I've made changes to Rhino such that its default behavior is now only to treat

Iterables or Iterators specially when they are arguments to the new Iterator
constructor:

js> m = new java.util.HashMap()
{}
js> m.put("a",1)
null
js> m.put("b",2)
null
js> m
{a=1.0, b=2.0}
js> for (i in m.values()) print(i)
notifyAll
removeAll
containsAll
contains
empty
equals
notify
class
isEmpty
add
size
iterator
clear
wait
retainAll
toString
hashCode
toArray
addAll
getClass
remove
js> for (i in Iterator(m.values())) print(i)
1.0
2.0
js> for (i in Iterator(m.values().iterator())) print(i)
1.0
2.0
js>

Since Iterator is a new addition for 1.7, there are no issues for backwards
compatibility.

This still leaves open the possibility of top-level functions to wrap Maps and
Lists as JavaScript Objects and Arrays.

js/rhino/src/org/mozilla/javascript/JavaMembers.java

@@ -640,20 +640,6 @@ class JavaMembers
             }
         }
 
-        // For objects that implement java.lang.Iterable, provide a
-        // __iterator__ property
-        if (iterableClass != null && iterableClass.isAssignableFrom(cl) &&
-            members.get(NativeIterator.ITERATOR_PROPERTY_NAME) == null &&
-            staticMembers.get(NativeIterator.ITERATOR_PROPERTY_NAME) == null)
-        {
-            Method m = VMBridge.instance.getIteratorMethod();
-            if (m != null) {
-                members.put(NativeIterator.ITERATOR_PROPERTY_NAME,
-                    new FunctionObject(NativeIterator.ITERATOR_PROPERTY_NAME,
-                    m, scope));
-            }
-        }
-
         // Reflect constructors
         Constructor[] constructors = getAccessibleConstructors();
         ctors = new MemberBox[constructors.length];
@@ -874,7 +860,6 @@ class JavaMembers
     private Hashtable staticFieldAndMethods;
     MemberBox[] ctors;
     private boolean includePrivate;
-    private static Class iterableClass = Kit.classOrNull("java.lang.Iterable");
 }
 
 class BeanProperty

js/rhino/src/org/mozilla/javascript/NativeIterator.java

@@ -30,6 +30,8 @@
 
 package org.mozilla.javascript;
 
+import java.util.Iterator;
+
 /**
  * This class implements iterator objects. See 
  * http://developer.mozilla.org/en/docs/New_in_JavaScript_1.7#Iterators
@@ -161,10 +163,24 @@ public final class NativeIterator extends IdScriptableObject {
         boolean keyOnly = args.length > 1 && ScriptRuntime.toBoolean(args[1]);
         if (thisObj != null) {
             // Called as a function. Convert to iterator if possible.
-            Scriptable iterator = ScriptRuntime.toIterator(cx, scope, obj, 
-                                                           keyOnly);
+          
+            // For objects that implement java.lang.Iterable or
+            // java.util.Iterator, have JavaScript Iterator call the underlying
+            // iteration methods
+            Iterator iterator = 
+                VMBridge.instance.getJavaIterator(cx, scope, obj);
             if (iterator != null) {
-                return iterator;
+                scope = ScriptableObject.getTopLevelScope(scope);
+                return cx.getWrapFactory().wrap(cx, scope,
+                        new WrappedJavaIterator(iterator, scope),
+                        WrappedJavaIterator.class);
+            }
+            
+            // Otherwise, just call the runtime routine
+            Scriptable jsIterator = ScriptRuntime.toIterator(cx, scope, obj, 
+                                                             keyOnly);
+            if (jsIterator != null) {
+                return jsIterator;
             }
         }
         
@@ -194,6 +210,30 @@ public final class NativeIterator extends IdScriptableObject {
         return cx.newArray(scope, elements);
     }
     
+    static public class WrappedJavaIterator
+    {
+        WrappedJavaIterator(Iterator iterator, Scriptable scope) {
+            this.iterator = iterator;
+            this.scope = scope;
+        }
+
+        public Object next() {
+            if (!iterator.hasNext()) {
+                // Out of values. Throw StopIteration.
+                throw new JavaScriptException(
+                    NativeIterator.getStopIterationObject(scope), null, 0);
+            }
+            return iterator.next();
+        }
+
+        public Object __iterator__(boolean b) {
+            return this;
+        }
+
+        private Iterator iterator;
+        private Scriptable scope;
+    }
+    
 // #string_id_map#
 
     protected int findPrototypeId(String s) {

js/rhino/src/org/mozilla/javascript/VMBridge.java

@@ -41,6 +41,7 @@ package org.mozilla.javascript;
 
 import java.lang.reflect.Method;
 import java.lang.reflect.Member;
+import java.util.Iterator;
 
 public abstract class VMBridge
 {
@@ -165,10 +166,18 @@ public abstract class VMBridge
     protected abstract boolean isVarArgs(Member member);
 
