Add inject service RFC

[mydea]

Rendered

[kpfefferle]

This may seem like a good idea in isolation, but it breaks down a bit in the greater context. A couple of immediate issues that I can see with directly renaming inject to service:

1. The default export from the @ember/service module is typically named Service (as it's the base class to extend when creating a service). If you're injecting a service into a service, you'll end up with a import statement that looks something like this that's likely to cause confusion:

   import Service, { service } from '@ember/service';
   

2. The name of an export like inject also needs to make sense internally within the @ember/service module. This is the primary reason why inject is the most logical name for both Service and Controller inject functions - because that naming describes exactly what they do.

I have had some apps I've worked on where both inject functions are imported into the same file (though IMO Controller injections should generally be avoided). In these cases, I rename them to injectController and injectService instead of controller and service. If we really want to push to rename the exported functions so that we can avoid renaming them on import (which has not really been a pain point for me personally), then maybe injectController and injectService would be better naming choices as they'd satisfy both of the above concerns?

[NullVoxPopuli]

that looks something like this that's likely to cause confusion:

I don't think this'll cause confusion

I'm in favor of this RFC -- a very much don't like renaming the import as a default for convention's sake. It'd be fantastic to just import service

[NullVoxPopuli]

though, it might make more sense to have

import { service } from '@ember/application';

[pzuraq]

Personally, I think that decorators should describe what they provide, not how they provide it. @inject is a verb, it's an action that we take at a specific point in time. In declarative programming, we want to avoid describing values imperatively. @service describes what the value is, and how it should be thought of when used.

I also don't think the overlap between injecting controllers and services should matter much. Controllers will eventually be deprecated, along with controller injections, so we should be focusing on the future of dependency injection without them, which will likely consist of only services.

[chriskrycho]

@kpfefferle a couple notes in response here:

1. While it's true that you could have confusion from import Service, { service } from '@ember/service';, I suspect the vast majority of injections aren't in other services, but in components etc. And of course you can still rename if it's helpful in that case!

2. There's zero reason—literally none!—that the name used internally and the exported name need to be the same. To the contrary! A module can and should use whatever name makes the most sense internally, and then export for its public API the name that makes sense for consumers. JS supports this as a language level feature!

   export { inject as service };

[mydea]

I personally have always been using

import Service, { service } from '@ember/service';

when I needed another service inside of a service and never found it confusing.

I also never inject controllers, I just notice it every time I type @inject in my editor to get auto-completion and always get two different imports with the same name proposed, having to look closely at the import path in order to pick the correct one. (only to then go in and manually alias the import)

[chancancode]

This was discussed at today's framework team meeting and we think this is ready for Final Comment Period!

[mixonic]

I've pushed a notable update here. It:

• Makes the 5.0 deprecation timeline for inject explicit.
• Adds prose about how addons need to handle this adjustment.

[rwjblue]

Thank you!!!

[buschtoens]

Thanks for working on this RFC! I'm happy to see it merged.

With regards to addon interoperability with older Ember versions, I was wondering whether we could provide a polyfill instead of requiring addon authors to spell out:

import * as ES from '@ember/service';
const service = ES.service ?? ES.inject;

In old globals-resolver-based apps we could probably leverage babel-plugin-ember-modules-api-polyfill. In apps using the modules API and / or embroider, we probably need some other mechanisms, e.g. macros or import maps.

[mehulkar]

I see a bunch of comments in here about deprecating controller injections and just wanted to share #574 again. Feel free to resurrect.