By default, Gradle does joint compilation only for Java and Groovy source under src/main/groovy. Anything in src/main/java is compiled on its own and cannot depend on Groovy classes.

This is arguably a pretty confusing default, and one which we should fix.

In the meantime, you can configure the groovy plugin to include src/main/java in joint compilation:

sourceSets.main.java.srcDirs = []
sourceSets.main.groovy.srcDir 'src/main/java'

Thanks for explanation and for your solution, it works nice.

@Adam: if you intend to change the current default behaviour, please include a clean and simple way to fall back to the current one.

I mean, we have projects with hundreds of Java classes and few Groovy classes, in which Java classes do not require Groovy classes. Making Gradle do joint compilation by default on src/main/java too would lead to a performance penalty in the build process in our case.

IMHO once one knows that joint compilation is done ONLY in src/main/groovy by default, moving his/her Java code to src/main/groovy or changing sourceSets definition in build.gradle when joint compilation is needed should not be a big trouble... So I personally absolutely prefer the current behaviour.

I have also hit this problem. Provided workaround works for me too.
Will be this issue fixed somehow or the current behaviour will stay unchanged?

The current behavior is how it was designed to work, and we don't currently have plans to change it. It's more likely that we'll revisit this topic once Groovy fundamentally changes its joint compilation approach (which is scheduled for Groovy 3.0).

@Adam: current design is the right approach for most projects. There is always the option to use src/main/groovy for all java + groovy code and is never going to be a problem.

Also the expected behaviour of having java and groovy compiled together in src/main/java is merely a configuration change as mentioned above. Anything more than that probably warrants its own sub project.

Also what of the compile*Scala tasks and any other future support for other languages. With polyglot programming becoming popular by the day in projects, any coupling of java and groovy should be made with considerations for other languages as well.

What in case of using packages from com.sun…. With recommended strategy of joint compilation(sourceSets.main.groovy.srcDir 'src/main/java') and using workaround for com.sun :
options.compilerArgs << '-XDignore.symbol.file=true'
options.fork = true
options.forkOptions.executable = 'javac'

doesn't work. I had to move dependency of com.sun into java files with different source root, which cannot depend on groovy files.
So I had to make it like that:
sourceSets.main.java.srcDirs = ['src/main/javaplain'] - here are only which depends on com.sun
sourceSets.main.groovy.srcDirs += ["src/main/java"] - rest
Thanks for any other ideas

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