Duplicate source path entries in classpath

[hacki11]

hi!

i'm experiencing an issue having build config with eclipse plugin activated.
Sourcefolder src/main/java and src/main/test will be duplicate in generated .classpath file. this results in a BuildPathError within eclipse.

.classpath without BuildConfig plugin activated after build task:

<classpath>
    <classpathentry path="bin" kind="output"/>
    <classpathentry kind="src" path="src/main/java"/>
    <classpathentry kind="src" path="src/test/java"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
</classpath>

.classpath with BuildConfig activated after build task:

<classpath>
	<classpathentry kind="src" path="src/main/java"/>
	<classpathentry kind="src" path="src/test/java"/>
	<classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
	<classpathentry kind="output" path="bin/default"/>
	<classpathentry output="bin/main" kind="src" path="src/main/java">
		<attributes>
			<attribute name="gradle_scope" value="main"/>
			<attribute name="gradle_used_by_scope" value="main,test"/>
		</attributes>
	</classpathentry>
	<classpathentry output="bin/test" kind="src" path="src/test/java">
		<attributes>
			<attribute name="gradle_scope" value="test"/>
			<attribute name="gradle_used_by_scope" value="test"/>
		</attributes>
	</classpathentry>
	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
</classpath>

Eclipse is angry having two build path entries (src/main/java and test).

my workaround is eliminating the duplicate entries:

// this eliminates duplicate entries in .classpath
eclipse {
    classpath {
        file.whenMerged { cp ->
            logger.lifecycle "Removing duplicate classpath entries from eclipse for project '${project.name}'"

            Map entryByPath = cp.entries.groupBy { entry -> entry.path }
            entryByPath.each { key, values ->
                if (values.size() > 1) {
                    def entry = values.first()
                    if (entry.kind == 'src') {
                        entry.includes = []
                        entry.excludes = []
                    }
                    int index = cp.entries.indexOf entry
                    logger.lifecycle "Removing ${values.collect { it.path }}"
                    cp.entries.removeAll values
                    logger.lifecycle "Adding ${entry.path}"
                    cp.entries.add index, entry
                }
            }
        }
    }
}

BuildConfigPlugin 1.1.8
Gradle 4.8