[pyupgrade] Fix false positive for TypeVar with default on Python <3.13 (UP046,UP047)

[prakhar1144]

Summary

Type default for Type parameter was added in Python 3.13 (PEP 696).

typing_extensions.TypeVar backports the default argument to earlier versions.

UP046 & UP047 were getting triggered when typing_extensions.TypeVar with default argument was used on python version < 3.13

It shouldn't be triggered for python version < 3.13

This commit fixes the bug by adding a python version check before triggering them.

Fixes #20929.

Test Plan

Manual testing 1

As the issue author pointed out in #20929 (comment), ran the following on main branch:

% cargo run -p ruff -- check ../efax/ --target-version py312 --no-cache

Output

 Compiling ruff_linter v0.14.1 (/Users/prakhar/ruff/crates/ruff_linter) Compiling ruff v0.14.1 (/Users/prakhar/ruff/crates/ruff) Compiling ruff_graph v0.1.0 (/Users/prakhar/ruff/crates/ruff_graph) Compiling ruff_workspace v0.0.0 (/Users/prakhar/ruff/crates/ruff_workspace) Compiling ruff_server v0.2.2 (/Users/prakhar/ruff/crates/ruff_server) Finished `dev` profile [unoptimized + debuginfo] target(s) in 6.72s Running `target/debug/ruff check ../efax/ --target-version py312 --no-cache` UP046 Generic class `ExpectationParametrization` uses `Generic` subclass instead of type parameters --> /Users/prakhar/efax/efax/_src/expectation_parametrization.py:17:48 | 17 | class ExpectationParametrization(Distribution, Generic[NP]): | ^^^^^^^^^^^ 18 | """The expectation parametrization of an exponential family distribution.  | help: Use type parameters  UP046 Generic class `ExpToNat` uses `Generic` subclass instead of type parameters  --> /Users/prakhar/efax/efax/_src/mixins/exp_to_nat/exp_to_nat.py:27:68  | 26 | @dataclass 27 | class ExpToNat(ExpectationParametrization[NP], SimpleDistribution, Generic[NP]):  | ^^^^^^^^^^^ 28 | """This mixin implements the conversion from expectation to natural parameters. | help: Use type parameters UP046 Generic class `HasEntropyEP` uses `Generic` subclass instead of type parameters --> /Users/prakhar/efax/efax/_src/mixins/has_entropy.py:25:20 | 23 | HasEntropy, 24 | JaxAbstractClass, 25 | Generic[NP]): | ^^^^^^^^^^^ 26 | @abstract_jit 27 | @abstractmethod | help: Use type parameters UP046 Generic class `HasEntropyNP` uses `Generic` subclass instead of type parameters --> /Users/prakhar/efax/efax/_src/mixins/has_entropy.py:64:20 | 62 | class HasEntropyNP(NaturalParametrization[EP], 63 | HasEntropy, 64 | Generic[EP]): | ^^^^^^^^^^^ 65 | @jit 66 | @final | help: Use type parameters UP046 Generic class `NaturalParametrization` uses `Generic` subclass instead of type parameters --> /Users/prakhar/efax/efax/_src/natural_parametrization.py:43:30 | 41 | class NaturalParametrization(Distribution, 42 | JaxAbstractClass, 43 | Generic[EP, Domain]): | ^^^^^^^^^^^^^^^^^^^ 44 | """The natural parametrization of an exponential family distribution.  | help: Use type parameters  UP046 Generic class `Structure` uses `Generic` subclass instead of type parameters  --> /Users/prakhar/efax/efax/_src/structure/structure.py:31:17  | 30 | @dataclass 31 | class Structure(Generic[P]):  | ^^^^^^^^^^ 32 | """This class generalizes the notion of type for Distribution objects. | help: Use type parameters UP046 Generic class `DistributionInfo` uses `Generic` subclass instead of type parameters --> /Users/prakhar/efax/tests/distribution_info.py:20:24 | 20 | class DistributionInfo(Generic[NP, EP, Domain]): | ^^^^^^^^^^^^^^^^^^^^^^^ 21 | def __init__(self, dimensions: int = 1, safety: float = 0.0) -> None: 22 | super().__init__() | help: Use type parameters Found 7 errors. No fixes available (7 hidden fixes can be enabled with the `--unsafe-fixes` option).