     /**
-     * return method corresponding to __iterator__ for treating a
-     * java.lang.Iterable as a JavaScript Iterator
+     * If "obj" is a java.util.Iterator or a java.lang.Iterable, return a
+     * wrapping as a JavaScript Iterator. Otherwise, return null.
+     * This method is in VMBridge since Iterable is a JDK 1.5 addition.
      */
-    public Method getIteratorMethod() {
+    public Iterator getJavaIterator(Context cx, Scriptable scope, Object obj) {
+        if (obj instanceof Wrapper) {
+            Object unwrapped = ((Wrapper) obj).unwrap();
+            Iterator iterator = null;
+            if (unwrapped instanceof Iterator)
+                iterator = (Iterator) unwrapped;
+            return iterator;
+        }
         return null;
     }
 }

js/rhino/src/org/mozilla/javascript/jdk15/VMBridge_jdk15.java

@@ -52,7 +52,7 @@ public class VMBridge_jdk15 extends org.mozilla.javascript.jdk13.VMBridge_jdk13
             // so that we can load a bridge to an older JDK instead.
             Method.class.getMethod("isVarArgs", (Class[]) null);
         } catch (NoSuchMethodException e) {
-            // Throw a fittitng exception that is handled by
+            // Throw a fitting exception that is handled by
             // org.mozilla.javascript.Kit.newInstanceOrNull:
             throw new InstantiationException(e.getMessage());
         }
@@ -67,55 +67,21 @@ public class VMBridge_jdk15 extends org.mozilla.javascript.jdk13.VMBridge_jdk13
             return false;
     }
     
-    public Method getIteratorMethod() {
-        try {
-            Class[] sig = { Context.class, Scriptable.class,
-                            ScriptRuntime.emptyArgs.getClass(),
-                            Function.class };
-            return VMBridge_jdk15.class.getMethod("__iterator__", sig);
-        } catch (NoSuchMethodException e) {
+    /**
+     * If "obj" is a java.util.Iterator or a java.lang.Iterable, return a
+     * wrapping as a JavaScript Iterator. Otherwise, return null.
+     * This method is in VMBridge since Iterable is a JDK 1.5 addition.
+     */
+    public Iterator getJavaIterator(Context cx, Scriptable scope, Object obj) {
+        if (obj instanceof Wrapper) {
+            Object unwrapped = ((Wrapper) obj).unwrap();
+            Iterator iterator = null;
+            if (unwrapped instanceof Iterator)
+                iterator = (Iterator) unwrapped;
+            if (unwrapped instanceof Iterable)
+                iterator = ((Iterable)unwrapped).iterator();
+            return iterator;
+        }
         return null;
     }
 }
-
-    public static Object __iterator__(Context cx, Scriptable thisObj,
-                                      Object[] args, Function funObj)
-    {
-        if (thisObj instanceof Wrapper) {
-            Object obj = ((Wrapper) thisObj).unwrap();
-            if (obj instanceof Iterable) {
-                Scriptable scope = ScriptableObject.getTopLevelScope(funObj);
-                return cx.getWrapFactory().wrap(cx, scope,
-                        new WrappedJavaIterator((Iterable) obj, scope),
-                        WrappedJavaIterator.class);
-            }
-        }
-        throw ScriptRuntime.typeError1("msg.incompat.call",
-                                       NativeIterator.ITERATOR_PROPERTY_NAME);
-    }
-
-    static public class WrappedJavaIterator
-    {
-        WrappedJavaIterator(Iterable iterable, Scriptable scope) {
-            this.iterator = iterable.iterator();
-            this.scope = scope;
-        }
-
-        public Object next() {
-            if (!iterator.hasNext()) {
-                // Out of values. Throw StopIteration.
-                throw new JavaScriptException(
-                    NativeIterator.getStopIterationObject(scope), null, 0);
-            }
-            return iterator.next();
-        }
-
-        public Object __iterator__() {
-            return this;
-        }
-
-        private Iterator iterator;
-        private Scriptable scope;
-    }
-
-}