Host Access with method scoping and VarArgs results in ArrayIndexOutOfBoundsException

[ferozco]

Hey folks,

After reading the Graal 22 announcement I was excited to pick up the new methodScoping feature, unfortunately when I did some of my tests started to fail with ArrayIndexOutOfBoundsException. It seems to be an issue with how "parameters" are counted with varArgs being grouped together into a single argument but treated as separate parameters when being added to the scope.

I've put together a minimal repro to demonstrate the broken behaviour and hopefully help you guys fix it.

public class ScopeAccessRepro {

    @Test
    void scopedHostAccess() {
        Context ctx = createContext(HostAccess.SCOPED);
        Value function = ctx.eval("js", "(host => host.scopedVarArgs(" + "\"hello\"," + "{}," + "{} " + "))");

        assertThatThrownBy(() -> function.execute(new HostClass()).as(Void.class))
                .isInstanceOf(PolyglotException.class)
                .hasMessageContaining("java.lang.ArrayIndexOutOfBoundsException");
    }

    @Test
    void nonScopedHostAccess() {
        Context ctx = createContext(
                HostAccess.newBuilder(HostAccess.SCOPED).methodScoping(false).build());

        Value function = ctx.eval("js", "(host => host.scopedVarArgs(" + "\"hello\"," + "{}," + "{} " + "))");

        function.execute(new HostClass()).as(Void.class);
    }

    private static Context createContext(HostAccess hostAccess) {
        return Context.newBuilder()
                .engine(Engine.newBuilder().build())
                .allowHostAccess(hostAccess)
                .build();
    }

    public final class HostClass {
        HostClass() {}

        @Export
        public void scopedVarArgs(String value1, Value... varArgs) {}
    }
}