Wrap Function.prototype.apply to accept Ruby arrays.

In the process, fix Array#length to be a JS property, too.

lib/johnson/js/prelude.js

@@ -27,6 +27,19 @@ Object.defineProperty(String.prototype, "toSymbol", function() {
   return Johnson.symbolize(this.toString());
 }, Object.READ_ONLY | Object.NON_DELETABLE);
 
+(function(origApply) {
+  Object.defineProperty(Function.prototype, "apply", function(thisObj, arrayLike) {
+    var realArray = arrayLike;
+    if (!(arrayLike instanceof Array)) {
+      realArray = [];
+      for (var i = arrayLike.length - 1; i >= 0; i--) {
+        realArray[i] = arrayLike[i];
+      }
+    }
+    return origApply.call(this, thisObj, realArray);
+  }, Object.READ_ONLY | Object.NON_DELETABLE);
+})(Function.prototype.apply);
+
 Johnson.Generator = function(enumerableProxy) {
   this.items = enumerableProxy.toArray();
   this.index = 0;

lib/johnson/spidermonkey/js_land_proxy.rb

@@ -1,3 +1,10 @@
+# FIXME: This definition should probably be somewhere else
+class Array
+  def js_property?(name)
+    name == :length
+  end
+end
+
 module Johnson
   module SpiderMonkey
     module JSLandProxy #:nodoc:

test/johnson/conversions/array_test.rb

@@ -14,6 +14,11 @@ def test_array_index_set
         assert_equal(42, @runtime[:list][0])
       end
 
+      def test_array_length
+        @runtime[:list] = [1, 2, 3, 4]
+        assert_equal(4, @runtime.evaluate("list.length"))
+      end
+
       def test_array_works_with_for_in
         list = [1, 2, 3, 4]
 
@@ -27,6 +32,24 @@ def test_array_works_with_for_in
         ")
         assert_equal(list.map { |x| x + 1}, @runtime['new_list'].to_a)
       end
+
+      def test_array_works_with_function_apply
+        list = [1, 2, 3, 4]
+
+        @runtime['alert'] = lambda { |x| p x }
+        @runtime['list'] = list
+        @runtime.evaluate("
+          var new_list = [];
+          function process_list(a, b, c, d) {
+            new_list.push(a * 2);
+            new_list.push(b * 2);
+            // skip c
+            new_list.push(d * 2);
+          }
+          process_list.apply(process_list, list);
+        ")
+        assert_equal([2, 4, 8], @runtime['new_list'].to_a)
+      end
     end
   end
 end