IdentifierCollectionInterface should extend CollectionInterface

[OskarD]

I am building an extension to this library and to see if a resource's data contains an item or collection, I have to do this:

is_a($resource, IdentifierCollectionInterface::class) || is_a($resource, CollectionInterface::class);

They both extend AccessInterface, so this should have no affect on functionality

[OskarD]

It seems I had an outdated version that had CollectionInterface instead of the more recently added ElementInterface, but the result should be the same

[Art4]

The data attribute in the root Document cannot contain an IdentifierCollectionInterface. This would harm the JSON API spec. A collection in Document can only be a CollectionInterface, so you have to check only is_a($resource, CollectionInterface::class);

See the docs for possible values in Document: https://github.com/Art4/json-api-client/blob/master/docs/objects-document.md#properties

[OskarD]

I understand. Thank you :)

[Art4]

You're welcome. 😊