Function getElementServiceIfAvailableForDoc

src/element-service.js:83–115

(
  element,
  id,
  extension,
  opt_element
)

 * @return {!Promise<?Object>}
 */
export function getElementServiceIfAvailableForDoc(
  element,
  id,
  extension,
  opt_element
) {
  const s = getServicePromiseOrNullForDoc(element, id);
  if (s) {
    return /** @type {!Promise<?Object>} */ (s);
  }
  const ampdoc = getAmpdoc(element);
  return ampdoc
    .whenExtensionsKnown()
    .then(() => {
      const version = ampdoc.getExtensionVersion(extension);
      if (!version) {
        return null;
      }
      const extensions = getService(ampdoc.win, 'extensions');
      return extensions.waitForExtension(extension, version);
    })
    .then((ext) => {
      if (!ext) {
        return null;
      }
      // If this service is provided by an element, then we can't depend on
      // the service (they may not use the element).
      if (opt_element) {
        return getServicePromiseOrNullForDoc(element, id);
      }
      return getServicePromiseForDoc(element, id);
    });
}

/**
 * Returns a promise for service for the given id in the embed scope of