[flake8-type-checking] Fix TC003 false positive with future-annotations (#21125)

Summary
--

Fixes #21121 by upgrading `RuntimeEvaluated` annotations like
`dataclasses.KW_ONLY` to `RuntimeRequired`. We already had special
handling for
`TypingOnly` annotations in this context but not `RuntimeEvaluated`.
Combining
that with the `future-annotations` setting, which allowed ignoring the
`RuntimeEvaluated` flag, led to the reported bug where we would try to
move
`KW_ONLY` into a `TYPE_CHECKING` block.

Test Plan
--

A new test based on the issue

crates/ruff_linter/resources/test/fixtures/flake8_type_checking/TC003.py

@@ -14,3 +14,14 @@ def f():
     import os
 
     print(os)
+
+
+# regression test for https://github.com/astral-sh/ruff/issues/21121
+from dataclasses import KW_ONLY, dataclass
+
+
+@dataclass
+class DataClass:
+    a: int
+    _: KW_ONLY  # should be an exception to TC003, even with future-annotations
+    b: int

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP037_3.py

@@ -0,0 +1,17 @@
+"""
+Regression test for an ecosystem hit on
+https://github.com/astral-sh/ruff/pull/21125.
+
+We should mark all of the components of special dataclass annotations as
+runtime-required, not just the first layer.
+"""
+
+from dataclasses import dataclass
+from typing import ClassVar, Optional
+
+
+@dataclass(frozen=True)
+class EmptyCell:
+    _singleton: ClassVar[Optional["EmptyCell"]] = None
+    # the behavior of _singleton above should match a non-ClassVar
+    _doubleton: "EmptyCell"

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -1400,6 +1400,14 @@ impl<'a> Visitor<'a> for Checker<'a> {
                     AnnotationContext::RuntimeRequired => {
                         self.visit_runtime_required_annotation(annotation);
                     }
+                    AnnotationContext::RuntimeEvaluated
+                        if flake8_type_checking::helpers::is_dataclass_meta_annotation(
+                            annotation,
+                            self.semantic(),
+                        ) =>
+                    {
+                        self.visit_runtime_required_annotation(annotation);
+                    }
                     AnnotationContext::RuntimeEvaluated => {
                         self.visit_runtime_evaluated_annotation(annotation);
                     }

crates/ruff_linter/src/rules/flake8_type_checking/mod.rs

@@ -98,6 +98,26 @@ mod tests {
         Ok(())
     }
 
+    #[test_case(Rule::TypingOnlyStandardLibraryImport, Path::new("TC003.py"))]
+    fn add_future_import_dataclass_kw_only_py313(rule: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!(
+            "add_future_import_kw_only__{}_{}",
+            rule.noqa_code(),
+            path.to_string_lossy()
+        );
+        let diagnostics = test_path(
+            Path::new("flake8_type_checking").join(path).as_path(),
+            &settings::LinterSettings {
+                future_annotations: true,
+                // The issue in #21121 also didn't trigger on Python 3.14
+                unresolved_target_version: PythonVersion::PY313.into(),
+                ..settings::LinterSettings::for_rule(rule)
+            },
+        )?;
+        assert_diagnostics!(snapshot, diagnostics);
+        Ok(())
+    }
+
     // we test these rules as a pair, since they're opposites of one another
     // so we want to make sure their fixes are not going around in circles.
     #[test_case(Rule::UnquotedTypeAlias, Path::new("TC007.py"))]

crates/ruff_linter/src/rules/flake8_type_checking/snapshots/ruff_linter__rules__flake8_type_checking__tests__add_future_import_kw_only__TC003_TC003.py.snap

