[BUGFIX] fix jsonapi error handling when not using jquery

[aclarembeau]

Fixes #6936

[snewcomer]

A few comments. Also, linting errors are outputted inline. But otherwise will be looking forward to this fix! Thank you!!

[aclarembeau]

@snewcomer , I've updated my code with:

• better respect of linting rules
• updated logic (not parsing JSON payload if payload is not JSON, but an error object)

[ghost]

The asset size checks are failing by 28 bytes; not sure if that amount should hold up this PR.
@runspired thoughts?

[runspired]

Asset size change is totally fine. I agree there is a bug and that the solution is to JSON.parse something.

What I am not convinced of is that this is the right place in the process to do this. To be convinced I need to spend a little time (or Igor needs to spend a little time) walking through the fetch flow and confirming where the point of divergence in behavior occurs so that we are confident we're fixing it at the source and not much later in the flow.

[runspired]

A few comments after reading through the existing implementation:

I believe the necessary change is either this OR

  if (!response.ok) {
    return payload;
  }

^ this line in determineBodyPromise should possibly attempt JSON.parse. I lean heavily towards the former (current PR) solution

The primary difference is in whether we give the adapter the chance to do the parsing. Note the Ajax codepath calls this for all Ajax errors (I'm not sure if a 404 triggers an error though, as odd as that sounds at first glance, it doesn't trigger one in fetch for instance).

But if it does...

let payload = adapter.parseErrorResponse(jqXHR.responseText);

^ this is what would be doing the similar parsing for the Ajax branch.

cc @igorT

[runspired]

I'm approving this for the solution (see comment though for potential alternate solution). I have not reviewed the test changes. cc @igorT

[runspired]

Reviewed tests.