Avoid implicit-namespace-package checks for .pyi files (astral-sh#2420)

src/rules/flake8_no_pep420/mod.rs

@@ -13,18 +13,19 @@ mod tests {
     use crate::registry::Rule;
     use crate::settings::Settings;
 
-    #[test_case(Path::new("test_pass_init"); "INP001_0")]
-    #[test_case(Path::new("test_fail_empty"); "INP001_1")]
-    #[test_case(Path::new("test_fail_nonempty"); "INP001_2")]
-    #[test_case(Path::new("test_fail_shebang"); "INP001_3")]
-    #[test_case(Path::new("test_ignored"); "INP001_4")]
-    #[test_case(Path::new("test_pass_namespace_package"); "INP001_5")]
-    fn test_flake8_no_pep420(path: &Path) -> Result<()> {
+    #[test_case(Path::new("test_pass_init"), Path::new("example.py"); "INP001_0")]
+    #[test_case(Path::new("test_fail_empty"), Path::new("example.py"); "INP001_1")]
+    #[test_case(Path::new("test_fail_nonempty"), Path::new("example.py"); "INP001_2")]
+    #[test_case(Path::new("test_fail_shebang"), Path::new("example.py"); "INP001_3")]
+    #[test_case(Path::new("test_ignored"), Path::new("example.py"); "INP001_4")]
+    #[test_case(Path::new("test_pass_namespace_package"), Path::new("example.py"); "INP001_5")]
+    #[test_case(Path::new("test_pass_pyi"), Path::new("example.pyi"); "INP001_6")]
+    fn test_flake8_no_pep420(path: &Path, filename: &Path) -> Result<()> {
         let snapshot = format!("{}", path.to_string_lossy());
-        // Platform-independent paths
         let p = PathBuf::from(format!(
-            "./resources/test/fixtures/flake8_no_pep420/{}/example.py",
-            path.display()
+            "./resources/test/fixtures/flake8_no_pep420/{}/{}",
+            path.display(),
+            filename.display()
         ));
         let diagnostics = test_path(
             p.as_path(),

src/rules/flake8_no_pep420/rules.rs

@@ -20,7 +20,7 @@ impl Violation for ImplicitNamespacePackage {
 
 /// INP001
 pub fn implicit_namespace_package(path: &Path, package: Option<&Path>) -> Option<Diagnostic> {
-    if package.is_none() {
+    if package.is_none() && path.extension().map_or(true, |ext| ext != "pyi") {
         Some(Diagnostic::new(
             ImplicitNamespacePackage(fs::relativize_path(path)),
             Range::default(),

src/rules/flake8_no_pep420/snapshots/ruff__rules__flake8_no_pep420__tests__test_pass_pyi.snap

@@ -0,0 +1,6 @@
+---
+source: src/rules/flake8_no_pep420/mod.rs
+expression: diagnostics
+---
+[]
+