Function visit

src/language/visitor.ts:261–384

(
  root: ASTNode,
  visitor: ASTVisitor | ASTReducer<any>,
  visitorKeys: ASTVisitorKeyMap = QueryDocumentKeys,
)

 * @internal
 */
export function visit(
  root: ASTNode,
  visitor: ASTVisitor | ASTReducer<any>,
  visitorKeys: ASTVisitorKeyMap = QueryDocumentKeys,
): any {
  const enterLeaveMap = new Map<Kind, EnterLeaveVisitor<ASTNode>>();
  for (const kind of Object.values(Kind)) {
    enterLeaveMap.set(kind, getEnterLeaveForKind(visitor, kind));
  }

  /* eslint-disable no-undef-init */
  let stack: any = undefined;
  let inArray = Array.isArray(root);
  let keys: any = [root];
  let index = -1;
  let edits = [];
  let node: any = root;
  let key: any = undefined;
  let parent: any = undefined;
  const path: any = [];
  const ancestors = [];
  /* eslint-enable no-undef-init */

  do {
    index++;
    const isLeaving = index === keys.length;
    const isEdited = isLeaving && edits.length !== 0;
    if (isLeaving) {
      key = ancestors.length === 0 ? undefined : path[path.length - 1];
      node = parent;
      parent = ancestors.pop();
      if (isEdited) {
        if (inArray) {
          node = node.slice();

          let editOffset = 0;
          for (const [editKey, editValue] of edits) {
            const arrayKey = editKey - editOffset;
            if (editValue === null) {
              node.splice(arrayKey, 1);
              editOffset++;
            } else {
              node[arrayKey] = editValue;
            }
          }
        } else {
          node = { ...node };
          for (const [editKey, editValue] of edits) {
            node[editKey] = editValue;
          }
        }
      }
      index = stack.index;
      keys = stack.keys;
      edits = stack.edits;
      inArray = stack.inArray;
      stack = stack.prev;
    } else if (parent != null) {