gradle-api-source.gradle

import org.gradle.plugins.ide.eclipse.model.AbstractLibrary
import org.gradle.plugins.ide.eclipse.model.internal.FileReferenceFactory

eclipse {
    classpath {
        file {
            whenMerged { classpath ->
                def gradleHome = gradle.gradleHomeDir.absolutePath.replace(File.separator, '/')
                def gradleSrc = "${gradleHome}/src"
                classpath.entries.each { entry ->
                    if ((entry in AbstractLibrary) && (entry.library.file.name.
                            startsWith('gradle-'))) {
                        def matcher = entry.library.file.name =~ "gradle-(.*)-(.*)"
                        entry.sourcePath = new FileReferenceFactory().
                                fromPath(gradleSrc + '/' + matcher[0][1])
                    }
                }
            }
        }
    }
}