Rewriting Vert.x JsonObject to make it JS-friendly in ES4X / GraalVM

RewriteJsonObject.java

import org.objectweb.asm.*;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Arrays;

import static org.objectweb.asm.ClassWriter.COMPUTE_FRAMES;
import static org.objectweb.asm.Opcodes.*;

public class RewriteJsonObject {

    public static void main(String[] args) throws Throwable {
        if (args.length != 2) {
            System.out.println("Give me 2 arguments: the path to the original class file and the path to the rewritten one");
            System.exit(1);
        } else {
            rewrite(new File(args[0]), new File(args[1]));
        }
    }

    static void rewrite(File source, File target) throws IOException {
        ClassReader classReader = new ClassReader(new FileInputStream(source));
        ClassWriter classWriter = new ClassWriter(COMPUTE_FRAMES) {
            @Override
            protected String getCommonSuperClass(String type1, String type2) {
                // Because we can't load dependent classes, this pleases the frame computation algorithm
                return "java/lang/Object";
            }
        };
        Enhancer enhancer = new Enhancer(ASM7, classWriter);

        classReader.accept(enhancer, 0);

        FileOutputStream out = new FileOutputStream(target);
        out.write(classWriter.toByteArray());
        out.close();
    }

    static class Enhancer extends ClassVisitor {

        public Enhancer(int api, ClassVisitor classVisitor) {
            super(api, classVisitor);
        }

        @Override
        public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
            String[] newInterfaces = new String[interfaces.length + 1];
            System.arraycopy(interfaces, 0, newInterfaces, 0, interfaces.length);
            newInterfaces[interfaces.length] = "org/graalvm/polyglot/proxy/ProxyObject";
            String newSignature = signature + "Lorg/graalvm/polyglot/proxy/ProxyObject;";
            System.out.println("sig  = " + signature);
            System.out.println("sig' = " + newSignature);
            System.out.println(Arrays.toString(interfaces));
            System.out.println(Arrays.toString(newInterfaces));
            super.visit(version, access, name, newSignature, superName, newInterfaces);
        }

        @Override
        public void visitEnd() {
            generateGetMember();
            generateGetMemberKeys();
            generateHasMember();
            generatePutMember();
            generateRemoveMember();
            super.visitEnd();
        }

        private void generateGetMember() {
            MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "getMember", "(Ljava/lang/String;)Ljava/lang/Object;", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitMethodInsn(INVOKEVIRTUAL, "io/vertx/core/json/JsonObject", "getValue", "(Ljava/lang/String;)Ljava/lang/Object;", false);
            mv.visitInsn(ARETURN);
            mv.visitMaxs(2, 2);
            mv.visitEnd();
        }

        private void generateGetMemberKeys() {
            MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "getMemberKeys", "()Ljava/lang/Object;", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKEVIRTUAL, "io/vertx/core/json/JsonObject", "fieldNames", "()Ljava/util/Set;", false);
            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/Set", "toArray", "()[Ljava/lang/Object;", true);
            mv.visitInsn(ARETURN);
            mv.visitMaxs(1, 1);
            mv.visitEnd();
        }

        private void generateHasMember() {
            MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "hasMember", "(Ljava/lang/String;)Z", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitMethodInsn(INVOKEVIRTUAL, "io/vertx/core/json/JsonObject", "containsKey", "(Ljava/lang/String;)Z", false);
            mv.visitInsn(IRETURN);
            mv.visitMaxs(2, 2);
            mv.visitEnd();
        }

        private void generatePutMember() {
            MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "putMember", "(Ljava/lang/String;Lorg/graalvm/polyglot/Value;)V", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitVarInsn(ALOAD, 2);
            mv.visitLdcInsn(Type.getType(Object.class));
            mv.visitMethodInsn(INVOKEVIRTUAL, "org/graalvm/polyglot/Value", "as", "(Ljava/lang/Class;)Ljava/lang/Object;", false);
            mv.visitMethodInsn(INVOKEVIRTUAL, "io/vertx/core/json/JsonObject", "put", "(Ljava/lang/String;Ljava/lang/Object;)Lio/vertx/core/json/JsonObject;", false);
            mv.visitInsn(POP);
            mv.visitInsn(RETURN);
            mv.visitMaxs(3, 3);
            mv.visitEnd();
        }

        private void generateRemoveMember() {
            MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "removeMember", "(Ljava/lang/String;)Z", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitMethodInsn(INVOKEVIRTUAL, "io/vertx/core/json/JsonObject", "remove", "(Ljava/lang/String;)Ljava/lang/Object;", false);
            Label falseLabel = new Label();
            mv.visitJumpInsn(IFNULL, falseLabel);
            mv.visitLdcInsn(true);
            mv.visitInsn(IRETURN);
            mv.visitLabel(falseLabel);
            mv.visitLdcInsn(false);
            mv.visitInsn(IRETURN);
            mv.visitMaxs(2, 2);
            mv.visitEnd();
        }
    }
}