Crash when referenced item id does not exist.

[Dragomir-Ivanov]

Using the common example case:

PUT http://localhost:8080/api/users/bgl8mqh40fmepk0u53kg
POST http://localhost:8080/api/users/bgl8mqh40fmepk0u53kg/posts
DELETE http://localhost:8080/api/users/bgl8mqh40fmepk0u53kg
GET http://localhost:8080/api/posts?fields=user{id,name}

The last GET crashes rest-layer. I traced down to:

// MultiGet implements query.Resource interface.
func (r restResource) MultiGet(ctx context.Context, ids []interface{}) ([]map[string]interface{}, error) {
	items, err := r.Resource.MultiGet(ctx, ids)
	if err != nil {
		return nil, err
	}
	payloads := make([]map[string]interface{}, 0, len(items))
	for _, i := range items {
		payloads = append(payloads, i.Payload)
	}
	return payloads, nil
}

where i is nil.
Managed to somewhat workaround with:

		if i != nil {
			payloads = append(payloads, i.Payload)
		} else {
			payloads = append(payloads, nil)
		}

However, now user is returned as:

[{
  "_etag": "ecfdfa0ab4f3d63f0133c121ee7bf047",
  "user": {}
}]

Where ideally for me to be "user": null. What is your advice @smyrman @rs .Thanks.

[smyrman]

This is a side effect of there being no Cascade delete in MongoDB. Arguably, Cascade delete is not always what you want though.

For similar cases, we have a custom hook that remove dead references before returning some objects, also when not expanded, if I remember correctly.

Other then that, "user": null sounds reasonable to me.

[Dragomir-Ivanov]

Thanks! Actually I don't care about cascading deletes, just want for rest-layer not to crash if such use case happens. Will try to fix "user": null issue.