Support property observers which are direct function references in ad…

…dition to strings.

Provides better static analysis and refactoring support in multiple tools. Alleviates the need for property reflection with Closure-compiler renaming.

lib/mixins/property-effects.html

@@ -185,12 +185,12 @@
    * @private
    */
   function runObserverEffect(inst, property, props, oldProps, info) {
-    let fn = inst[info.methodName];
+    let fn = typeof info.method === 'function' ? info.method : inst[info.method];
     let changedProp = info.property;
     if (fn) {
       fn.call(inst, inst.__data[changedProp], oldProps[changedProp]);
     } else {
-      console.warn('observer method `' + info.methodName + '` not defined');
+      console.warn('observer method `' + info.method + '` not defined');
     }
   }
 
@@ -1899,19 +1899,19 @@
        * Creates a single-property observer for the given property.
        *
        * @param {string} property Property name
-       * @param {string} methodName Name of observer method to call
+       * @param {string|function(*,*)} method Name or function reference of observer method to call
        * @param {boolean=} dynamicFn Whether the method name should be included as
        *   a dependency to the effect.
        * @protected
        */
-      _createPropertyObserver(property, methodName, dynamicFn) {
-        let info = { property, methodName };
+      _createPropertyObserver(property, method, dynamicFn) {
+        let info = { property, method };
         this._addPropertyEffect(property, TYPES.OBSERVE, {
           fn: runObserverEffect, info, trigger: {name: property}
         });
         if (dynamicFn) {
-          this._addPropertyEffect(methodName, TYPES.OBSERVE, {
-            fn: runObserverEffect, info, trigger: {name: methodName}
+          this._addPropertyEffect(method, TYPES.OBSERVE, {
+            fn: runObserverEffect, info, trigger: {name: method}
           });
         }
       }

test/unit/property-effects-elements.html

@@ -433,6 +433,7 @@
 </script>
 
 <script>
+  var prop2Changed = sinon.spy();
   Polymer({
     is: 'x-prop',
     properties: {
@@ -442,12 +443,13 @@
       },
       prop2: {
         value: 'default',
-        observer: 'prop2Changed'
+        observer: prop2Changed
       }
     },
     created: function() {
       this.prop1Changed = sinon.spy();
-      this.prop2Changed = sinon.spy();
+      this.prop2Changed = prop2Changed;
+      prop2Changed.reset();
     }
   });
 </script>