Respect runtime-required decorators on functions (#9317)

## Summary

This PR modifies the semantics of `runtime-evaluated-decorators` to
respect decorators on both classes _and_ functions. Historically, this
only respected classes, since the common use-case is (e.g.)
`pydantic.BaseModel` -- but functions are equally valid.

Closes https://github.com/astral-sh/ruff/issues/9312.

## Test Plan

`cargo test`

crates/ruff_linter/resources/test/fixtures/flake8_type_checking/runtime_evaluated_decorators_3.py

@@ -4,6 +4,8 @@ import datetime
 from array import array
 from dataclasses import dataclass
 from uuid import UUID  # TCH003
+from collections.abc import Sequence
+from pydantic import validate_call
 
 import attrs
 from attrs import frozen
@@ -22,3 +24,8 @@ class B:
 @dataclass
 class C:
     x: UUID
+
+
+@validate_call(config={'arbitrary_types_allowed': True})
+def test(user: Sequence):
+    ...

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

@@ -28,21 +28,29 @@ pub(super) enum AnnotationContext {
 impl AnnotationContext {
     pub(super) fn from_model(semantic: &SemanticModel, settings: &LinterSettings) -> Self {
         // If the annotation is in a class scope (e.g., an annotated assignment for a
-        // class field), and that class is marked as annotation as runtime-required.
+        // class field) or a function scope, and that class or function is marked as
-        if semantic
+        // runtime-required, treat the annotation as runtime-required.
-            .current_scope()
+        match semantic.current_scope().kind {
-            .kind
+            ScopeKind::Class(class_def)
-            .as_class()
+                if flake8_type_checking::helpers::runtime_required_class(
-            .is_some_and(|class_def| {
-                flake8_type_checking::helpers::runtime_required_class(
                     class_def,
                     &settings.flake8_type_checking.runtime_required_base_classes,
                     &settings.flake8_type_checking.runtime_required_decorators,
                     semantic,
-                )
+                ) =>
-            })
             {
-            return Self::RuntimeRequired;
+                return Self::RuntimeRequired
+            }
+            ScopeKind::Function(function_def)
+                if flake8_type_checking::helpers::runtime_required_function(
+                    function_def,
+                    &settings.flake8_type_checking.runtime_required_decorators,
+                    semantic,
+                ) =>
+            {
+                return Self::RuntimeRequired
+            }
+            _ => {}
         }
 
         // If `__future__` annotations are enabled, then annotations are never evaluated

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

@@ -3,7 +3,7 @@ use anyhow::Result;
 use ruff_diagnostics::Edit;
 use ruff_python_ast::call_path::from_qualified_name;
 use ruff_python_ast::helpers::map_callable;
-use ruff_python_ast::{self as ast, Expr};
+use ruff_python_ast::{self as ast, Decorator, Expr};
 use ruff_python_codegen::{Generator, Stylist};
 use ruff_python_semantic::{
     analyze, Binding, BindingKind, NodeId, ResolvedReference, SemanticModel,
@@ -43,6 +43,19 @@ pub(crate) fn is_valid_runtime_import(
     }
 }
 
+/// Returns `true` if a function's parameters should be treated as runtime-required.
+pub(crate) fn runtime_required_function(
+    function_def: &ast::StmtFunctionDef,
+    decorators: &[String],
+    semantic: &SemanticModel,
+) -> bool {
+    if runtime_required_decorators(&function_def.decorator_list, decorators, semantic) {
+        return true;
+    }
+    false
+}
+
+/// Returns `true` if a class's assignments should be treated as runtime-required.
 pub(crate) fn runtime_required_class(
     class_def: &ast::StmtClassDef,
     base_classes: &[String],
@@ -52,7 +65,7 @@ pub(crate) fn runtime_required_class(
     if runtime_required_base_class(class_def, base_classes, semantic) {
         return true;
     }
-    if runtime_required_decorators(class_def, decorators, semantic) {
+    if runtime_required_decorators(&class_def.decorator_list, decorators, semantic) {
         return true;
     }
     false
@@ -72,7 +85,7 @@ fn runtime_required_base_class(
 }
 
 fn runtime_required_decorators(
-    class_def: &ast::StmtClassDef,
+    decorator_list: &[Decorator],
     decorators: &[String],
     semantic: &SemanticModel,
 ) -> bool {
@@ -80,7 +93,7 @@ fn runtime_required_decorators(
         return false;
     }
 
-    class_def.decorator_list.iter().any(|decorator| {
+    decorator_list.iter().any(|decorator| {
         semantic
             .resolve_call_path(map_callable(&decorator.expression))
             .is_some_and(|call_path| {

