[ty] Autocomplete arguments if in arguments node (#24167)

Glyphack · web-flow · commit 9622285ed008 · 2026-03-26T18:35:30.000+01:00
## Summary Addresses [this comment](astral-sh/ty#3087 (comment)). Fixes astral-sh/ty#3087. I initially did the same ancestor walking check in both places but then I tried to come up with another way that does not iterate multiple times. Since in `add_argument_completions` we are already iterating over node ancestors of the node the cursor is in, we can determine if cursor is in an arguments node. So I did that instead of duplicating the `cursor.covering_node.ancestors() ...` code.  ## Test Plan Added the test case that would panic in debug build without this fix.
diff --git a/crates/ty_ide/src/completion.rs b/crates/ty_ide/src/completion.rs
@@ -1397,10 +1397,14 @@ fn add_argument_completions<'db>(
     cursor: &ContextCursor<'_>,
     completions: &mut Completions<'db>,
 ) {
+    let mut in_arguments = false;
     for node in cursor.covering_node.ancestors() {
         match node {
-            ast::AnyNodeRef::ExprCall(call) => {
-                if call.arguments.range().contains_range(cursor.range) {
+            ast::AnyNodeRef::Arguments(_) => {
+                in_arguments = true;
+            }
+            ast::AnyNodeRef::ExprCall(_) => {
+                if in_arguments {
                     add_function_arg_completions(db, model.file(), cursor, completions);
                 }
                 return;
@@ -5465,6 +5469,21 @@ def test_point(p2: Point):
         builder.build().contains("orthogonal_direction");
     }
 
+    // https://github.com/astral-sh/ty/issues/3087
+    #[test]
+    fn no_panic_argument_completion_before_paren() {
+        let builder = completion_test_builder(
+            r#"
+list[int]<CURSOR>()
+"#,
+        );
+
+        assert_snapshot!(
+            builder.skip_keywords().skip_builtins().skip_auto_import().build().snapshot(),
+            @"<No completions found after filtering out completions>",
+        );
+    }
+
     #[test]
     fn from_import1() {
         let builder = completion_test_builder(
