Changing Eclipse Source folder output location generates duplicate classpathentries

[SchwingSK]

I want to change the output location to separate the test classes from my other classes.
I used the code provided in the Buildship 1.0.18 release notes (https://discuss.gradle.org/t/buildship-1-0-18-is-now-available/19012 ):

apply plugin: 'java'
apply plugin: 'eclipse'

eclipse {
    classpath {
        file {
            whenMerged {
                def src = entries.find { it.path == 'src/main/java' }
                src.output = "/$eclipse.project.name/classes/main-java"
            }
        }
    }
}

Note: I don't use Buildship; I only use the eclipse task to generate my eclipse project.

All works as expected, but when I run the eclipse task a second time, a duplicate (and invalid) classpathEntry is created, causing Eclipse to complain:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry path="bin" kind="output"/>
    <classpathentry output="/gradleSrcFolderOutput/classes/main-java" kind="src" path="src/main/java"/>
    <classpathentry kind="src" path="src/main/java"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
</classpath>

I tested this on Gradle 3.1 & 3.2.1 (on Windows 8.1, but can be reproduced on a Debian)
Here's the Build scan:
https://scans.gradle.com/s/agvrcrheznjyg

A workaround (provided by Stefan Oehme here ) is to lose the user-edited values:

beforeMerged {
  entries.clear()
}

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Given the limited bandwidth of the team, it will be automatically closed if no further activity occurs. If you're interested in how we try to keep the backlog in a healthy state, please read our blog post on how we refine our backlog. If you feel this is something you could contribute, please have a look at our Contributor Guide. Thank you for your contribution.

[stale]

This issue has been automatically closed due to inactivity. If you can reproduce this on a recent version of Gradle or if you have a good use case for this feature, please feel free to reopen the issue with steps to reproduce, a quick explanation of your use case or a high-quality pull request.