

$ cargo run --bin ty -- check --project ../pydummy

error[invalid-context-manager]: Object of type `EnterUnbound` cannot be used with `with` because it does not implement `__enter__`, and it does not correctly implement `__exit__`
  --> ../pydummy/main.py:23:10
   |
22 | def enter_unbound(x: EnterUnbound):
23 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `ExitUnbound` cannot be used with `with` because it does not implement `__exit__`
  --> ../pydummy/main.py:27:10
   |
26 | def exit_unbound(x: ExitUnbound):
27 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `Unbound` cannot be used with `with` because it does not implement `__enter__` and `__exit__`
  --> ../pydummy/main.py:31:10
   |
30 | def unbound(x: Unbound):
31 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `Bound | EnterUnbound` cannot be used with `with` because the method `__enter__` of `EnterUnbound` is possibly unbound
  --> ../pydummy/main.py:35:10
   |
34 | def union_enter_unbound(x: Bound | EnterUnbound):
35 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `Bound | ExitUnbound` cannot be used with `with` because the method `__exit__` of `ExitUnbound` is possibly unbound
  --> ../pydummy/main.py:39:10
   |
38 | def union_exit_unbound(x: Bound | ExitUnbound):
39 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `Bound | Unbound` cannot be used with `with` because the methods `__enter__` and `__exit__` of `Unbound` are possibly unbound
  --> ../pydummy/main.py:43:10
   |
42 | def union_unbound(x: Bound | Unbound):
43 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

error[invalid-context-manager]: Object of type `Bound | EnterUnbound | ExitUnbound` cannot be used with `with` because the method `__enter__` of `EnterUnbound` is possibly unbound, and the method `__exit__` of `ExitUnbound` is possibly unbound
  --> ../pydummy/main.py:47:10
   |
46 | def multiple(x: Bound | EnterUnbound | ExitUnbound):
47 |     with x: ...
   |          ^
   |
info: rule `invalid-context-manager` is enabled by default

github-actions · 2025-09-01T19:41:14Z

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

github-actions · 2025-09-01T19:44:00Z

`mypy_primer` results

Changes were detected when running on open source projects

prefect (https://github.com/PrefectHQ/prefect)
- src/prefect/artifacts.py:675:16: error[invalid-context-manager] Object of type `nullcontext[PrefectClient & ~AlwaysFalsy] | PrefectClient` cannot be used with `async with` because the methods `__aenter__` and `__aexit__` are possibly unbound
+ src/prefect/artifacts.py:675:16: error[invalid-context-manager] Object of type `nullcontext[PrefectClient & ~AlwaysFalsy] | PrefectClient` cannot be used with `async with` because the methods `__aenter__` and `__aexit__` of `nullcontext[PrefectClient & ~AlwaysFalsy]` are possibly unbound

xarray (https://github.com/pydata/xarray)
- xarray/tests/test_distributed.py:316:14: error[invalid-context-manager] Object of type `Unknown | None` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ xarray/tests/test_distributed.py:316:14: error[invalid-context-manager] Object of type `Unknown | None` cannot be used with `with` because the methods `__enter__` and `__exit__` of `None` are possibly unbound

pandas (https://github.com/pandas-dev/pandas)
- pandas/tests/io/test_stata.py:1302:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1302:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1347:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1347:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1351:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1351:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1355:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1355:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1359:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1359:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1364:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1364:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1400:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1400:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1427:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1427:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:1692:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:1692:14: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound
- pandas/tests/io/test_stata.py:2351:10: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound
+ pandas/tests/io/test_stata.py:2351:10: error[invalid-context-manager] Object of type `DataFrame | StataReader` cannot be used with `with` because the methods `__enter__` and `__exit__` of `DataFrame` are possibly unbound

No memory usage changes detected ✅

carljm

Thanks for the pull request! This is definitely an improvement.

My idea when I filed the issue was that we would bubble up the information about which types had the dunder unbound or possibly-unbound as part of the CallDunderError, but looking at it now I see this would probably require special-casing Type::Union in try_call_dunder (because member_lookup_with_policy squashes union information into a single PlaceAndQualifiers). I still think this might make sense, but I also think it's OK to just re-create the information once we know there's a problem.