Running it after the changes:

ruff % cargo run -p ruff -- check ../efax/ --target-version py312 --no-cache Compiling ruff_linter v0.14.1 (/Users/prakhar/ruff/crates/ruff_linter) Compiling ruff v0.14.1 (/Users/prakhar/ruff/crates/ruff) Compiling ruff_graph v0.1.0 (/Users/prakhar/ruff/crates/ruff_graph) Compiling ruff_workspace v0.0.0 (/Users/prakhar/ruff/crates/ruff_workspace) Compiling ruff_server v0.2.2 (/Users/prakhar/ruff/crates/ruff_server) Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.86s Running `target/debug/ruff check ../efax/ --target-version py312 --no-cache` All checks passed!

---

Manual testing 2

Ran the check on the following script (mainly to verify UP047):

from __future__ import annotations from typing import Generic from typing_extensions import TypeVar T = TypeVar("T", default=int) def generic_function(var: T) -> T: return var Q = TypeVar("Q", default=str) class GenericClass(Generic[Q]): var: Q

On main branch:

ruff % cargo run -p ruff -- check ~/up046.py --target-version py312 --preview --no-cache

Output

 Compiling ruff_linter v0.14.1 (/Users/prakhar/ruff/crates/ruff_linter) Compiling ruff v0.14.1 (/Users/prakhar/ruff/crates/ruff) Compiling ruff_graph v0.1.0 (/Users/prakhar/ruff/crates/ruff_graph) Compiling ruff_workspace v0.0.0 (/Users/prakhar/ruff/crates/ruff_workspace) Compiling ruff_server v0.2.2 (/Users/prakhar/ruff/crates/ruff_server) Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.43s Running `target/debug/ruff check /Users/prakhar/up046.py --target-version py312 --preview --no-cache` UP047 Generic function `generic_function` should use type parameters --> /Users/prakhar/up046.py:10:5 | 10 | def generic_function(var: T) -> T: | ^^^^^^^^^^^^^^^^^^^^^^^^ 11 | return var | help: Use type parameters UP046 Generic class `GenericClass` uses `Generic` subclass instead of type parameters --> /Users/prakhar/up046.py:17:20 | 17 | class GenericClass(Generic[Q]): | ^^^^^^^^^^ 18 | var: Q | help: Use type parameters Found 2 errors. No fixes available (2 hidden fixes can be enabled with the `--unsafe-fixes` option).

After the fix (this branch):

ruff % cargo run -p ruff -- check ~/up046.py --target-version py312 --preview --no-cache Compiling ruff_linter v0.14.1 (/Users/prakhar/ruff/crates/ruff_linter) Compiling ruff v0.14.1 (/Users/prakhar/ruff/crates/ruff) Compiling ruff_graph v0.1.0 (/Users/prakhar/ruff/crates/ruff_graph) Compiling ruff_workspace v0.0.0 (/Users/prakhar/ruff/crates/ruff_workspace) Compiling ruff_server v0.2.2 (/Users/prakhar/ruff/crates/ruff_server) Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.40s Running `target/debug/ruff check /Users/prakhar/up046.py --target-version py312 --preview --no-cache` All checks passed!

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[ntBre]

Thank you! The code change and new comments look great, but would you mind converting your manual tests into regression tests in the repo?

If you already have separate Python files, they would fit nicely as new test cases alongside files like UP046_1.py and test_case entries here:

ruff/crates/ruff_linter/src/rules/pyupgrade/mod.rs

Lines 114 to 126 in 83a3bc4

	#[test_case(Rule::NonPEP695GenericFunction, Path::new("UP047.py"))]
	#[test_case(Rule::PrivateTypeParameter, Path::new("UP049_0.py"))]
	#[test_case(Rule::PrivateTypeParameter, Path::new("UP049_1.py"))]
	#[test_case(Rule::UselessClassMetaclassType, Path::new("UP050.py"))]
	fn rules(rule_code: Rule, path: &Path) -> Result<()> {
	let snapshot = path.to_string_lossy().to_string();
	let diagnostics = test_path(
	Path::new("pyupgrade").join(path).as_path(),
	&settings::LinterSettings::for_rule(rule_code),
	)?;
	assert_diagnostics!(snapshot, diagnostics);
	Ok(())
	}

Although you may need a separate test function so that you can set the version like we do here:

ruff/crates/ruff_linter/src/rules/pyupgrade/mod.rs

Line 244 in 83a3bc4

unresolved_target_version: PythonVersion::PY37.into(),

[prakhar1144]

Thanks for the review!

As an update - I got busy with festivals around; I plan to complete this in the next 2-3 days.

[prakhar1144]

@ntBre I've added tests. Ready to review.

[ntBre]

This is great, thank you!