commons-collections4 should be api dependency

[Vampire]

In your build script you define implementation("org.apache.commons:commons-collections4:4.1").
But commons-collections4 is used in your API (e. g. as return type of several methods in Message).
Due to that it should instead be declared as api("org.apache.commons:commons-collections4:4.1").

This is not only a philosophical change, this is how api and implementation are meant to be used.
And for me it also has a practical impact. (That I of course can work-around easily by including the lib on my compile classpath manually, but I shouldn't need to)

Due to it being defined as implementation dependency it lands as runtime-scoped dependency in the published POM and thus is not part of the compile classpath of Gradle 5+ consumers.

Now I have a project that is a consumer and have a Spock test that mocks a method call of Message.
This causes the test compilation to fail as the Spock Groovy AST transformation tries to get the methods of Message and fails with a NoClassDefFoundError as Bag is not on the compile classpath.

[MinnDevelopment]

You're right, I forgot to change it to api when I added the bag methods. PRs welcome.

[Andre601]

So just change a dependency to api?