PropertyInfoPropertyMetadataFactory sets writable to false on to-many relations (Doctrine Collection), due to its inability to find the singular-named adder and remover methods - see symfony/symfony#18166; and in SerializerPropertyMetadataFactory we do not change any existing false values on readable/writable, since we cannot know whether it's safe to do so. This leads to incorrect result - basically all to-many relations having writable value of false. (Our functional testing does not catch this because Dummy::relatedDummies is a public property.)

But this is a more general problem. How does a factory decorator know when it's okay / not okay to "overrule" the value set by its predecessor(s)? Does there need to be a confidence value attached? Or even a voting system like that of Symfony Security component? (I'm not sure if I'm going in the right direction...)