Merge pull request #2725 from daumantas-kavolis-sensmetry/fix/cursor-previous-sibling

Fix `goto_previous_sibling` with padded first children

cli/src/tests/tree_test.rs

@@ -376,6 +376,45 @@ fn test_tree_cursor() {
     assert_eq!(copy.node().kind(), "struct_item");
 }
 
+#[test]
+fn test_tree_cursor_previous_sibling() {
+    let mut parser = Parser::new();
+    parser.set_language(get_language("rust")).unwrap();
+
+    let text = "
+    // Hi there
+    // This is fun!
+    // Another one!
+";
+    let tree = parser.parse(text, None).unwrap();
+
+    let mut cursor = tree.walk();
+    assert_eq!(cursor.node().kind(), "source_file");
+
+    assert!(cursor.goto_last_child());
+    assert_eq!(cursor.node().kind(), "line_comment");
+    assert_eq!(
+        cursor.node().utf8_text(text.as_bytes()).unwrap(),
+        "// Another one!"
+    );
+
+    assert!(cursor.goto_previous_sibling());
+    assert_eq!(cursor.node().kind(), "line_comment");
+    assert_eq!(
+        cursor.node().utf8_text(text.as_bytes()).unwrap(),
+        "// This is fun!"
+    );
+
+    assert!(cursor.goto_previous_sibling());
+    assert_eq!(cursor.node().kind(), "line_comment");
+    assert_eq!(
+        cursor.node().utf8_text(text.as_bytes()).unwrap(),
+        "// Hi there"
+    );
+
+    assert!(!cursor.goto_previous_sibling());
+}
+
 #[test]
 fn test_tree_cursor_fields() {
     let mut parser = Parser::new();

lib/src/tree_cursor.c

@@ -377,11 +377,15 @@ TreeCursorStep ts_tree_cursor_goto_previous_sibling_internal(TSTreeCursor *_self
   position = parent->position;
   uint32_t child_index = array_back(&self->stack)->child_index;
   const Subtree *children = ts_subtree_children((*(parent->subtree)));
-  for (uint32_t i = 0; i < child_index; ++i) {
-    position = length_add(position, ts_subtree_total_size(children[i]));
-  }
-  if (child_index > 0)
+
+  if (child_index > 0) {
+    // skip first child padding since its position should match the position of the parent
+    position = length_add(position, ts_subtree_size(children[0]));
+    for (uint32_t i = 1; i < child_index; ++i) {
+      position = length_add(position, ts_subtree_total_size(children[i]));
+    }
     position = length_add(position, ts_subtree_padding(children[child_index]));
+  }
 
   array_back(&self->stack)->position = position;