Support for compileOnly dependencies

[snicoll]

The new devtools could use to have an <optional>true</optional> entry as it shouldn't ship with the actual app by default.

Provided scope is not managed properly in Intellij IDEA so that's not a great candidate unfortunately (and the semantic would be wrong anyway).

[dsyer]

I guess that means we have to have an answer to the question "what does 'optional' mean for a gradle dependency?". Refs: https://issues.gradle.org/browse/GRADLE-1749, https://github.com/nebula-plugins/gradle-extra-configurations-plugin.

[snicoll]

We already have a plugin of our own that does that and we use it in the Spring Framework build so all it takes really is integrating the plugin in the gradle build when an optional and/or provided dependency is added to the project

The only thing I don't know for sure is whether the Spring Boot repackage goal is smart enough to react to that.

[snicoll]

OK so I've started to work on this. We have 3 cases at this point:

• Lombok (annotation processor)
• The Spring Boot configuration processor (ditto)
• Devtools

We can deal with all these with "optional" in Maven. And ignore Gradle but the first two could be handled with the new compileOnly thing in Gradle. I am not sure that devtools will work (and even if it did, it's a bit weird).

@wilkinsona any insight?

[wilkinsona]

compileOnly is perfect for annotation processors. It won't work for DevTools as compileOnly dependencies aren't on the class path at runtime.