TSNode ts_node_child_by_field_id()

in lib/src/node.c [503:567]

• 47 lines of code
• 16 McCabe index (conditional complexity)

TSNode ts_node_child_by_field_id(TSNode self, TSFieldId field_id) {
recur:
  if (!field_id || ts_node_child_count(self) == 0) return ts_node__null();

  const TSFieldMapEntry *field_map, *field_map_end;
  ts_language_field_map(
    self.tree->language,
    ts_node__subtree(self).ptr->production_id,
    &field_map,
    &field_map_end
  );
  if (field_map == field_map_end) return ts_node__null();

  // The field mappings are sorted by their field id. Scan all
  // the mappings to find the ones for the given field id.
  while (field_map->field_id < field_id) {
    field_map++;
    if (field_map == field_map_end) return ts_node__null();
  }
  while (field_map_end[-1].field_id > field_id) {
    field_map_end--;
    if (field_map == field_map_end) return ts_node__null();
  }

  TSNode child;
  NodeChildIterator iterator = ts_node_iterate_children(&self);
  while (ts_node_child_iterator_next(&iterator, &child)) {
    if (!ts_subtree_extra(ts_node__subtree(child))) {
      uint32_t index = iterator.structural_child_index - 1;
      if (index < field_map->child_index) continue;

      // Hidden nodes' fields are "inherited" by their visible parent.
      if (field_map->inherited) {

        // If this is the *last* possible child node for this field,
        // then perform a tail call to avoid recursion.
        if (field_map + 1 == field_map_end) {
          self = child;
          goto recur;
        }

        // Otherwise, descend into this child, but if it doesn't contain
        // the field, continue searching subsequent children.
        else {
          TSNode result = ts_node_child_by_field_id(child, field_id);
          if (result.id) return result;
          field_map++;
          if (field_map == field_map_end) return ts_node__null();
        }
      }

      else if (ts_node__is_relevant(child, true)) {
        return child;
      }

      // If the field refers to a hidden node, return its first visible
      // child.
      else {
        return ts_node_child(child, 0);
      }
    }
  }

  return ts_node__null();
}