Currently, when you want to inject all services with a specific tag you have to write your own compiler pass as described here. Additionally, one has to use method calls instead of injecting the services into the constructor because obviously the parameter cannot be inferred.

It would be handy if there was a way to inject all services that are tagged with a specific tag, optimally indexed by their id:

Foo\Bar:
    arguments:
        - '@doctrine.orm.entity_manager'
        - '@=taggedServices("my_tag")'

Resulting in:

[
    "Foo\Service1" => Foo\Service1 {...},
    "Foo\Service2" => Foo\Service2 {...},
]

This is probably not an everyday use-case but maybe other people would be interested in this.