Add regression test for #8108

[Jean85]

As reported in #8108 (comment), this is a regression test for a bug that I encounter when upgrading from ORM 2 to 3. I'm not sure how this should be fixed.

[EDIT] I should add that this doesn't happen if the relation is coming from a trait instead of an abstract class.

[Jean85]

Ok I've debugged the issue, that lies in \Doctrine\ORM\Mapping\Driver\ReflectionBasedDriver::isRepeatedPropertyDeclaration:

• that method should return true, skipping the whole "double-mapping"
• ...but it doesn't because:
  • the reflection says that the property is defined in an (abstract) class which is not declared as an entity (Issue8108WithRelation)
  • while the mapping says that the property is declared in the first entity of the chain (Issue8108Base)

Any suggestion on how we should fix this?

[EDIT] In short, it seems that the issue stems from the fact that I'm having this chain of inheritance:

1. class A (NOT declared as an entity) with a relation / field declared on a property
2. class B extends A, declared as mapped superclass
3. class C extends B, declared as child entity of B

[Jean85]

Bisecting and using this as the reproducer, I've discovered that my chain of inheritance was considered "bad" but accepted in 2.x only thanks to the reportFieldsWhereDeclared set to false.

Should I consider this as invalid and close?

[greg0ire]

I've discovered that my chain of inheritance was considered "bad

By what? The schema validator? If yes, then we should probably close, and I think we might want to work on making it impossible to write regression tests for an invalid schema 🤔

[Jean85]

Locally, the schema validator is what led me to this reproducer, but it's an exception, not a validation error.

This reproducer, ported to the 2.x branch, fails if reportFieldsWhereDeclared is true (with the same exception), passes otherwise. I don't know if it's a validation error or the bug itself, but this is the stack trace:

Doctrine\ORM\Mapping\MappingException: Property "createdBy" in "TmpTest\Issue8108Extending" was already declared, but it must be declared only once                                                         
                                                                                                                                                                                                            
doctrine2/src/Mapping/MappingException.php:395                                                                                                                                     
doctrine2/src/Mapping/ClassMetadataInfo.php:3826                                                                                                                                   
doctrine2/src/Mapping/ClassMetadataInfo.php:3012                                                                                                                                   
doctrine2/src/Mapping/ClassMetadataInfo.php:2980                                                                                                                                   
doctrine2/src/Mapping/Driver/AnnotationDriver.php:619                        
doctrine2/src/Mapping/Driver/AnnotationDriver.php:442                                                                                                                              
doctrine2/src/Mapping/ClassMetadataFactory.php:149                           
doctrine2/vendor/doctrine/persistence/src/Persistence/Mapping/AbstractClassMetadataFactory.php:343                                                                                 
doctrine2/vendor/doctrine/persistence/src/Persistence/Mapping/AbstractClassMetadataFactory.php:207
doctrine2/src/EntityManager.php:318                                                                                                                                                
doctrine2/tests/Tests/OrmFunctionalTestCase.php:381                          
doctrine2/tests/Tests/OrmFunctionalTestCase.php:379                          
doctrine2/tests/Tests/OrmFunctionalTestCase.php:351                                                                                                                                
doctrine2/Issue8108Test.php:32

[greg0ire]

but it's an exception, not a validation error

Then it might be to severe to merely be marked as invalid only to be allowed later on.