fix(linter): prevent underflow in count_comment_lines for JSX files

crates/oxc_linter/src/utils/comment.rs

@@ -23,6 +23,92 @@ pub fn count_comment_lines(comment: &Comment, source_text: &str) -> usize {
         if line_has_just_comment(comment_end_line, "*/") {
             end_line += 1;
         }
-        end_line - start_line
+        end_line.saturating_sub(start_line)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use oxc_allocator::Allocator;
+    use oxc_parser::Parser;
+    use oxc_semantic::SemanticBuilder;
+    use oxc_span::SourceType;
+
+    #[test]
+    fn test_count_comment_lines() {
+        let cases: Vec<(&str, SourceType, Vec<usize>)> = vec![
+            // Line comments - standalone
+            ("// This is a comment\nlet x = 1;", SourceType::default(), vec![1]),
+            ("    // This is a comment\nlet x = 1;", SourceType::default(), vec![1]),
+            // Line comments - with code on same line
+            ("let x = 1; // comment", SourceType::default(), vec![0]),
+            // Multiple line comments
+            (
+                "// Comment 1\n// Comment 2\n// Comment 3\nlet x = 1;",
+                SourceType::default(),
+                vec![1, 1, 1],
+            ),
+            // Block comments - single line standalone
+            ("/* comment */\nlet x = 1;", SourceType::default(), vec![1]),
+            // Block comments - single line with code
+            ("let x = /* comment */ 1;", SourceType::default(), vec![0]),
+            // Block comments - empty
+            ("/**/\nlet x = 1;", SourceType::default(), vec![1]),
+            // Block comments - multiline with delimiters on own lines
+            (
+                "/*\n * This is a\n * multi-line comment\n */\nlet x = 1;",
+                SourceType::default(),
+                vec![4],
+            ),
+            // Block comments - multiline with leading whitespace
+            ("    /*\n     * Comment\n     */\nlet x = 1;", SourceType::default(), vec![3]),
+            // Block comments - multiline with start delimiter sharing line with code
+            ("let y = 2; /*\n * Comment\n */\nlet x = 1;", SourceType::default(), vec![2]),
+            // Block comments - multiline with end delimiter sharing line with code
+            ("/*\n * Comment\n */ let x = 1;", SourceType::default(), vec![2]),
+            // Block comments - multiline with both delimiters sharing lines with code
+            ("let y = 2; /*\n * Comment\n */ let x = 1;", SourceType::default(), vec![1]),
+            // JSX comments
+            (
+                r"export function Component() {
+        // hello
+        /*
+        cons
+        */
+  return (
+    <div>
+      {/* hello */}
+      <span>content</span>
+    </div>
+  );
+}",
+                SourceType::tsx(),
+                vec![1, 3, 0],
+            ),
+        ];
+
+        for (source, source_type, expected_counts) in cases {
+            let allocator = Allocator::default();
+            let ret = Parser::new(&allocator, source, source_type).parse();
+            let semantic = SemanticBuilder::new().build(&ret.program).semantic;
+            let comments = semantic.comments();
+
+            assert_eq!(
+                comments.len(),
+                expected_counts.len(),
+                "Expected {} comments in source: {:?}",
+                expected_counts.len(),
+                source
+            );
+
+            for (i, expected_count) in expected_counts.iter().enumerate() {
+                let actual_count = count_comment_lines(&comments[i], source);
+                assert_eq!(
+                    actual_count, *expected_count,
+                    "Comment {i} in source {source:?} expected {expected_count} lines but got {actual_count}",
+                );
+            }
+        }
     }
 }