Understand hamcrest-core 2.x

[elharo]

Affected version

HEAD

Bug description

    <dependency>
      <groupId>org.hamcrest</groupId>
      <artifactId>hamcrest-core</artifactId>
      <version>2.2</version>
      <scope>test</scope>
    </dependency>

This one's an ugly mess. It has a purpose when present to avoid introducing a transitive dependency on hamcrest-core 1.3, which can happen with JUnit 4. However, it's just a shim that contains no classes and depends on hamcrest.

This creates one of the ugly unused when included and needed when not included warning Catch-22s.

In any case we should never report hamcrest-core 2.2 as unused. It contains nothing, causes no problems, and prevents other problems even though it contributes exactly zero classes to the classpath.

[elharo]

@slawekjaranowski notes that "Instead of using it you can exclude hamcrest-core from junit and then use hamcrest with the newer version". Might (or might not) be possible to note this in the warnings somehow

[slawekjaranowski]

hamcrest moved everything to one artifact, old artifacts are preserved for compatibility.

As you see old artifact contains only dependencies to new one, so should be ok

[elharo]

The problem is not hamcrest itself. It's that when you use it like this you get a warning that it's unused. Then you remove it and get a warning that it's declared but not used. You have to use the exclusion you suggested to prevent both warnings from appearing. The dependency plugin doesn't understand what's going on here.