feat(injector): implement a different approach to injector scopes

[rodyhaddad]

An easy way to review this is to read the tests and see if that's what we want

[rodyhaddad]

This PR makes this test pass (discussed with vojta, having this test pass is not set in stone):

it('should do stuff and work', function () {
  class RouteScope extends ScopeAnnotation {}

  function Compiler() {}

  @Inject(Compiler)
  function Foo(compiler) {
    this.compiler = compiler;
  }

  @RouteScope
  @Inject(Foo, Compiler)
  function RequestHandler(foo, compiler) {
    this.foo = foo;
    this.compiler = compiler;
  }

  @Provide(Compiler)
  function RouteCompiler() {}


  var injector = new Injector(),
    child = injector.createChild([RouteCompiler], [RouteScope]);

  var reqHandler = child.get(RequestHandler);

  expect(reqHandler.compiler).not.toBe(reqHandler.foo.compiler);
  expect(reqHandler.compiler).toBeInstanceOf(RouteCompiler);
  expect(reqHandler.foo.compiler).toBeInstanceOf(Compiler);
});

I'll amend the PR to add this test if that's the behavior that we want.

[vojtajina]

Let's call it Scope to make it consistent. Or DefaultScope, BaseScope or something?

I think you are right and we might rename all of the annotations to *Annotation but that can be done in a separate commit. The reason why I didn't do that already was that then people have to import it as import {InjectAnnotation as Inject} from 'di';... and that kind of sucks....

We should probably separate all these annotations to a separate module because often projects only need the annotations (so that their code can be used with DI) but they don't need the actual DI. Then, I think Inject, Scope, etc. will be fine...

What do you think?

[vojtajina]

@rodyhaddad this is awesome. Thank you! I left some subtle comments, nothing serious...

[vojtajina]

Can you change this fancy indentation to:

var a = b;
var c = d;
var e = f;

I know we use this in Angular codebase, but I prefer this old-school style, it's much easier to add new var or re-order...

[vojtajina]

Same for other places....