[ty] Complete support for more detailed diagnostics on possibly unbound errors from implicit dunder calls against unions.#24676
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[ty] Complete support for more detailed diagnostics on possibly unbound errors from implicit dunder calls against unions.#24676
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 87.94%. The percentage of expected errors that received a diagnostic held steady at 83.36%. The number of fully passing files held steady at 79/133. |
Memory usage reportMemory usage unchanged ✅ |
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…m context manager dunder methods invoked on a union. (#24662) <!-- Thank you for contributing to Ruff/ty! To help us out with reviewing, please consider the following: - Does this pull request include a summary of the change? (See below.) - Does this pull request include a descriptive title? (Please prefix with `[ty]` for ty pull requests.) - Does this pull request include references to any relevant issues? - Does this PR follow our AI policy (https://github.com/astral-sh/.github/blob/main/AI_POLICY.md)? --> ## 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.
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| info: Definition of class `Foo` will raise `TypeError` at runtime | ||
| info: An instance type is only a valid class base if it has a valid `__mro_entries__` method | ||
| info: Type `HasMroEntries | NoMroEntries` may have an `__mro_entries__` attribute, but it may be missing | ||
| info: `NoMroEntries` does not implement `__mro_entries__` |
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I would appreciate feedback on whether or not we should consolidate or eliminate some info diagnostics in this case. The current pattern is clear and each sub-diagnostic is informative, but 4 separate diagnostics might be considered a bit excessive.
lerebear
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ibraheemdev and
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Summary
Building on #24662, and to resolve astral-sh/ty#940, this adds more "info" sub-diagnostics to possibly unbound method error messages that occur when a dunder is called implicitly against a union type. The implicit dunder calls covered here are
__iter__,__await__and__mro_entries__.Test Plan
Please see new/updated mdtests and related snapshots.