Remove multi-application registration

[lcobucci]

We now support the configuration of different apps within a single DI container. That creates a lot of complexity for no good reason.

By removing this, we'd be able to define "static" services for routers and buses, which makes our lives much simpler.

It's quite important to mention that we should aim at doing this without breaking BC too much (registering aliases for things and still look for parameters using the app name as the prefix).

[rodrigorigotti]

I'm studying a fix for this issue, and the idea I have in mind is as follows:

• We'd still allow the name to be passed to RegisterApplication instead of relying on a default app name (eg, app) to keep BC
• \Chimera\DependencyInjection\RegisterApplication::$name becomes a static property so that in case the application tried to register a second application it throws an exception (since we only allow single-applications registrations)
• We apply the same behaviour on \Chimera\DependencyInjection\Routing\Expressive\RegisterServices and \Chimera\DependencyInjection\Routing\Expressive\Package which also rely on the application name (consequently simplifying the logic inside them, eg when extracting route list or extracting midldeware list)

What do you think?

[lcobucci]

I don't believe we should rely on the user provided name to control that.

On the first run we should register the web application using Chimera\Routing\Application as an alias. If someone tries to register something again we check whether the alias exists or not.

For BC, we'd create an alias for the user provided name (which points to Chimera\Routing\Application).

All the compiler passes we have should use the class names as service ids (and map the interface as aliases), because they will only be registered once. This gives us an opportunity to clean up the dynamic service creation and pull things into the XML files.

Does that make sense to you?

[rodrigorigotti]

Okay, so let me see if I understood correctly: when processing the services for an application we should add a Chimera\Routing\Application alias to it at the very end of this process. This alias would then be present in the container. Because of this, trying to register a second application would cause an exception because the alias already exists.

The second part makes sense since there would be a single instance of each compiler pass since there's only a single application registered. I only have to see what needs to be moved to the XML files but, like you said, we clean up a lot of PHP making the whole service definition a lot easier.

[WyriHaximus]

Have you considered splitting your app up in logistical chunks? For example app with your main app, metrics to expose metrics, and healtz to provide a health check. All of these would serve their domain isolated from the others so you can accidentally export metrics or your health check from your app.