Using the new entityClass option with a custom provider

[mrossard]

API Platform version(s) affected: 3.1.6

Description
I can't get this new option to work as intended while using a custom provider. Either the Get() operation or the GetCollection() is broken.

How to reproduce
https://github.com/mrossard/apip-entityclass

This version gets "The class 'App\ApiResource\DetachedResource' was not found in the chain configured namespaces App\Entity" when you call the Get() operation. Comment the uriVariables: ['id'] and you get `Unable to generate an IRI for the item of type "App\ApiResource\DetachedResource`` on the GetCollection() operation.

Possible Solution
In ApiPlatform\Api\IdentifiersExtractor, if you replace line 136

 throw new RuntimeException('Not able to retrieve identifiers.');

with

return $this->resolveIdentifierValue($this->propertyAccessor->getValue($item, $property), $property);

you seem to get the expected result (on the version without the explicit uriVariables).

[soyuka]

thanks! I'll try to check your reproducer and see if I can fix it :).

[DartCZ]

This solution fixing issue #5502

[SergeyCherenkov]

If the related entity also has an [ApiResource], then I also get Unable to generate an IRI for the item of type.
api-platform/api-platform#2334 (comment)
This solution works, but it still seems to me that this should not be.