Dependencies with exceptions

[olenz]

ArchUnit is great and helps us a lot!

However, I have one problem. I feel that there should be a solution, only I haven't understood how to formulate the rule.

What I want to express is that no class from package "a" should depend on any class in "b", unless it is in "b.c".

noClasses()
    .that().resideInAnyPackage("a..")
    .should().dependOnClassesThat().resideInAnyPackage("b..")
            .butNot().resideInAnyPackage("b.c..");

The difficulty is the butNot(), which doesn't exist.

I have tried the inverse, which looks like this:

classes()
    .that().resideInAnyPackage("b..")
    .and().resideOutsideOfPackage("b.c..")
    .should().onlyHaveDependentClassesThat().resideOutsideOfPackages("a..");

...but that is a test of the classes in c, not of the classes in a. If the classes that I have loaded only contain the classes from a, then this won't help me. Or will it?

Of course, I could use the freeze functionality for this, but I would prefer to use freeze for real exceptions that I would like to get rid of, not for actual intentional cases.

[olenz]

I have managed to get it working with the following rule:

noClasses()
    .that().resideInAnyPackage("a..")
    .should().dependOnClassesThat().resideInAPackage("b..")
    .andShould(not(dependOnClassesThat(JavaClass.Predicates.resideInAnyPackage("b.c.."))))

It is clear that one could extend the Lang to cover this. However, the double negation noClasses() ... andShould(not(...)) feels clumsy to me. Any better suggestions?