Function focusWithin

packages/react-reconciler/src/ReactTestSelectors.js:506–543

(
  hostRoot: Instance,
  selectors: Array<Selector>,
)

}

export function focusWithin(
  hostRoot: Instance,
  selectors: Array<Selector>,
): boolean {
  if (!supportsTestSelectors) {
    throw new Error('Test selector API is not supported by this renderer.');
  }

  const root = findFiberRootForHostRoot(hostRoot);
  const matchingFibers = findPaths(root, selectors);

  const stack = Array.from(matchingFibers);
  let index = 0;
  while (index < stack.length) {
    const fiber = ((stack[index++]: any): Fiber);
    const tag = fiber.tag;
    if (isHiddenSubtree(fiber)) {
      continue;
    }
    if (
      tag === HostComponent ||
      tag === HostHoistable ||
      tag === HostSingleton
    ) {
      const node = fiber.stateNode;
      if (setFocusIfFocusable(node)) {
        return true;
      }
    }
    let child = fiber.child;
    while (child !== null) {
      stack.push(child);
      child = child.sibling;
    }
  }

  return false;
}

const commitHooks: Array<Function> = [];