Processor error on missing type while traversing too far up component dependency chain.

Module ‘test-a’:

public final class A {
  @Inject A() {}
}

@Component
public interface ComponentA {
  A a();
}

Module ‘test-b’ which has implementation project(':test-a'):

public final class B {
  @Inject B(A a) {}
}

@Component(dependencies = ComponentA.class)
public interface ComponentB {
  B b();
}

Module ‘test-c’ which has implementation project(':test-b'):

public final class C {
  @Inject C(B b) {}
}

@Component(dependencies = ComponentB.class)
public interface ComponentC {
  C c();
}

fails with:

> Task :test-c:compileDebugJavaWithJavac FAILED
error: cannot access ComponentA
  class file for test.a.ComponentA not found
  Consult the following stack trace for details.
  com.sun.tools.javac.code.Symbol$CompletionFailure: class file for test.a.ComponentA not found
1 error

which makes sense, because ‘test-c’ isn’t meant to see ‘test-a’ as it’s an implementation detail of ‘test-b’, but why is Dagger in ‘test-c’ trying to do anything with ComponentA? Once it reaches ComponentB and sees the required B type exposed shouldn’t it stop?

[ronshapiro]

We fully understand the issue you’re seeing, that’s not the problem.

I think the best recommendation I have now is not to use implementation with dagger components in your component dependencies chain.

[vRallev]

I’d like to bring this issue up again. I understand why it happens and why it isn’t purely Dagger’s fault. But the build tools (Gradle in this case) and Dagger don’t work well together. There are only two solutions at the moment for Gradle: Add the dependencies with api to the library module and fully expose them (not great for modularization) or add missing dependencies as compileOnly (or maybe even annotationProcessor / kapt) to the modules that need them, what isn’t good for modularization and isolation either.

I don’t have any hands-on experience with Blaze or Bazel, but I heard it can solve this issue with its finer granularity. But for many people those tools aren’t feasible.

How could Dagger avoid this issue? By turning off the cyclic dependency check?