Don't serialize new has many relationships

[ryanto]

Similar to #5317 but for hasMany.

Currently when saving a model with an unsaved hasMany a null id is used in the JSON:API document.

For example

let company = this.store.peekRecord('company', 1);

let user = this.store.createRecord('user');
company.get('users').addObject(user);

company.save();

Generates this post payload (note that we're using serializer option attrs.users.serialize = true)

{
  data: {
    type: 'company',
    id: '1',
    relationships: {
      users: [
        data: {
          type: 'users',
          id: null
        }
      ]
    }
  }
}

This is an invalid payload. To fix this, we'll filter out new records from using in the serialized belongsTo.

[bmac]

lgtm

[sly7-7]

Looks good if we don't want to automatically save the new record.
I just wonder in that scenario if we could add an option to send the newly created user together with the company. Not sure it that even makes sense.

[ryanto]

@sly7-7 Yup! I think you're describing a common use case for most applications would want. I'm expecting JSONAPI operations to be the answer to that problem: json-api/json-api#1254

[runspired]

@ryanto not super sure why this failed CI. Could you rebase and let it kick off again?

[ryanto]

All set, I'll keep an eye on CI.

FYI when I pulled the latest and ran yarn install it looks like it added an entry to the lockfile.

[runspired]

victim of a timeout, restarted tests again

[runspired]

Thanks @ryanto !

[juggy]

There is problem with this bug fix. An empty relationship is not serialized anymore, which is a different behavior than before. @runspired @ryanto

If you have a relation and remove it and save the record, to inform the backend of that relation change, you need to send that empty array back.

[ryanto]

@juggy Yikes! Sorry about that.

Could you give me a failing test case, or even some example HTTP request/responses with what you expect vs what Ember Data is doing?

[juggy]

Well the format should be the one of 3.1...

...
"relationships": {
  "my_relations: {
    "data": []
  }
}

[ryanto]

PR is here: #5466

[ryanto]

@juggy A fix has been merged, let me know if you run into any other issues.