Shadow Version

6.1.0

Gradle Version

6.3

Expected Behavior

A project with application and shadow plugins applied.
The project makes use of Java modules, thus mainClassName is set to

ext.moduleName = 'org.kordamp.ikonli.browser'
ext.moduleMainClass = 'org.kordamp.ikonli.browser.Launcher'

mainClassName = "${moduleName}/${moduleMainClass}"

The shaded JAR should not be a modular JAR thus its entry point should only be moduleMainClass.

shadowJar {
    manifest {
        attributes('Main-Class': moduleMainClass)
    }
}

Should result in the manifest containing an entry as the following one

Main-Class: org.kordamp.ikonli.browser.Launcher

Actual Behavior

The generated manifest contains the full modularized main class

Main-Class: org.kordamp.ikonli.browser/org.kordamp.ikonli.browser.Launch
  er

Even if the following is added

shadowJar.doLast {
    manifest.attributes('Main-Class': moduleMainClass)
}

It seems https://github.com/johnrengelman/shadow/blob/master/src/main/groovy/com/github/jengelman/gradle/plugins/shadow/ShadowApplicationPlugin.groovy#L59-L64 always takes effect no matter what.