[PIE796] don't report when using ellipses for enum values in stub files (#8825)

## Summary

Just ignores ellipses as enum values inside stub files.

Fixes #8818.

crates/ruff_linter/resources/test/fixtures/flake8_pie/PIE796.py

@@ -64,3 +64,9 @@ class FakeEnum10(enum.Enum):
     A = enum.auto()
     B = enum.auto()
     C = enum.auto()
+
+
+class FakeEnum10(enum.Enum):
+    A = ...
+    B = ...  # PIE796
+    C = ...  # PIE796

crates/ruff_linter/resources/test/fixtures/flake8_pie/PIE796.pyi

@@ -0,0 +1,7 @@
+import enum
+
+
+class FakeEnum1(enum.Enum):
+    A = ...
+    B = ...
+    C = ...

crates/ruff_linter/src/rules/flake8_pie/mod.rs

@@ -21,6 +21,7 @@ mod tests {
     #[test_case(Rule::UnnecessarySpread, Path::new("PIE800.py"))]
     #[test_case(Rule::ReimplementedContainerBuiltin, Path::new("PIE807.py"))]
     #[test_case(Rule::NonUniqueEnums, Path::new("PIE796.py"))]
+    #[test_case(Rule::NonUniqueEnums, Path::new("PIE796.pyi"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
         let diagnostics = test_path(

crates/ruff_linter/src/rules/flake8_pie/rules/non_unique_enums.rs

@@ -4,7 +4,7 @@ use ruff_diagnostics::Diagnostic;
 use ruff_diagnostics::Violation;
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::comparable::ComparableExpr;
-use ruff_python_ast::{self as ast, Expr, Stmt};
+use ruff_python_ast::{self as ast, Expr, PySourceType, Stmt};
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
@@ -84,7 +84,15 @@ pub(crate) fn non_unique_enums(checker: &mut Checker, parent: &Stmt, body: &[Stm
             }
         }
 
-        if !seen_targets.insert(ComparableExpr::from(value)) {
+        let comparable = ComparableExpr::from(value);
+
+        if checker.source_type == PySourceType::Stub
+            && comparable == ComparableExpr::EllipsisLiteral
+        {
+            continue;
+        }
+
+        if !seen_targets.insert(comparable) {
             let diagnostic = Diagnostic::new(
                 NonUniqueEnums {
                     value: checker.generator().expr(value),

crates/ruff_linter/src/rules/flake8_pie/snapshots/ruff_linter__rules__flake8_pie__tests__PIE796_PIE796.py.snap

@@ -57,4 +57,21 @@ PIE796.py:54:5: PIE796 Enum contains duplicate value: `2`
    |     ^^^^^ PIE796
    |
 
+PIE796.py:71:5: PIE796 Enum contains duplicate value: `...`
+   |
+69 | class FakeEnum10(enum.Enum):
+70 |     A = ...
+71 |     B = ...  # PIE796
+   |     ^^^^^^^ PIE796
+72 |     C = ...  # PIE796
+   |
+
+PIE796.py:72:5: PIE796 Enum contains duplicate value: `...`
+   |
+70 |     A = ...
+71 |     B = ...  # PIE796
+72 |     C = ...  # PIE796
+   |     ^^^^^^^ PIE796
+   |
+
 

crates/ruff_linter/src/rules/flake8_pie/snapshots/ruff_linter__rules__flake8_pie__tests__PIE796_PIE796.pyi.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff_linter/src/rules/flake8_pie/mod.rs
+---
+

crates/ruff_python_ast/src/comparable.rs

@@ -766,7 +766,7 @@ pub enum ComparableExpr<'a> {
     NumberLiteral(ExprNumberLiteral<'a>),
     BoolLiteral(ExprBoolLiteral<'a>),
     NoneLiteral,
-    EllispsisLiteral,
+    EllipsisLiteral,
     Attribute(ExprAttribute<'a>),
     Subscript(ExprSubscript<'a>),
     Starred(ExprStarred<'a>),
@@ -964,7 +964,7 @@ impl<'a> From<&'a ast::Expr> for ComparableExpr<'a> {
                 Self::BoolLiteral(ExprBoolLiteral { value })
             }
             ast::Expr::NoneLiteral(_) => Self::NoneLiteral,
-            ast::Expr::EllipsisLiteral(_) => Self::EllispsisLiteral,
+            ast::Expr::EllipsisLiteral(_) => Self::EllipsisLiteral,
             ast::Expr::Attribute(ast::ExprAttribute {
                 value,
                 attr,