The problem with cyclic injects checker

Hello! Unfortunately, I got an unexpected crash with toothpick.

How to reproduce the crash

val parentScope = KTP.openScope("App")
val childScope = KTP.openScopes("App", "Child")

childScope.installModules(module {
   bind(...) // here is I bind some isolated(internal) instances that I need only in "Child" scope
   bind(IFace::class.java).to(Face::class.java).singleton() // also I bind some Interface to provide outside (like dagger's component)
})

// I want to provide some interface from my child scope to parent scope
parentScope.installModules(module {
    bind(IFace::class.java).toProviderInstance { childScope.getInstance(IFace::class.java) }.providesSingleton()
})

this code throws

Class xxx.xxx.IFace creates a cycle:

                              ===============================
                             ||                             ||
                             \/                             ||
   xxx.xxx.IFace  ||
                             ||                             ||
                              ===============================

this code is working, but it creates instance immediately

     bind(IFace::class.java).toInstance(childScope.getInstance(IFace::class.java)).singleton()

If I remove any cycles checking from toothpick, everything is working as I expected

the problem with this code from RuntimeCheckOnConfiguration.java

final LinkedHashSet<Pair> linkedHashSet = cycleDetectionStack.get();
if (linkedHashSet.contains(pair)) { // pair = IFace|null
  throw new CyclicDependencyException(Pair.getClassList(linkedHashSet), clazz);
}

we are trying to get IFace instance from child scope, but we already trying to get it from parent scope cycles checking code can’t understand it 😃

[morder]

parentScope.installModules(module {
    bind(IAdsManager::class.java).toProviderInstance { scope.getInstance(IAdsManager::class.java) }.providesSingleton()
})

Here is I want to bind an interface without creating of instance right now. Because it’s possible that IAdsManager will never instantiate because we don’t open some screen. For example, I open some screen (ViewModel), with injected IAdsManager, and then I call IAdsManager.init() to do network request. I want to do the job(create an instance of a manager) when it needed, for example when ViewModel is instantiated.

IAdsManager - it’s just for example. Overall I’m talking about an approach to solve this problem.

This code is solving the problem, but it creates the instance right in the app. I don’t like it.

parentScope.installModules(module {
    bind(IAdsManager::class.java).toProvider(scope.getInstance(IAdsManager::class.java)).singleton()
})

PS: To remind what I have tried to explain early, a top scope of a tree, cannot/must not depend from one of its child, because by design this top scope may have other children or no child at all, and it should be kept persistent.

I agree, and I think the toothpick is not designed to solve my problem clearly.

[morder]

fix https://github.com/stephanenicolas/toothpick/pull/428