[3.3][DI] Service ids now default to the classname

[wouterj]

Symfony 3.3 has a really nice feature that allows to use the service class as its ID.

Reference: symfony/symfony#21133

[mickaelandrieu]

@wouterj there are 2 ways to resolve this issue:

• if you want to push this practice, we need to update all samples in docs with the "new" way to declare services
• if you don't want to push the practice, a simple note in Dependency Injection component is enough

By the way, as I want to learn a little bit more about "what happens in DI since weeks" I'd like to take this issue :)

[javiereguiluz]

My vote would be for the second option.

[wouterj]

I think the service IDs as class names make sense for one case only: Services that are merely used for it's tag (e.g. custom listener, etc.).

I think we should update all examples that say "Then tag this service with XXX" to use this new behaviour and add a small section about this in the service container subguides, keeping all other service examples just using the new service IDs.

[javiereguiluz]

Closing as fixed because after the latest updates, we always use service injection via autowiring and type-hints and in some cases we show the ->get(Something::class) alternative, so we're always using FQCN ids. The only place where we show old IDs is in the docs explaining how to update from old Symfony to new Symfony and how can you alias services.