[ActiveStorage] url_for returns path, not URL

[jacobsmith]

• I'm not sure if this is a bug, me not understanding the API, or something in between. If it is found to be a bug, I'd be happy to work on a PR if some direction can be given as to how to handle what would be a breaking API change.

Steps to reproduce

Call url_for on an active storage object ( url_for(user.avatar) )

Expected behavior

The returned string will be a fully qualified URL. ( eg. https://myserver.com/rails_storage/blob/foobar )

Actual behavior

Only the path is returned:

/rails_storage/blob/foobar

System configuration

Rails version: 5.2.0

Ruby version: 2.3.3p222

[georgeclaghorn]

This is a documented quirk of url_for:

Note that by default :only_path is true so you'll get the relative “/controller/action” instead of the fully qualified URL like “example.com/controller/action”.

To generate a fully-qualified URL, use polymorphic_url(user.avatar).

[jacobsmith]

Ah, thank you @georgeclaghorn ! I missed that in the documentation somehow. 👍

[dvanoni]

Would it be worthwhile to add a note about this to the Active Storage Overview guide page?

I believe a note about this could be beneficial for those (like myself) using Rails as an API. When returning a JSON response with a URL to a file, a fully-qualified URL probably makes the most sense. It took me a while to hunt down this issue and realize I needed to use polymorphic_url instead of url_for as the guide describes.

[michelson]

It seems rails 5.2.2 has the oposite default for only_path on url_for , the default is false, so now there is no way to generate relative path for an attachment on url_for unless we set that into the Rails.application.routes.default_url_options

[pastullo]

Very confusing but indeed polymorphic_url will work!

[brunoprietog]

I agree that it would be good to document this in the overview active storage guide.

[unRARed]

thank you! polymorphic_url also worked for me. i agree with brunoprietog this quirk should be added from https://edgeguides.rubyonrails.org/active_storage_overview.html. it seems strange to me that url_for would ever return a path, seems like that would be path_for.