[BUGFIX beta] Fix createRecord creating two records

[dwickern]

Fixes #5359 and emberjs/ember.js#16258

Explained in #5364:

Before this PR, it was possible to accidentally reify inverse relationships into an invalid state when combining createRecord with @each observers/CPs on an inverse relationship (see test). This would cause internalModel's getRecord to be called recursively with unexpected results. This problem became amplified in Ember 3.x because ArrayProxies now cache the result of objectAt, which lead us to caching the wrong invalid state.

This applies the workaround from #5359 (comment) to create and cache the record before setting any state which might update inverses.

cc @mmun

[mmun]

Thanks @dwickern! Can you also remove the argument and related code from InternalModel#getRecord? It's no longer used.

[mmun]

FYI, the CI failure is unrelated to this PR.

[rwjblue]

Thanks for working on this!

To be clear, this reverts the changes in #4931 which in hindsight were not fully correct. There were still many pathways that would create a model without properties so the reported issue in #4509 was still an issue if you ever used that specific model via normal findRecord / findAll / etc mechanisms (which I daresay is massively more likely than the cases where the user manually calls .createRecord).

I believe this is the correct path forward.

[dwickern]

I'll add that 2 records were being created on ember 2.x as well due to #4931. The extra record was discarded (leaked?) until the ArrayProxy change in ember 3.0 made the behavior visible.

Thanks @mmun for all your work on this!

Do you want a separate PR backporting to ember-data 2.18.x?

[rwjblue]

@dwickern - I think the issues with master should be resolved, would you mind a rebase?

[mmun]

@rwjblue I rebased.

[aaronbhansen]

I'm getting this on Ember 2.18.3. I applied this patch locally and it fixed my problem. @rwjblue @mmun any issue with me opening a PR for this same fix on 2.18?

See this image.

Both order_selection and $E are order/selection models. They have different emberIds, but the same internal model.

My component has a reference to the order_selection from the initial event, but the store has a different model. the order_selection my component is referencing isn't actually found in the store anywhere.

[runspired]

@aaronbhansen this fix introduced other regressions, there would be many, many commits necessary to get the complete fix, as each attempt introduced a new regression I'm not sure it is a good idea for us to attempt to backport this one given there is a relatively easy app-side fix:

let newRecord = store.createRecord(type, props);
newRecord.setProperties(relationships);

[aaronbhansen]

I'll see if that works and update our app code for now. Thanks for the quick response

Update: that did fix the issue for anyone that might be experiencing it on 2.18