RESTSerializer.serializePolymorphicType broken for async relationships

[martinmaillard]

When a relationship is defined as polymorphic and async, serializePolymorphicType raises key is undefined because the related object is wrapped in a promise, which breaks belongsTo.constructor.typeKey.

[martinmaillard]

I just noticed that polymorphic was not listed as a valid option for belongsTo in the docs. Is it not supported anymore ?

[bmac]

I suspect the fact that polymorphic is missing in the belongsTo docs is a doc bug.

[bmac]

@martinmaillard it seems like you have a good understanding of the problem and this definitely seems like a bug. Would you be comfortable submitting a pr to fix this issue with a test case?

[martinmaillard]

I'll see what I can do once I've checked how the new beta version behaves. I'm not sure I've got such a good understanding of the internals yet...

[martinmaillard]

I started writing the tests for this issue and it made me realize that I don't know what the normal behavior should be. I see two cases for an async belongsTo:

• the related record is already loaded
• the related record is not loaded yet

In the first case, the record can be extracted from the promise and the polymorphicType property can be serialized as usual.

In the second case, I'm not sure. It does not seem like a good idea to load the record just to serialize its parent. Can we access the original payload of the parent record and extract the original polymorphicType property from it ?

[martinmaillard]

Sooooo, it seems like this problem is not new at all (#1491), and a lot of work has already been done (#1535). I don't really understand why the PR is closed though...

[chadhietala]

I believe this is also related #2342 (comment)

[sly7-7]

@martinmaillard Hm, I didn't get the bug in #1535 was because of polymorphism, and I thought it was just a matter of async relation, which seem to work, considering this test passes.
I don't know if I will have time this week end, but I will try to at least write a failing test about your issue (async polymorphism relation), and will see if the suggestion in #1491 will fix this issue.

@chadhietala #2342 seems yet an other one, caused by polymorphism and MODEL_FACTORY_INJECTION, which I think basically broke polymorphism in ember-cli app.

[luketheobscure]

Here's a hacky workaround in CoffeeScript... but it requires you to make sure that the async is fulfilled before you try to serialize it.

 serializePolymorphicType: (record, json, relationship) ->
    key = relationship.key
    belongsTo = record.get(key)
    # hack for async
    if belongsTo.constructor == DS.PromiseObject
      if belongsTo.get('isFulfilled')
        belongsTo = belongsTo.get('content')
      else
        throw Error("Unable to get belongsTo for relation that isn't fulfilled")
    key = if @keyForAttribute then this.keyForAttribute(key) else key
    if Ember.isNone(belongsTo)
      json[key + "_type"] = null
    else
      json[key + "_type"] = Ember.String.classify(belongsTo.constructor.typeKey)

[igorT]

Should be fixed by #2623