Data: Polymorphic relationships that are sideloaded do not materialize the relationship the first time they are pushed into the store (unless the relationship has been "primed" with a .get beforehand)

[kjhangiani]

We have a polymorphic relationship with the following approximate structure:

post model:
comments: DS.hasMany('comment') // via mixins/commentable.js

comment model:
commentableType: DS.attr('string'),
commentableId: DS.attr('number'),
commentable: DS.belongsTo('commentable', { polymorphic: true, async: true }),

the response to store.findRecord('post', 1, { include: ['comments'] }) returns:

posts: [{ id: 1 }],
comments: [{ id: 1, commentable_type: 'Post', commentable_id: 1}, { id: 2, commentable_type: 'Post', commentable_id: 1}]

however, store.peekRecord('post', 1).get('comments') is null after this API request completes.

Interestingly, if I first do:

store.findRecord('post', 1) (without an include for comments), then call store.peekRecord('post', 1).get('comments'), this seems to "prime" the relationship so to speak, so that later, if comments are loaded from the API, either via a sideload, or directly from the comments endpoint, this relationship will correctly update.

This doesn't seem to be the case in other hasMany / belongsTo sideload situations - it seems to be due to the polymorphic nature of comments.

Here's a repro twiddle on the latest version of ember-data:

https://ember-twiddle.com/a33872a20ef7b7279c6a6566132564cb?openFiles=controllers.application.js%2C

I also tried the polymorphic PR by @runspired here: https://github.com/emberjs/data/pull/5230 but this did not resolve the issue in our app.

Is this a bug? Is there a workaround?

[Shadowere]

I seem to have the same problem with polymorphic relationships, if anyone's got an idea, workaround or anything.
My relationship is defined as async: true and polymorphic: true
For me, if I just use the Ember Inspector to inspect the relationship before actually trying to use it anywhere (code/template), it loads it (meaning it makes the call at that exact moment).
When I use it first directly from the code/template without inspecting it using the Ember Inspector, it doesn't even trigger a query to the server to get the data, and inspecting it after that just shows me an empty canonnical/currentState for the relationship

[kjhangiani]

FYI, it looks like this is a regression from 2.14.x+, it works in 2.13.2

Here's the same twiddle, with just ember-data version downgraded to 2.13.2
https://ember-twiddle.com/d7f7a847cb0a3e93c4d0c5a8189c1967?openFiles=twiddle.json%2C

[runspired]

This should be resolved now since https://github.com/emberjs/data/pull/5230 landed

[kjhangiani]

@runspired @bmac this is actually not resolved with #5230

@runspired as per our discussion on slack, the polymorphic mixin case is still not working. Here is an updated twiddle using 2.18.2, that still exhibits the same regression:

https://ember-twiddle.com/a33872a20ef7b7279c6a6566132564cb?openFiles=twiddle.json%2C

[runspired]

@kjhangiani ah, I forgot this was the mixin-specific issue

[runspired]

@kjhangiani I added it to my bucket of issues to dig in and add tests for today.

[kjhangiani]

thanks @runspired - I'm interested in seeing how you write the tests when you do so - I wanted to try to write the test cases, but I got a little lost in the codebase, especially for this mixin case

[kjhangiani]

just ran into this footgun again on a different polymorphic model - has there been any movement on this @runspired ?

Just tested [email protected] and the bug still exists: https://ember-twiddle.com/a33872a20ef7b7279c6a6566132564cb?openFiles=twiddle.json%2C

Our workaround is pretty hacky right now but it works

//mixins/commentable.js
export default Mixin.create({
    library: service('library'),

    comments: computed(
        'library.comments.[]',  //library.comments = store.peekAll('comment')
        function() {
            return this.get('library.comments').filterBy('commentableType', this.get('_modelName').classify()).filterBy('commentableId', this.get('intId'));
        }
    ),
})

(basically we use the store to filter by type and id instead of using a hasMany)

[runspired]

@kjhangiani I'd like to get some tests in place for it, easy fix if we have them. It's likely a non-issue on the recordData build version of ember-data, but a test would confirm either way.

[runspired]

We should still add tests for this, but I'm going to close this as ember-data since 3.5 has not had lazy relationships and as such would not exhibit this issue.