John Keeping noted this issue and posted to nashorn-dev alias:

File: MyInterface.java

public interface MyInterface {
    void test(int i, String... strings);
}


File: Main.java

import javax.script.*;
import java.io.*;

public class Main {
   public static void main(String[] args) throws Exception {
       ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
       engine.eval(new FileReader(args[0]));
       Invocable inv = (Invocable) engine;
       MyInterface obj = inv.getInterface(MyInterface.class);
       obj.test(42, "hello", "world");
   }
}

File: file.js

function test(i, strings) {
    print('i = ' + i);
    print('strings = ' + strings);
}


File: file2.js

function test(i, strings) {
    for (var index = 0; index < arguments.length; index++)
        print('arg ' + index + ' = ' + arguments[index]);
}

When running the following commands:

    javac Main.java
    java Main file.js

we get the following output:

    i = 42
   strings = hello

We don't get strings to be an array and no way for script to access "world" argument passed.

When we run this command:

    java Main file2.js

(file2.js uses arguments in script function), we get the following error:

Exception in thread "main" java.lang.invoke.WrongMethodTypeException: Parameter counts differ: (Object[])Object vs. (int,String[])void
at jdk.internal.dynalink.support.TypeConverterFactory.asType(TypeConverterFactory.java:184)
at jdk.internal.dynalink.support.LinkerServicesImpl.asType(LinkerServicesImpl.java:123)
at jdk.nashorn.internal.runtime.linker.JavaAdapterFactory.adaptHandle(JavaAdapterFactory.java:751)
at jdk.nashorn.internal.runtime.linker.JavaAdapterFactory.getHandle(JavaAdapterFactory.java:742)
at jdk.nashorn.internal.javaadapters.MyInterface.<init>(Unknown Source)
at jdk.nashorn.api.scripting.NashornScriptEngine.getInterfaceInner(NashornScriptEngine.java:202)
at jdk.nashorn.api.scripting.NashornScriptEngine.getInterface(NashornScriptEngine.java:217)
at Main.main(Main.java:9)