extractPolymorphicRelationship method is not called when extracting a polymorphic hasMany relationship

[ehaberev]

Why polymorphic option is checking only for belongsTo relationships when extracting relationships in DS.JSONSerializer (and in DS.RESTSeriazlizer correspondingly)?

I need set proper value for type property in relationship hashes for plymorphic hasMany embedded records (in my case I have @odata.type property in hash and I need to convert it to type property with appropriate value), otherwise error will be thrown in _normalizeEmbeddedRelationship method of DS.EmbeddedRecordsMixin when extracting these relationship hashes.

My serializers are inherited from DS.RESTSerializer, but I can't use neither keyForPolymorphicType hook nor extractPolymorphicRelationship method to specify a custom type key for polymorphic hasMany relationship, because it is called only for belongsTo polymorphic records.

So is there a right way to do this? Or what is a right way to customize extracting polymorphic hasMany relationships (some analogue of extractPolymorphicRelationship method)?

It seems there is no documentation for this case.

[runspired]

Seems like an oversight, feel free to PR a fix.

[Parrryy]

I wouldn't mind picking this up for Hacktoberfest. I'm assuming it's a case of adding the extractPolymorphicRelationship with check to hasMany for each data item?

[runspired]

@Parrryy thanks! and yes:

https://github.com/emberjs/data/blob/v3.3.1/addon/serializers/json.js#L678 here we would make the same conditional branch as the belongs-to based on whether we are polymorphic. I would recommend caching the check for whether we are polymorphic somewhere outside of the loop.