Side note: the idea of using the expression language is to have a workaround the current%env()% usage limitation with routes definition.

AFAICT, the service definition is useless for now, as it is not wired in the routing component at all.

I think this doesn't work: reading$_SERVER is not the same as using%env()% (because of env processors + env loaders). People will expect those to be the same.

Instead, I'd suggest to find a way to pre-declare extra key=>value pairs that would be available to conditions (whom values could come from a real%env()% reference from some config file)

We just talked about this on Slack with@HeahDude, I invite you to get in touch with him for details (as he's the one pushing for this to happen :) )

AFAICT, the service definition is useless for now, as it is not wired in the routing component at all.

@stof, It is wired to Routing, there was already a compiler pass that does that
https://github.com/symfony/framework-bundle/blob/master/DependencyInjection/Compiler/AddExpressionLanguageProvidersPass.php#L31