function resolveAsset (
  options,
  type,
  id,
  warnMissing
) {
  /* istanbul ignore if */
  if (typeof id !== 'string') {
    return
  }
  var assets = options[type];
  // check local registration variations first
  if (hasOwn(assets, id)) { return assets[id] }
  var camelizedId = camelize(id);
  if (hasOwn(assets, camelizedId)) { return assets[camelizedId] }
  var PascalCaseId = capitalize(camelizedId);
  if (hasOwn(assets, PascalCaseId)) { return assets[PascalCaseId] }
  // fallback to prototype chain
  var res = assets[id] || assets[camelizedId] || assets[PascalCaseId];
  if (warnMissing && !res) {
    warn(
      'Failed to resolve ' + type.slice(0, -1) + ': ' + id,
      options
    );
  }
  return res
}
Resolve an asset.
This function is used because child instances need access
to assets defined in its ancestor chain.