235a235fab
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
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