Confusion about updating associations dynamically

[thec0keman]

I'm trying to figure out how to dynamically build associations, and I'm a bit confused about the API and what the correct way to handle this is.

My primary use case is we have a complex data model where we need to call multiple traits to set up a variety of associations. These traits can't use associations() though, because we need to generate the association in the context of a specific record (i.e. we need to be able to set foreign keys).

This is an example that I have been working with:

 withQaReports() {
    return this.onCreate(workflow => ({
      ...workflow,
      qualityAssuranceReports: qualityAssuranceReportFactory.buildList(
        2,
        {},
        {
          associations: {
            assignment: assignmentFactory.build({ workflowId: workflow.id }),
          },
        },
      ),
    }));
  }

I'm running into a few issues that either may be my misunderstanding and/or possible bugs:

1. The different lifecycle hooks are confusing. From the documentation, onCreate and afterCreate seem to be specifically for async side-effects. But out of the 3 lifecycle hooks, only onCreate seems to update the factory result from the hook's return value. Is this the intended result / use case? It's just awkward to have to await a factory when I'm not using any async behavior.

2. Chaining traits doesn't seem to work correctly. If I have a factory with multiple traits that update associations via onCreate, only the last called trait will stick. This seems like it is either a bug or I'm not using the hook as intended. I missed in the documentation that onCreate can only be defined once. Given this limitation, this seems like a poor option for my use case.

Is there a way to use composable traits that update the shape of the object?

Thanks!