DCOM-287: [GH-369] [RFC] Load parent classes when loading metadata from cache

[doctrinebot]

Jira issue originally created by user @doctrinebot:

This issue is created automatically through a Github pull request on behalf of gonzalovilaseca:

Url: doctrine/common#369

Message:

This can be done more neatly, but before putting more time in it I'd like to check if it's a good idea.
I came across this solution because we had a problem with Gedmo extensions when caching metadata in Redis, this is our scenario:

Class A extends B;

Class B has a Gedmo extension mapped field.

On first request metadata for both Class A and Class B is cached in Redis.

On second request AbstractClassMetadataFactory loads Class A from Redis.

Gedmo extension loops through all Class A parents and calls method hasMetadataFor($parentClass) in AbstractClassMetadataFactory, only Class A metadata has been loaded previously, therefore hasMetadataFor($parentClass) returns false, and Gedmo then skips the parent class.

Should Gedmo exension load the metadata for the parent class or should it be done as proposed in this PR?

[doctrinebot]

Comment created by gvf:

Have you had the chance to look at this issue? thnxs.