Newly created entity "cannot have a URI as it does not have an ID"

The remote payload that was coming back was missing IDs so there was nothing to map with the Drupal entity IDs. So this error actually makes sense. Sorry for the noise!

This one's back on we've confirmed that it happens even after we're returning the IDs and getting 200 OK.

It's with a Single Storage Client: POSTing/creating is successful, but then there's a WSOD on the front end. Coming at it from another way, GET/fetching data fails (and results in the same WSOD).

If we comment out these lines, it works fine:

So it's coming from ExternalEntityForm->save(), the two toLink() calls.

Set to major as saving is a core feature and it should work.

That was not an easy one. :)

In Drupal, when you use $entity->save() on a new entity, it updates the entity identifier to the new generated value and returns the global constant SAVED_NEW.

With external entities, an entity can come from one or multiple storage clients (sources). When you want to create a new record, a new identifier may be required as input (for example for the "File" storage client) or it can also be optional and generated by the storage client source. To make it more complicated, when you use multiple sources with "foreign keys", you may have to create records in "secondary" sources that may use different identifiers than the one you may provide.

The only way to have it working is to update the new entity identifier after it has been saved on the external sources. This action must be performed by the storage client because it is the one that got the entity, turns it into a raw array and send that array to the remote source. But the remote source must provide back the new identifier! Otherwise there is no generic way to get that new id. For the REST client, we will expect the query used to save the new entry to return the newly saved entity with its new identifier. I've updated the code to have it grab that new identifier and update the corresponding entity identifier. I tested and it appears to work.

What I didn't test yet is if you want to specify an identifier value by yourself. External entities does not allow to provide an identifier on the entity creation form as it follows the default behavior of ContentEntityForm. A work around would be to have another text field "field_specified_id" using the same mapping as the id field and use that field to specify a new id. Not tested though. I wonder what will be the behavior when the raw entity array will be generated: will the "null" value of the id field override the provided value of field_specified_id? I need to check that. There are no rules (or events) at the moment to tell in which order fields should be used to populate a raw entity array. (something to fix one day...)

At the moment, I did not create a corresponding automated test yet. Also, I need to check the other base clients: File storage client and SQL database storage client. And I did not check if the group aggregator handles new id properly when using "foreign keys" (it supposed to as it tricks the entity id for each client).
Meanwhile, I let you test the changes on the issue fork.

Amazing work; thanks!

I took a look at the code and it makes sense. We'll try it here, and get back to you. (I just turned the branch into an MR for easier viewing.)

I have confirmed that the issue has been resolved, and the changes are functioning correctly when a GUID is returned for the ID field after saving. However, it appears that the tests are currently failing, so they may need to be reviewed and updated.

I think we can merge this after tests are passing.

Patch for composer build, until we get this merged

Merging this will require to release a new beta as the API changed since storage clients now need to have a token service to be compatible.
It means existing plugins need to be updated and have a minimum requirement for this new beta (to create).
I'll update the plugins I manage and check for the one I don't. Meanwhile, you can merge.

Hi,
I have the same issue and it persists when i list the external entities.
It seems the entity does not have an id when i try to list them.
To avoid that i propose to set the entity id as you do in the "RestClient->save(), but in the externalEntityStorage->mapRawDataToExternalEntities()

Something like this at the end of the method maybe :

   if ($entities[$id]->id() === NULL) {
        $entities[$id]->set('id', $id);
    }

@guignonv: What do you think? Tests are still passing, so that's good.

Looks good to me. We can merge and see if we got back a similar problem in another use case one day. If it ever happens, we will advise at that time.

Works for me. Merci à tous!