[DDC-2196] Improved "extendability" of EntityManager

[mnapoli]

DDC-2196 EntityManager can't be extended easily

EntityManager::create now uses "new static" instead of "new EntityManager"

[doctrinebot]

Hello,

thank you for positing this Pull Request. I have automatically opened an issue on our Jira Bug Tracker for you with the details of this Pull-Request. See the Link:

http://doctrine-project.org/jira/browse/DDC-2197

[mnapoli]

How can I do to avoid the bot to create a new Jira issue for every pull request?

[stof]

you cannot. This is intended as @beberlei prefers to use JIRA to track pending work

[Baachi]

@stof Maybe mark the EntityManager as final?

[mnapoli]

@stof I'm not questioning Jira, it's just that there's already an issue open and I referenced it in the title, but the bot still creates a new (useless) ticket.

@Baachi I think he was refering my question (not the PR)

[Baachi]

@mnapoli You should not extend the EntityManager, because it has some side effects.
And BTW have you looked at #524?

[mnapoli]

@Baachi Thanks I didn't see #514 indeed. So to sum up there is no way to extend the EntityManager, either by inheritance or by decoration?

And I'm curious of what the side effects are?

[beberlei]

@mnapoli we want to prevent fiddiling with the EntityManager API, because its used internally in some places and requires to work exactly that way. We want to prevent weird bugs in user applications this way.