Support @singleton annotation

[mikeki]

Expected Behavior

Other IoC libraries have support for the @singleton annotation which indicates that an @injectable class will always resolve inSingletonScope.

I think having support for this annotation would be extremely helpful for my team, and other teams that use inversify.

Current Behavior

Currently it is necessary to create a binding just to mark a class as Singleton, but being singleton is such a core aspect of dependency injection.

[carlossalasamper]

Hi! If you are using mostly singleton scope dpeendencies in a container you can pass the option defaultScope to the container when you create it:

const container = new Container({ defaultScope: 'Singleton'})

[mikeki]

Thank you @carlossalasamper, not all of my injections are singletons, but I was poking around and found https://github.com/inversify/inversify-binding-decorators which allows to create the annotation I needed

IMO we should just get that project as part of the main InversifyJS project too

[notaphplover]

Hey @mikeki, I'm giving some love to the project these days. I think it's a great idea, I totally agree with you.

I would implement this as an option in the @injectable decorator:

@injectable({
  scope: BindingScope.Singleton,
})
class Foo {}

I'm working on internal refactors and it's my current priority after solving issues, but once I finish it I would love to implement this feature.