Add a "Save and edit" button to the "Add index" page

I'm not sure if p-neyens is still working on this, but here is a patch for it.

Great, thanks a lot!
Already looks quite good, I just had some style changes. Patch attached.

Also, there are a few other changes I'd like to discuss before committing:
- First off, it would be great if we could add a test for this. Maybe just in the IntegrationTest use this button when creating an index.
- The "Delete" button/link has some special code to keep the destination GET parameter intact. Should we add that here, too?

Hello,

I've added a test for this button in IntegrationTest like you mentioned.

For the destination issue, I'm not sure if this is the case. I tried to apply the same logic as for delete, but since the entity is not created yet i could not get the "fields" url in a clean way. In your patch i saw you changed

$form_state->setRedirect('entity.search_api_index.fields', array('search_api_index' => $this->getEntity()->id()));

with $form_state->setRedirectUrl($this->getEntity()->urlInfo('fields'));

Should i use for destination the first approach ? Or do you know something better ?

Sorry for that, for some reason i can't run tests for Search API on my local machine because PHP crashes.
Hope this new patch will do the trick.

Thanks for the additional work!

Should i use for destination the first approach ? Or do you know something better ?

Ah, let's just forget about the destination there. I don't think a redirect after creating an index is as much of a use case as after deleting it.

I think the bug in the test was that you do a drupalPostForm() on the current page (which is the old index's view page) instead of on the "Add index" page. Revised patch attached, hopefully this one will work.

Thanks, looks good to me now.
Not sure why the test did not run, but after it passes i will mark it reviewed.

Good to go

Great, committed.
Thanks again!