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March 18, 2016

Gradle Goodness: Source Sets As IntelliJ IDEA Modules

IntelliJ IDEA 2016.1 introduced better support for Gradle source sets. Each source set in our project becomes a module in the IntelliJ IDEA project. And each module has it's own dependencies, also between source sets. For example if we simply apply the java plugin in our project we already get two source sets: main and test. For compiling the test sources there is a dependency to the main source set. IntelliJ now knows how to handle this.

Let's create a sample Gradle build file with an extra custom source set and see what we get in IntelliJ IDEA. In the following example build file we add the source set api. This source set contains interfaces without implementations. The implementations for the interfaces are in the default main source set. Finally we have some tests in the test source set that depend on the classes generated by the api and main source sets.

apply plugin: 'groovy'
apply plugin: 'idea'

sourceSets {
    // Define new source set
    // with the name api. This 
    // source set contains interfaces,
    // implementation classes are in
    // the main source set.
    api
}

repositories {
    jcenter()
}

dependencies {

    // The default source set main
    // has a compile dependency on the 
    // output of the api source set.
    // Gradle will invoke the apiClasses
    // task automatically if we compile
    // the sources in the main source set.
    compile sourceSets.api.output
    
    testCompile 'org.spockframework:spock-core:1.0-groovy-2.4'
}

When we invoke the idea task to generate the IntelliJ IDEA project files or we import the build.gradle file into IDEA we can see in the Gradle tool window a new element: Source Sets. When we open the node we see all the source sets in our project with their dependencies:

When we right click on the project and select Open Module Settings we get a new dialog window. All source sets are separate modules grouped into a single module. In our example the module group is idea-sourcesets and it has three modules. If we click on the idea-sourcesets_test and select the Dependencies tab we see a list of dependencies for the source set:

Written with Gradle 2.12 and IntelliJ IDEA 2016.1.