carljm · 2025-09-02T23:54:05Z

 ```

+## Union context managers with specific member issues
+


We can snapshot diagnostics for these tests, which is an easier way to see the full resulting diagnostic, instead of putting full error messages directly in the mdtest. This is usually preferred for tests focused on diagnostic rendering, and is especially useful when the diagnostic is not all crammed into a single sentence, as I suggest below.

Suggested change



Then you use cargo insta test -p ty_python_semantic to generate new snapshots to review with cargo insta review and then commit.

Sorry for the rookie question.

Can I get a really brief example of how snapshots work?

e.g. should be snapshotted in main or post changes? What if the message changes do I need to update snaps? Are all the snaps run when I do cargo nextest run?

carljm · 2025-09-02T23:55:03Z

+
+    context_expr = Bound() if flag else EnterUnbound()
+
+    # error: [invalid-context-manager] "Object of type `Bound | EnterUnbound` cannot be used with `async with` because the method `__aenter__` of `EnterUnbound` is possibly unbound"


E.g. if we snapshot diagnostics, then we can just do this here:

Suggested change

# error: [invalid-context-manager] "Object of type `Bound | EnterUnbound` cannot be used with `async with` because the method `__aenter__` of `EnterUnbound` is possibly unbound"

# error: [invalid-context-manager]

Y3K · 2025-09-03T14:44:15Z

Thank you for your review @carljm!

I'm quite rookie with Rust and ty therefore the changes requested still are a bit confussing to me.

I'll read each suggestion carefully and work on a new approach, will ping you once it's ready.

Thanks!

carljm · 2025-09-03T14:56:50Z

@Y3K happy to offer clarification on any comments. I think for purposes of this PR you can ignore the comment about "bubbling up the information through CallDunderError", and you can ignore one other comment I'll mention inline. The other ones I think don't require an entirely "new approach" to address, just some updates to the current approach.

Y3K · 2025-09-03T15:04:14Z

Thank you again, @carljm !

I don't want to waste a lot of your time, but I do accept any extra help you want and can provide.

Will address all your feedback within this PR 🙌🏼

sharkdp · 2026-02-03T12:44:08Z

I'm closing this due to inactivity. Please feel free to comment in case it should be re-opened.

I'll add a comment to the linked ticket that this is useful as a resource if someone picks that task up again.

…m context manager dunder methods invoked on a union. (#24662)  ## Summary As part of astral-sh/ty#940, this helps us emit more specific diagnostics for possibly unbound context manager dunders (e.g., `__enter__`, `__exit__`) invoked on a union type. Where previously the following snippet would produce just the top-level diagnostic commented below: ```py class Context: def __enter__(self): ... def __exit__(self, *args): ... class NotContext: pass def _(x: Context | NotContext): # error: [invalid-context-manager] "Object of type `Context | NotContext` cannot be used with `with` because the methods `__enter__` and `__exit__` are possibly unbound" with x: pass ``` We will now produce two further "info" sub-diagnostics: ``` info: `NotContext` does not implement `__enter__` info: `NotContext` does not implement `__exit__` ``` ## Approach - This implements the approach suggested by `@carljm` [here](#20199 (review)) from a previous attempt to address astral-sh/ty#940; it extends `CallDunderError::PossiblyUnbound` with a new `unbound_on` field that stores a list of the union members on which a particular dunder is unbound. We create the new, richer error with a new `UnionType.try_call_dunder_with_policy` method that looks up the dunder on each member of the union, and then aggregates the results. This is supersedes the previous `UnionType.map_with_boundness_and_qualifiers` approach, and allows us to preserve the per-member binding information that we use to produce the more detailed diagnostic. - There are two alternatives to this approach that I considered but rejected: - Rebuild the specific union member diagnositic information at each callsite, and only when relevant. This was the approach originally taken by #20199, but I think it will lead to some unnecessary code duplication across callsites (of which there are at least three more). - Refactor such that `UnionType.map_with_boundness_and_qualifiers` such that it no longer loses member-specific binding information when producing its result. This would have required an extension to `PlaceAndQualifiers`, which would have a large blast radius and also introduce overhead in several cases where member-specific information for unions is not necessary. - There are more implicit dunder calls that can benefit from the new shape of `CallDunderError::PossiblyUnbound`, but I have intentionally deferred those to [a follow-up](#24676) in order to first collect feedback on a more targeted changeset. - The first three commits in this PR (926bcec, 65dc3fb, 988e81d) are "prefactors" that do not change any observable behaviour. The fourth (2422844) actually implements the improvement, and deserves the most scrutiny. ## Test Plan Please see updated mdtests and associated snapshots.

Y3K requested review from AlexWaygood, carljm, dcreager and sharkdp as code owners September 1, 2025 19:28

Y3K force-pushed the chore/ContextManageError_message_update branch from 06686e9 to 0fdf81e Compare September 1, 2025 19:54

Y3K changed the title ~~[ty] chore: ContextManagerError message update~~ [ty] chore: ContextManagerError message update Sep 1, 2025

chore: ContextManagerError message update

9733d41

Y3K force-pushed the chore/ContextManageError_message_update branch from 0fdf81e to 9733d41 Compare September 1, 2025 21:49

ntBre added the ty Multi-file analysis & type inference label Sep 2, 2025

carljm requested changes Sep 3, 2025

View reviewed changes

sharkdp removed their request for review September 3, 2025 07:22

chore: Remove unused returned vec

f619cbd

Y3K marked this pull request as draft September 3, 2025 17:33

draft: Address feedback

67846c0

Y3K force-pushed the chore/ContextManageError_message_update branch from aee5519 to 67846c0 Compare September 3, 2025 17:34

sharkdp closed this Feb 3, 2026

sharkdp mentioned this pull request Feb 3, 2026

improve diagnostics for possibly-unbound call-dunder with union astral-sh/ty#940

Closed

lerebear mentioned this pull request Apr 15, 2026

[ty] Emit more specific diagnostics for "possibly unbound" errors from context manager dunder methods invoked on a union. #24662

Merged


		context_expr = Bound() if flag else EnterUnbound()

		# error: [invalid-context-manager] "Object of type `Bound \| EnterUnbound` cannot be used with `async with` because the method `__aenter__` of `EnterUnbound` is possibly unbound"

	# error: [invalid-context-manager] "Object of type `Bound \| EnterUnbound` cannot be used with `async with` because the method `__aenter__` of `EnterUnbound` is possibly unbound"
	# error: [invalid-context-manager]

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Y3K commented Sep 1, 2025

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