Function getFocusableTreeWalker

packages/react-aria/src/focus/FocusScope.tsx:839–896

(
  root: Element,
  opts?: FocusManagerOptions,
  scope?: Element[]
)

 * that matches all focusable/tabbable elements.
 */
export function getFocusableTreeWalker(
  root: Element,
  opts?: FocusManagerOptions,
  scope?: Element[]
): ShadowTreeWalker | TreeWalker {
  let filter = opts?.tabbable ? isTabbable : isFocusable;

  // Ensure that root is an Element or fall back appropriately
  let rootElement = root?.nodeType === Node.ELEMENT_NODE ? (root as Element) : null;

  // Determine the document to use
  let doc = getOwnerDocument(rootElement);

  // Create a TreeWalker, ensuring the root is an Element or Document
  let walker = createShadowTreeWalker(doc, root || doc, NodeFilter.SHOW_ELEMENT, {
    acceptNode(node) {
      // Skip nodes inside the starting node.
      if (nodeContains(opts?.from, node)) {
        return NodeFilter.FILTER_REJECT;
      }

      if (
        opts?.tabbable &&
        (node as Element).tagName === 'INPUT' &&
        (node as HTMLInputElement).getAttribute('type') === 'radio'
      ) {
        // If the radio is in a form, we can get all the other radios by name
        if (!isTabbableRadio(node as HTMLInputElement)) {
          return NodeFilter.FILTER_REJECT;
        }
        // If the radio is in the same group as the current node and none are selected, we can skip it
        if (
          (walker.currentNode as Element).tagName === 'INPUT' &&
          (walker.currentNode as HTMLInputElement).type === 'radio' &&
          (walker.currentNode as HTMLInputElement).name === (node as HTMLInputElement).name
        ) {
          return NodeFilter.FILTER_REJECT;
        }
      }

      if (
        filter(node as Element) &&
        (!scope || isElementInScope(node as Element, scope)) &&
        (!opts?.accept || opts.accept(node as Element))
      ) {
        return NodeFilter.FILTER_ACCEPT;
      }

      return NodeFilter.FILTER_SKIP;
    }
  });

  if (opts?.from) {
    walker.currentNode = opts.from;
  }

  return walker;
}