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Add rule for context manager iterator annotations (UP052) - #29000
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charliermarsh merged 4 commits intoSep 30, 2026
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| code | total | + violation | - violation | + fix | - fix |
|---|---|---|---|---|---|
| context-manager-generator | 341 | 341 | 0 | 0 | 0 |
| UP052 | 1 | 1 | 0 | 0 | 0 |
charliermarsh
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September 30, 2026 01:09
ntBre
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Sep 30, 2026
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| /// @contextmanager | ||
| /// def example() -> Generator[int, None, None]: | ||
| /// yield 1 |
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Do we/should we generate the shorter Generator[int] form on 3.13+? It also seems okay to leave it to unnecessary-default-type-args (UP043), though.
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| let return_type = if visitor.returns_value { | ||
| "object" | ||
| } else { | ||
| "None" | ||
| }; | ||
| let (object_edit, return_type) = if visitor.returns_value { | ||
| checker.importer().get_or_import_builtin_symbol( | ||
| return_type, | ||
| function.start(), | ||
| checker.semantic(), | ||
| )? | ||
| } else { | ||
| (None, return_type.to_string()) | ||
| }; |
Contributor
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This first return_type binding seems kind of redundant, if I understand correctly:
Suggested change
| let return_type = if visitor.returns_value { | |
| "object" | |
| } else { | |
| "None" | |
| }; | |
| let (object_edit, return_type) = if visitor.returns_value { | |
| checker.importer().get_or_import_builtin_symbol( | |
| return_type, | |
| function.start(), | |
| checker.semantic(), | |
| )? | |
| } else { | |
| (None, return_type.to_string()) | |
| }; | |
| let (object_edit, return_type) = if visitor.returns_value { | |
| checker.importer().get_or_import_builtin_symbol( | |
| "object", | |
| function.start(), | |
| checker.semantic(), | |
| )? | |
| } else { | |
| (None, "None".to_string()) | |
| }; |
| /// - [Python documentation: `contextlib.asynccontextmanager`](https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager) | ||
| #[derive(ViolationMetadata)] | ||
| #[violation_metadata(preview_since = "NEXT_RUFF_VERSION", category = Category::Suspicious)] | ||
| pub(crate) struct ContextManagerGenerator { |
Contributor
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nit: Should this be ContextManagerIterator since that's the issue being flagged in the initial code?
| } | ||
|
|
||
| #[test] | ||
| fn context_manager_generator_fixes() -> Result<()> { |
Contributor
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Could we just use a regular snapshot here? Or maybe mdtests?
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Summary
The
contextmanagerandasynccontextmanagerdecorators require generators, which support methods not guaranteed by theIteratorandAsyncIteratorprotocols. Typeshed deprecates the overloads that accept these iterator annotations.Add the preview rule
context-manager-iterator(UP052) to identify these annotations and offer a fix. For example:The fix replaces
Iterator[int]withGenerator[int, None, None]. For an async context manager, it replacesAsyncIterator[int]withAsyncGenerator[int, None]. On Python 3.13 and later, it omits the default type arguments and usesGenerator[int]orAsyncGenerator[int]. If a synchronous generator returns a value, the fix usesobjectas its return type.The fix is unsafe because it changes runtime annotations and may introduce an import. The rule checks functions whose innermost decorator is a context manager and whose body contains a
yieldoryield from.