This commit adds a mechanism by which the @angular/core annotations
for @Component, @Injectable, and @NgModule become decorators which,
when executed at runtime, trigger just-in-time compilation of their
associated types. The activation of these decorators is configured
by the ivy_switch mechanism, ensuring that the Ivy JIT engine does
not get included in Angular bundles unless specifically requested.
PR Close#23833
Ivy definition looks something like this:
```
class MyService {
static ngInjectableDef = defineInjectable({
…
});
}
```
Here the argument to `defineInjectable` is well known public contract which needs
to be honored in backward compatible way between versions. The type of the
return value of `defineInjectable` on the other hand is private and can change
shape drastically between versions without effecting backwards compatibility of
libraries publish to NPM. To our users it is effectively an `OpaqueToken`.
By prefixing the type with `ɵ` we are communicating the the outside world that
the value is not public API and is subject to change without backward compatibility.
PR Close#23371
Previously, @Injectable() would generate an ngInjectableDef on the type it was
decorating, even if that type already had a compiled ngInjectableDef, overwriting
the compiled version.
PR Close#22943
This adds compilation of @NgModule providers and imports into
ngInjectorDef statements in generated code. All @NgModule annotations
will be compiled and the @NgModule decorators removed from the
resultant js output.
All @Injectables will also be compiled in Ivy mode, and the decorator
removed.
PR Close#22458
Rename @Injectable({scope -> providedIn}).
Instead of {providedIn: APP_ROOT_SCOPE}, accept {providedIn: 'root'}.
Also, {providedIn: null} implies the injectable should not be added
to any scope.
PR Close#22655
This commit bundles 3 important changes, with the goal of enabling tree-shaking
of services which are never injected. Ordinarily, this tree-shaking is prevented
by the existence of a hard dependency on the service by the module in which it
is declared.
Firstly, @Injectable() is modified to accept a 'scope' parameter, which points
to an @NgModule(). This reverses the dependency edge, permitting the module to
not depend on the service which it "provides".
Secondly, the runtime is modified to understand the new relationship created
above. When a module receives a request to inject a token, and cannot find that
token in its list of providers, it will then look at the token for a special
ngInjectableDef field which indicates which module the token is scoped to. If
that module happens to be in the injector, it will behave as if the token
itself was in the injector to begin with.
Thirdly, the compiler is modified to read the @Injectable() metadata and to
generate the special ngInjectableDef field as part of TS compilation, using the
PartialModules system.
Additionally, this commit adds several unit and integration tests of various
flavors to test this change.
PR Close#22005
