Custom identifiers, no identifier and identifier loaders

[ogizanagi]

Custom identifiers, in a non-Doctrine context.

Since #125, we have potential extension points for loading and defining what represents the identifier in a class.
Something that would have been great, is having a simple property annotation allowing to define which property is the identifier in the class.

Regarding:

The possibility to add an annotation to set our custom idenfier manually without doctrine was removed from this PR and moved in another future PR. Because it imply other changes ... in DataProvider fro example (cant use Doctrine getReference ... DataProvider is really doctrine linked)

I'm not sure I understand the issue, because custom identifiers are not only something needed in the Doctrine context.

Custom (identifier) loaders

On a second hand, currently, we cannot easily add our own loader in the LoaderChain, except using a compiler pass. Is it a sufficient workflow or should we expose more convenient ways to extend this part ?

ValueObject & no identifier

Last but not the least: as stated in #202 (comment):

Also, we should be able to expose resources which do not have an ID. This would be the case for value objects, which may be used for some custom operations.

It's currently impossible, as we get the following exception:

The class "AppBundle\ValueObject\Foo" has no identifier.

A real identifier property does not make any sense for such objects (meant to be used to submit custom payloads with the POST http verb for instance).
But if we really need to have an identifier in ClassMetadata, what about using the same annotation as mentioned above, but on the class, with a value property (default: classname) ?

[dunglas]

How a resource can have an IRI if it has no identifier (value object)?

[ogizanagi]

The point is, to me, that such resources won't need an IRI (but should still appear in the /apidoc), as it only represents custom payloads for operations. However, we don't need an identifier in order to have a resource IRI, but only for item IRIs.

But I'm clearly not an expert of the Json-ld and Hydra vocab, and fail to understand the specifications on many points. My real aim behind this issue is to gather feedbacks and suggestions on how to proceed (and what changes would be necessary in the bundle) in order to expose:

• Custom operations with a given payload, fully documented in the Nelmio api doc and in the /apidoc/contexts using jsonld & hydra vocab:
  • Custom Api Operations might be perfect, except the generated documentation is wrong (Custom payload for custom operation #202), as we cannot specify the resource acting as payload.
  • Exposing directly value object as resources isn't a solution either, as it actually fails because of the missing identifier, and no GET operations (Fix entry point builder #205 (comment)).
• Non-Doctrine resources with a custom identifier (add an identifier loader / generic @Api\Identifier annotation).
• Non-resources objects with no identifiers in general (there are already some issues about it: Handle entities that are not REST resources #166, Problem when using Doctrine Embedded/Embeddable #181).

[teohhanhui]

I don't think it's necessary for a resource to have an IRI if it's only embedded in another resource, e.g. QuantitativeValue

[dunglas]

V2 is now able to deal with non-resource objects.