Rework lists to each have their own getters

This was necessary for them to each have their own enumerable properties. The React Native ListViewDataSource uses Object.keys() to the indexes.

ReactNative/RealmRPC.mm

@@ -272,6 +272,7 @@ static JSGlobalContextRef s_context;
         return @{
              @"type": @(RJSTypeGet(realm::PropertyTypeArray).c_str()),
              @"id": @(oid),
+             @"size": @(array->link_view->size()),
              @"schema": [self objectSchemaToJSONObject:array->object_schema]
          };
     }

lib/lists.js

@@ -5,7 +5,7 @@ let util = require('./util');
 
 let idKey = Symbol();
 let realmKey = Symbol();
-let prototype = util.createListPrototype(getterForLength, getterForIndex, setterForIndex);
+let prototype = {};
 
 exports.create = create;
 
@@ -15,9 +15,7 @@ exports.create = create;
     'push',
     'unshift',
     'splice',
-].forEach(function(name, i) {
-    let growthMethod = (i >= 2);
-
+].forEach(function(name) {
     Object.defineProperty(prototype, name, {
         value: function() {
             let listId = this[idKey];
@@ -28,11 +26,7 @@ exports.create = create;
             }
 
             let result = rpc.callListMethod(realmId, listId, name, Array.from(arguments));
-
-            // Since this method might have grown the list, ensure index properties are defined.
-            if (growthMethod) {
-                prototype[util.growListPrototypeKey](this.length);
-            }
+            this[util.resizeListKey]();
 
             return result;
         }
@@ -40,13 +34,13 @@ exports.create = create;
 });
 
 function create(realmId, info) {
-    let list = Object.create(prototype);
+    let list = util.createList(prototype, getterForLength, getterForIndex, setterForIndex);
     let size = info.size;
 
     list[realmKey] = realmId;
     list[idKey] = info.id;
 
-    list[util.growListPrototypeKey](size);
+    list[util.resizeListKey](size);
 
     return list;
 }

lib/results.js

@@ -5,18 +5,17 @@ let util = require('./util');
 
 let idKey = Symbol();
 let realmKey = Symbol();
-let prototype = util.createListPrototype(getterForLength, getterForIndex);
 
 exports.create = create;
 
 function create(realmId, info) {
-    let results = Object.create(prototype);
+    let results = util.createList(null, getterForLength, getterForIndex);
     let size = info.size;
 
     results[realmKey] = realmId;
     results[idKey] = info.resultsId;
 
-    results[util.growListPrototypeKey](size);
+    results[util.resizeListKey](size);
 
     return results;
 }

lib/util.js

@@ -1,35 +1,45 @@
 'use strict';
 
-let growListPrototypeKey = exports.growListPrototypeKey = Symbol();
+let resizeListKey = exports.resizeListKey = Symbol();
 
-exports.createListPrototype = createListPrototype;
+exports.createList = createList;
 
-function createListPrototype(getterForLength, getterForIndex, setterForIndex) {
-    let prototype = {};
-    let maxSize = 0;
+function createList(prototype, getterForLength, getterForIndex, setterForIndex) {
+    var list = prototype ? Object.create(prototype) : {};
+    var size = 0;
 
-    Object.defineProperty(prototype, 'length', {
-        get: getterForLength
-    });
+    Object.defineProperty(list, 'length', {get: getterForLength});
 
-    prototype[growListPrototypeKey] = function(size) {
-        if (size < maxSize) {
+    list[resizeListKey] = function(length) {
+        if (length == null) {
+            length = this.length;
+        }
+        if (length == size) {
             return;
         }
 
+        if (length > size) {
             let props = {};
-        for (let i = maxSize; i <= size; i++) {
+
+            for (let i = size; i < length; i++) {
                 props[i] = {
                     get: getterForIndex(i),
                     set: setterForIndex && setterForIndex(i),
+                    enumerable: true,
+                    configurable: true,
                 };
             }
 
-        // TODO: Use ES6 Proxy once it's supported on Chrome!
-        Object.defineProperties(prototype, props);
-
-        maxSize = size + 1;
+            Object.defineProperties(this, props);
+        }
+        else if (length < size) {
+            for (let i = size - 1; i >= length; i--) {
+                delete this[i];
+            }
         }
 
-    return prototype;
+        size = length;
+    };
+
+    return list;
 }