Capturing cache metadata from file_create_url?

Question

I'm writing a Drupal 8 controller which takes in a media entity, and returns a redirect response to the actual file URL.

It works by finding the file associated with the media entity, and then does this:

      $url = file_create_url($file->getFileUri());

      $response = new CacheableRedirectResponse($url);
      $response->addCacheableDependency($media);
      $response->addCacheableDependency($file);

      return $response;

However, this results in a LogicException: "The controller result claims to be providing relevant cache metadata, but leaked metadata was detected"

Ok, so what's happening is that file_create_url() ends up generating cache metadata, and that cache metadata is not being attached the response object. But it doesn't seem possible for me to do that, because file_create_url just returns a string and not the cache metadata object.

Here's my current workaround, but I'm not sure if this is correct either:

      $context = new RenderContext();
      $url = \Drupal::service('renderer')->executeInRenderContext($context, function () use ($file) {
        return file_create_url($file->getFileUri());
      });

      $response = new CacheableRedirectResponse($url);
      $response->addCacheableDependency($media);
      $response->addCacheableDependency($file);
      if (!$context->isEmpty()) {
        $metadata = $context->pop();
        $response->addCacheableDependency($metadata);
      }

      return $response;

Anyone with more experience with cache metadata know if this is the correct way to handle this situation?

Thank you

Answer 1

This code seems to be OK to me until file_create_url() is transformed into a service which can handle cacheable metadata like UrlGenerator.

An easier way to avoid this error message would be to return an uncacheable RedirectResponse:

  $url = file_create_url($file->getFileUri());
  $response = new RedirectResponse($url);
  return $response;