Check newline ending on contents directly (#365)

resources/test/fixtures/W292_2.py

@@ -0,0 +1,2 @@
+def fn() -> None:
+    pass

src/check_lines.rs

@@ -114,10 +114,10 @@ pub fn check_lines(
     }
 
     // Enforce newlines at end of files.
-    if settings.enabled.contains(&CheckCode::W292) {
-        // If the file terminates with a newline, the last line should be an empty string slice.
+    if settings.enabled.contains(&CheckCode::W292) && !contents.ends_with('\n') {
+        // Note: if `lines.last()` is `None`, then `contents` is empty (and so we don't want to
+        // raise W292 anyway).
         if let Some(line) = lines.last() {
-            if !line.is_empty() {
             let lineno = lines.len() - 1;
             let noqa_lineno = noqa_line_for
                 .get(lineno)
@@ -151,7 +151,6 @@ pub fn check_lines(
             }
         }
     }
-    }
 
     // Enforce that the noqa directive was actually used.
     if enforce_noqa {

src/linter.rs

@@ -363,6 +363,18 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn w292_2() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/W292_2.py"),
+            &settings::Settings::for_rule(CheckCode::W292),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn f401() -> Result<()> {
         let mut checks = check_path(

src/snapshots/ruff__linter__tests__w292_2.snap

@@ -0,0 +1,6 @@
+---
+source: src/linter.rs
+expression: checks
+---
+[]
+