Start work on exposing APIs for node descendant counts and indices

cli/src/tests/node_test.rs

@@ -385,10 +385,30 @@ fn test_node_named_child_with_aliases_and_extras() {
     assert_eq!(root.named_child(4).unwrap().kind(), "C");
 }
 
+#[test]
+fn test_node_descendant_count() {
+    let tree = parse_json_example();
+    let value_node = tree.root_node();
+    let all_nodes = get_all_nodes(&tree);
+
+    assert_eq!(value_node.descendant_count(), all_nodes.len());
+
+    let mut cursor = value_node.walk();
+    for (i, node) in all_nodes.iter().enumerate() {
+        cursor.goto_descendant(i);
+        assert_eq!(cursor.node(), *node, "index {i}");
+    }
+
+    for (i, node) in all_nodes.iter().enumerate().rev() {
+        cursor.goto_descendant(i);
+        assert_eq!(cursor.node(), *node, "rev index {i}");
+    }
+}
+
 #[test]
 fn test_node_descendant_for_range() {
     let tree = parse_json_example();
-    let array_node = tree.root_node().child(0).unwrap();
+    let array_node = tree.root_node();
 
     // Leaf node exactly matches the given bounds - byte query
     let colon_index = JSON_EXAMPLE.find(":").unwrap();
@@ -841,15 +861,17 @@ fn get_all_nodes(tree: &Tree) -> Vec<Node> {
     let mut visited_children = false;
     let mut cursor = tree.walk();
     loop {
-        result.push(cursor.node());
-        if !visited_children && cursor.goto_first_child() {
-            continue;
-        } else if cursor.goto_next_sibling() {
-            visited_children = false;
-        } else if cursor.goto_parent() {
-            visited_children = true;
+        if !visited_children {
+            result.push(cursor.node());
+            if !cursor.goto_first_child() {
+                visited_children = true;
+            }
         } else {
-            break;
+            if cursor.goto_next_sibling() {
+                visited_children = false;
+            } else if !cursor.goto_parent() {
+                break;
+            }
         }
     }
     return result;