[GROOVY-6357] Inner classes in Groovy should have the same access modifiers as in Java

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1.7
• Fix Version/s: 2.1.8
• Component/s: bytecode, class generator
• Assignee: Cédric Champeau
• Reporter: Rene Scheibe
• Created: 20/Sep/13 04:29
• Updated: 14/Oct/13 16:53
• Resolved: 14/Oct/13 03:38

Description

There are differences in the flags/access modifiers for inner classes between Java and Groovy.

Java code:

public class Java {
              class InnerPackage { }
    public    class InnerPublic { }
    protected class InnerProtected { }
    private   class InnerPrivate { }
}

Groovy code:

import groovy.transform.PackageScope

class Groovy {
    @PackageScope class InnerPackage { }
    public        class InnerPublic { }
    protected     class InnerProtected { }
    private       class InnerPrivate { }
}

Flags for inner classes (extracted via javap):

	package scope	public scope	protected scope	private scope
Java	ACC_SUPER	ACC_SUPER, ACC_PUBLIC	ACC_SUPER, ACC_PUBLIC	ACC_SUPER
Groovy	ACC_SUPER	ACC_SUPER, ACC_PUBLIC	ACC_SUPER, 0x4 (means ACC_PROTECTED)	ACC_SUPER, 0x2 (means ACC_PRIVATE)

Comment from blackdrag:

I think as Groovy does is correct. But we did learn only recently, that
the VMs have trouble doing it like this. AS a result we forbid the
private modifer on classes... but looks like we forgot inner classes.

These different flags for example result in Cobertura failing to instrument the inner classes because ASM throws this exception:

Unable to instrument file build/instrumented_classes/Groovy$InnerPrivate.class
java.lang.IllegalArgumentException: Invalid access flags: 34
        at org.objectweb.asm.util.CheckClassAdapter.checkAccess(Unknown Source)
        at org.objectweb.asm.util.CheckClassAdapter.visit(Unknown Source)
        at org.objectweb.asm.ClassVisitor.visit(Unknown Source)
        at net.sourceforge.cobertura.instrument.pass1.DetectDuplicatedCodeClassVisitor.visit(DetectDuplicatedCodeClassVisitor.java:205)
        at org.objectweb.asm.ClassReader.accept(Unknown Source)
        at org.objectweb.asm.ClassReader.accept(Unknown Source)
        at net.sourceforge.cobertura.instrument.CoberturaInstrumenter.instrumentClass(CoberturaInstrumenter.java:153)
        at net.sourceforge.cobertura.instrument.CoberturaInstrumenter.instrumentClass(CoberturaInstrumenter.java:121)
        at net.sourceforge.cobertura.instrument.CoberturaInstrumenter.addInstrumentationToSingleClass(CoberturaInstrumenter.java:234)
        at net.sourceforge.cobertura.instrument.Main.addInstrumentationToSingleClass(Main.java:298)
        at net.sourceforge.cobertura.instrument.Main.addInstrumentation(Main.java:307)
        at net.sourceforge.cobertura.instrument.Main.addInstrumentation(Main.java:316)
        at net.sourceforge.cobertura.instrument.Main.parseArguments(Main.java:399)
        at net.sourceforge.cobertura.instrument.Main.main(Main.java:421)
        at net.saliman.gradle.plugin.cobertura.CoberturaRunner.instrument(CoberturaRunner.java:79)