[`flake8-pyi`] Respect local enum subclasses in `simple-defaults` (`PYI052`) (#8767)

We should reuse this approach in other rules, but this is a good start.

Closes https://github.com/astral-sh/ruff/issues/8764.

crates/ruff_linter/resources/test/fixtures/flake8_pyi/PYI052.py

@@ -91,3 +91,17 @@ field27 = list[str]
 field28 = builtins.str
 field29 = str
 field30 = str | bytes | None
+
+# We shouldn't emit Y052 for `enum` subclasses.
+from enum import Enum
+
+class Foo(Enum):
+    FOO = 0
+    BAR = 1
+
+class Bar(Foo):
+    BAZ = 2
+    BOP = 3
+
+class Bop:
+    WIZ = 4

crates/ruff_linter/resources/test/fixtures/flake8_pyi/PYI052.pyi

@@ -98,3 +98,17 @@ field27 = list[str]
 field28 = builtins.str
 field29 = str
 field30 = str | bytes | None
+
+# We shouldn't emit Y052 for `enum` subclasses.
+from enum import Enum
+
+class Foo(Enum):
+    FOO = 0
+    BAR = 1
+
+class Bar(Foo):
+    BAZ = 2
+    BOP = 3
+
+class Bop:
+    WIZ = 4

crates/ruff_linter/src/rules/flake8_pyi/rules/simple_defaults.rs

@@ -1,16 +1,17 @@
+use rustc_hash::FxHashSet;
+
 use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::call_path::CallPath;
 use ruff_python_ast::{
     self as ast, Arguments, Expr, Operator, ParameterWithDefault, Parameters, Stmt, UnaryOp,
 };
-use ruff_python_semantic::{ScopeKind, SemanticModel};
+use ruff_python_semantic::{BindingId, ScopeKind, SemanticModel};
 use ruff_source_file::Locator;
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
 use crate::importer::ImportRequest;
-
 use crate::rules::flake8_pyi::rules::TypingModule;
 use crate::settings::types::PythonVersion;
 
@@ -469,21 +470,51 @@ fn is_final_assignment(annotation: &Expr, value: &Expr, semantic: &SemanticModel
 }
 
 /// Returns `true` if the a class is an enum, based on its base classes.
-fn is_enum(arguments: Option<&Arguments>, semantic: &SemanticModel) -> bool {
-    let Some(Arguments { args: bases, .. }) = arguments else {
-        return false;
-    };
-    return bases.iter().any(|expr| {
-        semantic.resolve_call_path(expr).is_some_and(|call_path| {
-            matches!(
-                call_path.as_slice(),
-                [
-                    "enum",
-                    "Enum" | "Flag" | "IntEnum" | "IntFlag" | "StrEnum" | "ReprEnum"
-                ]
-            )
+fn is_enum(class_def: &ast::StmtClassDef, semantic: &SemanticModel) -> bool {
+    fn inner(
+        class_def: &ast::StmtClassDef,
+        semantic: &SemanticModel,
+        seen: &mut FxHashSet<BindingId>,
+    ) -> bool {
+        let Some(Arguments { args: bases, .. }) = class_def.arguments.as_deref() else {
+            return false;
+        };
+
+        bases.iter().any(|expr| {
+            // If the base class is `enum.Enum`, `enum.Flag`, etc., then this is an enum.
+            if semantic.resolve_call_path(expr).is_some_and(|call_path| {
+                matches!(
+                    call_path.as_slice(),
+                    [
+                        "enum",
+                        "Enum" | "Flag" | "IntEnum" | "IntFlag" | "StrEnum" | "ReprEnum"
+                    ]
+                )
+            }) {
+                return true;
+            }
+
+            // If the base class extends `enum.Enum`, `enum.Flag`, etc., then this is an enum.
+            if let Some(id) = semantic.lookup_attribute(expr) {
+                if seen.insert(id) {
+                    let binding = semantic.binding(id);
+                    if let Some(base_class) = binding
+                        .kind
+                        .as_class_definition()
+                        .map(|id| &semantic.scopes[*id])
+                        .and_then(|scope| scope.kind.as_class())
+                    {
+                        if inner(base_class, semantic, seen) {
+                            return true;
+                        }
+                    }
+                }
+            }
+            false
         })
-    });
+    }
+
+    inner(class_def, semantic, &mut FxHashSet::default())
 }
 
 /// Returns `true` if an [`Expr`] is a value that should be annotated with `typing.TypeAlias`.
@@ -655,10 +686,8 @@ pub(crate) fn unannotated_assignment_in_stub(
         return;
     }
 
-    if let ScopeKind::Class(ast::StmtClassDef { arguments, .. }) =
-        checker.semantic().current_scope().kind
-    {
-        if is_enum(arguments.as_deref(), checker.semantic()) {
+    if let ScopeKind::Class(class_def) = checker.semantic().current_scope().kind {
+        if is_enum(class_def, checker.semantic()) {
             return;
         }
     }

crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI052_PYI052.pyi.snap

@@ -131,4 +131,11 @@ PYI052.pyi:39:12: PYI052 Need type annotation for `field212`
 41 | field22: Final = {"foo": 5}
    |
 
+PYI052.pyi:114:11: PYI052 Need type annotation for `WIZ`
+    |
+113 | class Bop:
+114 |     WIZ = 4
+    |           ^ PYI052
+    |
+