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

@@ -195,6 +195,7 @@ mod tests {
                     runtime_required_decorators: vec![
                         "attrs.define".to_string(),
                         "attrs.frozen".to_string(),
+                        "pydantic.validate_call".to_string(),
                     ],
                     ..Default::default()
                 },

crates/ruff_linter/src/rules/flake8_type_checking/snapshots/ruff_linter__rules__flake8_type_checking__tests__typing-only-standard-library-import_runtime_evaluated_decorators_3.py.snap

@@ -7,8 +7,8 @@ runtime_evaluated_decorators_3.py:6:18: TCH003 [*] Move standard library import
 5 | from dataclasses import dataclass
 6 | from uuid import UUID  # TCH003
   |                  ^^^^ TCH003
-7 | 
+7 | from collections.abc import Sequence
-8 | import attrs
+8 | from pydantic import validate_call
   |
   = help: Move into type-checking block
 
@@ -17,15 +17,44 @@ runtime_evaluated_decorators_3.py:6:18: TCH003 [*] Move standard library import
 4  4  | from array import array
 5  5  | from dataclasses import dataclass
 6     |-from uuid import UUID  # TCH003
-7  6  | 
+7  6  | from collections.abc import Sequence
-8  7  | import attrs
+8  7  | from pydantic import validate_call
-9  8  | from attrs import frozen
+9  8  | 
-   9  |+from typing import TYPE_CHECKING
+10 9  | import attrs
-   10 |+
+11 10 | from attrs import frozen
-   11 |+if TYPE_CHECKING:
+   11 |+from typing import TYPE_CHECKING
-   12 |+    from uuid import UUID
+   12 |+
-10 13 | 
+   13 |+if TYPE_CHECKING:
-11 14 | 
+   14 |+    from uuid import UUID
-12 15 | @attrs.define(auto_attribs=True)
+12 15 | 
+13 16 | 
+14 17 | @attrs.define(auto_attribs=True)
+
+runtime_evaluated_decorators_3.py:7:29: TCH003 [*] Move standard library import `collections.abc.Sequence` into a type-checking block
+  |
+5 | from dataclasses import dataclass
+6 | from uuid import UUID  # TCH003
+7 | from collections.abc import Sequence
+  |                             ^^^^^^^^ TCH003
+8 | from pydantic import validate_call
+  |
+  = help: Move into type-checking block
+
+ℹ Unsafe fix
+4  4  | from array import array
+5  5  | from dataclasses import dataclass
+6  6  | from uuid import UUID  # TCH003
+7     |-from collections.abc import Sequence
+8  7  | from pydantic import validate_call
+9  8  | 
+10 9  | import attrs
+11 10 | from attrs import frozen
+   11 |+from typing import TYPE_CHECKING
+   12 |+
+   13 |+if TYPE_CHECKING:
+   14 |+    from collections.abc import Sequence
+12 15 | 
+13 16 | 
+14 17 | @attrs.define(auto_attribs=True)
 
 

crates/ruff_workspace/src/options.rs

@@ -1632,13 +1632,16 @@ pub struct Flake8TypeCheckingOptions {
     )]
     pub runtime_evaluated_base_classes: Option<Vec<String>>,
 
-    /// Exempt classes decorated with any of the enumerated decorators from
+    /// Exempt classes and functions decorated with any of the enumerated
-    /// needing to be moved into type-checking blocks.
+    /// decorators from being moved into type-checking blocks.
+    ///
+    /// Common examples include Pydantic's `@pydantic.validate_call` decorator
+    /// (for functions) and attrs' `@attrs.define` decorator (for classes).
     #[option(
         default = "[]",
         value_type = "list[str]",
         example = r#"
-            runtime-evaluated-decorators = ["attrs.define", "attrs.frozen"]
+            runtime-evaluated-decorators = ["pydantic.validate_call", "attrs.define"]
         "#
     )]
     pub runtime_evaluated_decorators: Option<Vec<String>>,

ruff.schema.json

@@ -1222,7 +1222,7 @@
           }
         },
         "runtime-evaluated-decorators": {
-          "description": "Exempt classes decorated with any of the enumerated decorators from needing to be moved into type-checking blocks.",
+          "description": "Exempt classes and functions decorated with any of the enumerated decorators from being moved into type-checking blocks.\n\nCommon examples include Pydantic's `@pydantic.validate_call` decorator (for functions) and attrs' `@attrs.define` decorator (for classes).",
           "type": [
             "array",
             "null"