How can test and real components have different dependency graphs?

[suyash192]

Here's a modified version of the component inheritance example from README.md.

@NetworkScope
abstract class NetworkComponent {
    @NetworkScope
    @Provides
    abstract fun api(): Api
}

@Component
abstract class RealNetworkComponent : NetworkComponent() {
    override fun api(depA: DepA): Api = RealApi(depA)
}

@Component
abstract class TestNetworkComponent : NetworkComponent() {
    override fun api(depB: DepB): Api = FakeApi(depB)
}

@Component abstract class AppComponent(@Component val network: NetworkComponent)

Notice that the api() functions in RealNetworkComponent and TestNetworkComponent have different dependencies (DepA and DepB). This will obviously not compile. But in real world situations test classes and prod classes can have different dependencies. How do we achieve this using kotlin-inject?

One solution would be to add all the dependencies to the NetworkComponent.api function signature.

@NetworkScope
@Provides
abstract fun api(depA: DepA, depB: DepB): Api

and then the sub classes can simply ignore the dependency that they don't need. This would work but it feels like a hacky workaround rather than a proper solution. And there might be situations where DepA will be present in main src while DepB will be present in test src.

So what would be the proper solution to this?

[evant]

Does https://github.com/evant/kotlin-inject/blob/main/docs/testing.md answer your question? The README sample was written before that and probably could be updated with a more realistic usecase.

[suyash192]

It does not. These are the classes in testing.md, they have no dependencies, unlike the example I've given above.

    @get:Provides val accountService: AccountService = FakeAccountService(),
    @get:Provides val userService: UserService = FakeUserService(),

[evant]

You want to inject into your test fakes? There's nothing stopping you from declaring extra provides in TestApplicationComponent.

[suyash192]

@evant I'm still unable to understand. AppComponent accepts NetworkComponent in its constructor as it needs the Api dependency declared in it. It does not accept TestNetworkComponent and knows nothing about the additional functions in it. If I add extra provides functions in TestNetworkComponent then they will not be used by AppComponent as it does not know about the additional functions in TestNetworkComponent.

@Component abstract class AppComponent(@Component val network: NetworkComponent)