[pyupgrade] Fix false positive with TypeVar default before Python 3.13 (UP040) - #26888
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… 3.13 (`UP040`) Summary -- This PR fixes a latent bug in `UP040` related to the similar changes to the other PEP-695 rules `UP046` and `UP047` in #21045. In short, `typing_extensions` backports the `default` argument for `TypeVar`s to earlier versions of Python, so checking preview alone isn't sufficient. Even the existing preview check only applied to the `TypeAlias` part of `UP040`, not the `TypeAliasType` part, so I moved the check into `create_diagnostic`, which is shared by both paths. This was never reported, so I'm planning to stabilize the preview feature in 0.16 anyway. Test Plan -- New mdtests and updates to existing snapshots
ntBre
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Preview is disabled here. This demonstrates the partial preview-gate I mentioned in the summary.
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MichaReiser
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| ) { | ||
| // If any type variables have defaults, skip the rule unless | ||
| // running with preview mode enabled and targeting Python 3.13+. | ||
| if type_vars.iter().any(|type_var| type_var.default.is_some()) |
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Nit: Maybe move the cheaper target_version and whether the rule is enabled first checks before the type vars iter check
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Summary
This PR fixes a latent bug in
UP040related to the similar changes to the other PEP-695 rulesUP046andUP047in #21045. In short,typing_extensionsbackports thedefaultargument forTypeVars to earlier versions of Python, so checking preview alone isn't sufficient. Even theexisting preview check only applied to the
TypeAliaspart ofUP040, not theTypeAliasTypepart, so I moved the check into
create_diagnostic, which is shared by both paths.This was never reported, so I'm planning to stabilize the preview feature in 0.16 anyway.
Test Plan
New mdtests and updates to existing snapshots