fix Semantic auto completion fails on lines preceding comments #4552

pyrefly/lib/state/lsp.rs

@@ -4344,13 +4344,20 @@ impl<'a> Transaction<'a> {
         let source = module.lined_buffer().contents();
         let mut offset = TextSize::from(0);
 
-        for line in source.lines() {
+        for line_with_ending in source.split_inclusive('\n') {
+            let line_without_lf = line_with_ending
+                .strip_suffix('\n')
+                .unwrap_or(line_with_ending);
+            let line = line_without_lf
+                .strip_suffix('\r')
+                .unwrap_or(line_without_lf);
             if let Some(comment_pos) = pyrefly_python::ignore::find_comment_start_in_line(line) {
                 let comment_start = offset + TextSize::from(comment_pos as u32);
                 let comment_end = offset + TextSize::from(line.len() as u32);
                 ranges.push(TextRange::new(comment_start, comment_end));
             }
-            offset += TextSize::from((line.len() + 1) as u32);
+            offset += TextSize::try_from(line_with_ending.len())
+                .expect("source line length must fit in TextSize");
         }
 
         ranges

pyrefly/lib/test/lsp/completion.rs

@@ -3765,6 +3765,32 @@ x = sys.version
     );
 }
 
+#[test]
+fn completion_before_comment_with_crlf_line_endings() {
+    let code = concat!(
+        "class Foo:\r\n",
+        "    x: int\r\n",
+        "foo = Foo()\r\n",
+        "foo.\r\n",
+        "# comment\r\n",
+    );
+    let (handles, state) = mk_multi_file_state(&[("main", code)], Require::Exports, false);
+    let handle = handles.get("main").unwrap();
+    let position = TextSize::try_from(
+        code.find("foo.\r\n").expect("completion line must exist") + "foo.".len(),
+    )
+    .expect("completion position must fit in TextSize");
+    let completions =
+        state
+            .transaction()
+            .completion(handle, position, ImportFormat::Absolute, true, None);
+
+    assert!(
+        completions.iter().any(|item| item.label == "x"),
+        "Expected attribute completions before a comment, got {completions:?}"
+    );
+}
+
 #[test]
 fn completion_sorts_incompatible_call_argument_last() {
     let code = r#"