code: public function getComponentRoot(string $name): ?string
      {
          $rootMap = $this->getConfig('componentsRootMap');
          return isset($rootMap[$name]) ? $this->getAppRoot().$rootMap[$name] : null;
      }
docs: The method returns full path to the parent directory of component by its
  name.
  @param string $name The component name.
  @return string|null