Wrapper for multiple value fields are not affected by states.

I got the same problem in my field collection issue.

@Huelfe. Yes, I'm thinking that now that the remaining issue for your field collection is solely this issue.

This issue is a slightly tricky one. Core doesn't give the right hook to alter that point. I'm investigating the best way to work around/fix this without kitten slaughter. I think I have a functional solution but have to do some testing.

Well I've fixed it I think. Latest dev version and requires a core patch. If using composer you can easily add that to your composer.json. Otherwise manually apply the patch :(.

Note: you can also if using composer just add "enable-patching": true to your composer.json's 'extra' key; in which case the patch will be applied by Field States UI/composer.

Composer is picking up the additional patch defined in field_states_ui/composer.json, but fails to apply the patch since it can no longer be applied. The composer project to apply patches (cweagans/composer-patches) currently has a bug where ignoring patches does not work (#112). As a result, our build server now reports the build is unsuccesful.

Can i suggest either:

1. Remove the patch from the module's composer file and provide documentation for installing the additional patch
2. Update the patch to a version that does apply

Considering projects can use different branches for Drupal, I would prefer option 1.

I was about to do write some tests and do a push to get that patch merged... So I go to the logical tests file and ah what?! There's a test for hook_field_widget_multivalue_form_alter. That sure didn't exist. Takes a look:
added in 8.5.x. So I've closed as duplicate my issue and will be adjusting Field States UI to work with the new hook that got added to core. (I think all I'll have to do is adjust my usage to that name, but I'll test it out).

Implementation adjusted to use the new core hook.