Function hasCycleInSchema

packages/core/src/tools/tools.ts:327–405

(schema: object)

 * @returns `true` if a cycle is detected, `false` otherwise.
 */
export function hasCycleInSchema(schema: object): boolean {
  function resolveRef(ref: string): object | null {
    if (!ref.startsWith('#/')) {
      return null;
    }
    const path = ref.substring(2).split('/');
    let current: unknown = schema;
    for (const segment of path) {
      if (
        typeof current !== 'object' ||
        current === null ||
        !Object.prototype.hasOwnProperty.call(current, segment)
      ) {
        return null;
      }
      current = (current as Record<string, unknown>)[segment];
    }
    return current as object;
  }

  function traverse(
    node: unknown,
    visitedRefs: Set<string>,
    pathRefs: Set<string>,
  ): boolean {
    if (typeof node !== 'object' || node === null) {
      return false;
    }

    if (Array.isArray(node)) {
      for (const item of node) {
        if (traverse(item, visitedRefs, pathRefs)) {
          return true;
        }
      }
      return false;
    }

    if ('$ref' in node && typeof node.$ref === 'string') {
      const ref = node.$ref;
      if (ref === '#/' || pathRefs.has(ref)) {
        // A ref to just '#/' is always a cycle.
        return true; // Cycle detected!
      }
      if (visitedRefs.has(ref)) {
        return false; // Bail early, we have checked this ref before.
      }

      const resolvedNode = resolveRef(ref);
      if (resolvedNode) {
        // Add it to both visited and the current path
        visitedRefs.add(ref);
        pathRefs.add(ref);
        const hasCycle = traverse(resolvedNode, visitedRefs, pathRefs);
        pathRefs.delete(ref); // Backtrack, leaving it in visited
        return hasCycle;
      }
    }