Unwrap polyglot.Value?

[melvinm1]

Hello

We want to replace Nashorn with Graal in our application. In one part of our application, we use objects that are returned from JavaScript as keys in a Java WeakHashMap. This was possible in Nashorn, provided that the ScriptObjectMirror objects returned by Nashorn were first "unwrapped" using the ScriptObjectMirror.unwrap method. I haven't been able to accomplish the same thing using Graal. I tried to use polyglot.Value as keys in the WeakHashMap, but that doesn't seem to work as demonstrated by this example:

import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.Value;
import java.util.WeakHashMap;

public class Main {
    public static void main(String[] args) {
        WeakHashMap<Object, String> weakMap = new WeakHashMap<>();

        try (Context context = Context.create()) {
            // Define global object "obj" and return a getter function.
            Value getObj = context.eval("js", "let obj = { test: 123 }; (function getObj() { return obj; })");
            
            // Use the object as a key in the WeakMap.
            weakMap.put(getObj.execute(), "test");

            // Check if the key exists in the WeakMap.
            // Prints true.
            System.out.println(weakMap.containsKey(getObj.execute()));

            // Trigger garbage collection.
            System.gc();

            // Check again if the key exists in the WeakMap.
            // Should also print true, but prints false.
            System.out.println(weakMap.containsKey(getObj.execute()));
        }
    }
}

Each call to getObj.execute() seems to be returning different polyglot.Value instances. Is there a way to "unwrap" polyglot.Value, similar to Nashorn's ScriptObjectMirror.unwrap, so that objects returned from JavaScript could be used as keys in a WeakHashMap in Java? Or are there any other ways in which this could be accomplished?

[iamstolis]

I am not aware of a way to "unwrap" Value so that it would be usable with WeakHashMap but I guess that you can use JavaScript WeakMap instead of Java WeakHashMap.