[GROOVY-6567] delegate is NullObject instance for closure metamethods invoked on null

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.0-rc-1
• Fix Version/s: 5.0.0-alpha-3
• Assignee: Eric Milles
• Reporter: Lari Hotari
• Created: 10/Feb/14 09:51
• Updated: 22/Dec/23 11:38
• Resolved: 17/Oct/23 17:31

Description

NullObject shouldn't be exposed outside groovy internals.

This code example shows when NullObject leaks to application code:

Object.metaClass.delegateClass = { 
    delegate?.getClass()
}
println null.delegateClass().name

This prints out "org.codehaus.groovy.runtime.NullObject".

-------

possible solution:

I assume that NullObject should be "filtered" in ClosureMetaMethod.

    public Object invoke(final Object object, Object[] arguments) {
        Closure cloned = (Closure) callable.clone();
        cloned.setDelegate(object);

        arguments = coerceArgumentsToClasses(arguments);
        return doCall.invoke(cloned, arguments);
    }

replacing "cloned.setDelegate(object)" with

cloned.setDelegate(!(object instanceof NullObject) ? object : null)

would prevent the leak of NullObject in ClosureMetaMethod class.

Issue Links

• relates to: GROOVY-11196 ambiguous method error for tap on null receiver