Baum VS Doctrine

Maybe you want to look into the Nested Set pattern: https://en.wikipedia.org/wiki/Nested_set_model. Here is a Laravel package implemeting that: https://github.com/etrepat/baum

If you compare 2.17.x with 2.16.x, you can see quite a few contributions, over a long period of time, and by many different people. Some of them are part of the Doctrine core team, some others are returning contributors, and a few made their very first contribution to that repository. They all do that on their spare time, sometimes after a long day of paid work, take vacations, have a family to take care of. The core team is subscribed to issues, but it's unlikely that contributors are.

(ClassMetadataFactory.php:766 called by ClassMetadataFactory.php:625, https://github.com/doctrine/orm/issues/8893, package doctrine/orm)

Next, I went to see Nicolas Grekas' talk about proxies: he presented different ways to implement a proxy system, and examples of each one that can be found in Symfony or Doctrine. Doctrine has an old implementation in doctrine/common that we are trying to get rid off, and Nicolas has proposed to replace those with Lazy Ghost proxies. I know, I know, funny name. 👻 Lazy ghost proxies cannot be used with final classes, or internal classes, but do allow to use a fluent API, which makes them a good fit for doctrine/orm entities.

Also, since 2.13.0, you get validation at runtime. But it depends on the context I'd say. For instance, for the test suite of doctrine/orm, the best solution is Attributes IMO. When you're doing DDD, XML sounds great!

Solution 3 would be awesome but is far away. A closer term solution 4 could be to make the manager resettable.

It's tracked in this issue: https://github.com/doctrine/orm/issues/9021

You're right, that one doesn't have type hints or phpdoc, I'm not quite sure why.. this one, which is installed in my vendor folder in the demo, does have phpdoc :)

Doctrine