Cannot load hasMany relationship for a model with rest adapter combo when overriding findHasMany

[vishwasraj-thyagaraj]

Sample App to reproduce the issue

https://ember-twiddle.com/2f467f447a012edfdfb5600bccfe41c9

Description of the issue

Say a user hasMany tasks

CASE 1 - I can eager load the tasks data along with user
user: { id: 1, name: 'User 1' tasks: [{ id: 1, name: 'Task 1' }] }

and ask the user serialiser.js to deserialise the tasks records

CASE 2 - I can lazy load the tasks data by sending the task id's in user response
user: { id: 1, name: 'User 1' tasks: [1] }

Change async: true in task.js model and this will make N+1 api calls for the tasks id's mentioned

CASE 3 - Load hasMany relationships through pagination

When ever model.tasks is called in a template or route, i expect findHasMany to be triggered where i will set the url to
/users/1/tasks?page=1 and fetch the tasks for that particular page.

{ tasks: [], meta: { count: 100, page: 1, perPage: 10 } }

I found a similar example on one of the blog post, which was suggesting this solution. But the solution doesn't seem to work
https://emberigniter.com/adding-query-parameters-hasmany-relationship

Debugging the addon

I found that, even after i extend the rest adapter the ember data code flows through jsonapi code
https://github.com/emberjs/data/blob/master/packages/store/addon/-private/system/core-store.ts#L1960

Line number 1960 checks for valid links (resource.links.related) which is not available for the model as it doesn't follow JSON API spec.

I overrode shouldFindViaLink to true on line 1967 to check if it triggers, to my surprise it triggered the findHasMany method of the user adapter

https://github.com/emberjs/data/blob/master/packages/store/addon/-private/system/core-store.ts#L1967

Solution ?

So how do i achieve CASE 3, Am i missing something or is this a bug?

This addon also doesn't work https://github.com/mdehoog/ember-data-has-many-query

Versions

3.18.0

[runspired]

@vishwasraj-thyagaraj findHasMany is only invoked if the link is already present. This is called out in the docs here and has been the subject of long-standing discussion here. It was hoped there would be an RFC presented that cleaned this up but it fell through here.