[CLEANUP beta] Change the way metadata in response is stored on record array

[danmcclain]

The previous implementation of inserting metadata from an ajax response
onto a record array used the store as temporary storage for the metadata
via store._metadataFor and store._setMetadataFor. Although rare, this could
store the wrong value on the record array due to a race condition, as
the metadata was stored based on the query's model's name. This moves
the storing of metadata to AdapterPopulatedRecordArray.loadRecords
since, at the time that that method is called, the payload is present,
so we don't have to use store.{_setMetadataFor,_metadataFor}.
store._metadataFor was only used in
AdapterPopulatedRecordArray.loadRecords, so it is no longer needed
with this new implementation.

[bmac]

Looks good to me. @wecc can your also review this pr?

[danmcclain]

I am planning on opening an additional PR to add links to the record array like meta, do you want me to bring it into this PR? Or keep it separate?

[bmac]

I'd say do it in a separate pr.

[danmcclain]

Ok, I'll wait for this PR to be accepted first, as it will tie into the same loadRecords function 👍

[wecc]

Thanks for the PR @danmcclain!

It's nice to see _metadataFor and _setMetadataFor finally go :) I'm trying to remember why we didn't do this for the 1.13 release/New Serializer API refactor but I'm struggling. I think it was along the lines that we didn't want both records and the payload to "leak" to the array. I'm inclined to suggest to just put meta on the array like we do here but I can see how that might make continued JSON API compliance more verbose.

I'm not gonna block this due to ⬆️, the code is private and easily changed if needed. It's very nice to get rid of _metadataFor and _setMetadataFor acting like a proxy, I'm 👍

Can you prefix the commit with [CLEANUP beta]? (not really a BUGFIX imo)

[danmcclain]

@wecc Updated!

I was thinking the same (just passing payload.meta), but I am actually adding links support on one of our projects and grabbed links off of payload as well. When I open the links PR, I'll discuss the approach I've taken for our project

Thanks

[danmcclain]

I take that back, I never pushed it until now. Updated for real @wecc

[amk221]

I was using @vanadar's temporary solution to get meta for a single record. Since this PR it no longer works. Is there an alternative?

[duizendnegen]

Similar issue, the workaround in #4115 now no longer works.

[amk221]

@duizendnegen hack:

// models/base.js
_meta: computed(function() {
  return this._internalModel.type.____meta;
}).volatile()

// serializers/application.js
extractMeta(store, typeClass) {
  let meta = this._super(...arguments);
  typeClass.____meta = meta;
  return meta;
},

// usage
myModel.get('_meta');