@@ -0,0 +1,28 @@
+---
+source: crates/ruff_linter/src/rules/flake8_type_checking/mod.rs
+---
+TC003 [*] Move standard library import `os` into a type-checking block
+  --> TC003.py:8:12
+   |
+ 7 | def f():
+ 8 |     import os
+   |            ^^
+ 9 |
+10 |     x: os
+   |
+help: Move into type-checking block
+2  | 
+3  | For typing-only import detection tests, see `TC002.py`.
+4  | """
+5  + from typing import TYPE_CHECKING
+6  + 
+7  + if TYPE_CHECKING:
+8  +     import os
+9  | 
+10 | 
+11 | def f():
+   -     import os
+12 | 
+13 |     x: os
+14 | 
+note: This is an unsafe fix and may change runtime behavior

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

@@ -64,6 +64,7 @@ mod tests {
     #[test_case(Rule::QuotedAnnotation, Path::new("UP037_0.py"))]
     #[test_case(Rule::QuotedAnnotation, Path::new("UP037_1.py"))]
     #[test_case(Rule::QuotedAnnotation, Path::new("UP037_2.pyi"))]
+    #[test_case(Rule::QuotedAnnotation, Path::new("UP037_3.py"))]
     #[test_case(Rule::RedundantOpenModes, Path::new("UP015.py"))]
     #[test_case(Rule::RedundantOpenModes, Path::new("UP015_1.py"))]
     #[test_case(Rule::ReplaceStdoutStderr, Path::new("UP022.py"))]
@@ -156,6 +157,20 @@ mod tests {
         Ok(())
     }
 
+    #[test_case(Rule::QuotedAnnotation, Path::new("UP037_3.py"))]
+    fn rules_py313(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!("rules_py313__{}", path.to_string_lossy());
+        let diagnostics = test_path(
+            Path::new("pyupgrade").join(path).as_path(),
+            &settings::LinterSettings {
+                unresolved_target_version: PythonVersion::PY313.into(),
+                ..settings::LinterSettings::for_rule(rule_code)
+            },
+        )?;
+        assert_diagnostics!(snapshot, diagnostics);
+        Ok(())
+    }
+
     #[test_case(Rule::NonPEP695TypeAlias, Path::new("UP040.py"))]
     #[test_case(Rule::NonPEP695TypeAlias, Path::new("UP040.pyi"))]
     #[test_case(Rule::NonPEP695GenericClass, Path::new("UP046_0.py"))]

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP037_3.py.snap

@@ -0,0 +1,36 @@
+---
+source: crates/ruff_linter/src/rules/pyupgrade/mod.rs
+---
+UP037 [*] Remove quotes from type annotation
+  --> UP037_3.py:15:35
+   |
+13 | @dataclass(frozen=True)
+14 | class EmptyCell:
+15 |     _singleton: ClassVar[Optional["EmptyCell"]] = None
+   |                                   ^^^^^^^^^^^
+16 |     # the behavior of _singleton above should match a non-ClassVar
+17 |     _doubleton: "EmptyCell"
+   |
+help: Remove quotes
+12 | 
+13 | @dataclass(frozen=True)
+14 | class EmptyCell:
+   -     _singleton: ClassVar[Optional["EmptyCell"]] = None
+15 +     _singleton: ClassVar[Optional[EmptyCell]] = None
+16 |     # the behavior of _singleton above should match a non-ClassVar
+17 |     _doubleton: "EmptyCell"
+
+UP037 [*] Remove quotes from type annotation
+  --> UP037_3.py:17:17
+   |
+15 |     _singleton: ClassVar[Optional["EmptyCell"]] = None
+16 |     # the behavior of _singleton above should match a non-ClassVar
+17 |     _doubleton: "EmptyCell"
+   |                 ^^^^^^^^^^^
+   |
+help: Remove quotes
+14 | class EmptyCell:
+15 |     _singleton: ClassVar[Optional["EmptyCell"]] = None
+16 |     # the behavior of _singleton above should match a non-ClassVar
+   -     _doubleton: "EmptyCell"
+17 +     _doubleton: EmptyCell

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__rules_py313__UP037_3.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff_linter/src/rules/pyupgrade/mod.rs
+---
+