Async in prod and debug version does not perform the same

[cbou]

Because of the use of assert in the debug version of EmberJS Data, when using relationship with async: false the records needs to be loaded before using the relationship.

In the prod version, the assert is not present which is allow to the relationship even if the related record is not loaded yet. It will be updated as soon as the record is loaded.

To me the assert should be changed into a warn.

https://github.com/emberjs/data/blob/master/addon/-private/system/relationships/state/belongs-to.js#L143
https://github.com/emberjs/data/blob/master/addon/-private/system/relationships/state/has-many.js#L207

[fivetanley]

Hi Charles,

Is it just that it's confusing that it's an error in development but allowed in production? Maybe we should change it to always throw?

[cbou]

No please don't do this!

It's actually quite useful because sometimes the related record is loaded after.

[pangratz]

It's actually quite useful because sometimes the related record is loaded after.

@cbou I would say if you explicitly mark a relationship as synchronous via { async: false } but sometimes the record is loaded after, you should treat your relationship as asynchronous. Otherwise side effects cannot be ruled out and this might result in unexpected behavior.

Any reason you're not using asynchronous relationships here?

[cbou]

I used { async: false } to prevent EmberJS loading some models.

The reason is that I have some models which are loaded and updated outside of EmberJS. I keep them sync using store.pushPayload. I still defined these mixed models inside EmberJS in order to use them there (read only) and they are linked to other models which are loaded and updated in EmberJS.

[pangratz]

I used { async: false } to prevent EmberJS loading some models.

Relationships are only loaded if they are explicitly requested... Maybe there is some code in your application which triggers loading of relationships as a side effect.

Can you provide some sample code / ember-twiddle demonstrating your use case?

[cbou]

I request them in the templates when calling {{a.b.name}} and if the relationship is not loaded, I don't want EmberJS to load it. I want to have an empty name first until it's pushed from the other part of the app.

[pangratz]

Hmm, I don't know of any easy solution to that at the moment 😔

References added in #3303 allow you to check the loading state of relationships without triggering a fetch, but they are currently not available in templates...

[cbou]

For the moment it's fine as long as an error is not throw in production like @fivetanley suggested.

It would be better if assert could be changed in warn but it's a nice to have.

[runspired]

Closing this as a duplicate of #5226