Use List as vararg item in Jenkins pipeline (spread operator is disabled) #groovy #jenkins

useListAsVarargItem.groovy

def foo(Object... args) { 
    def normalizedArgs = []
    if (args != null) {
        if (args.size() == 1) {
            normalizedArgs << args[0]
        } else {
            normalizedArgs += args.toList()
        }
    }
    print('foo(varargs): ' + normalizedArgs.size() + ': ')
    println normalizedArgs.join(', ')
}

def foo(List args) {
    print 'foo(List): '
    foo(args as Object[])
}


foo 1                   //  foo(varargs): 1: 1
foo([[1]])              //  foo(List): foo(varargs): 1: [1]
foo 1, 2, 3             //  foo(varargs): 3: 1, 2, 3
foo()                   //  foo(varargs): 0:
foo null                //  foo(List): foo(varargs): 0:
foo null, null          //  foo(varargs): 2: null, null
foo([null])             //  foo(List): foo(varargs): 1: null
foo([1, 2, 3])          //  foo(List): foo(varargs): 3: 1, 2, 3
foo([1, 2, 3], 2)       //  foo(varargs): 2: [1, 2, 3], 2
foo(*[1, 2, 3])         //  foo(varargs): 3: 1, 2, 3              (not allowed in Jenkins pipeline)
foo(*[1, 2, 3], 4)      //  foo(varargs): 4: 1, 2, 3, 4           (not allowed in Jenkins pipeline)