From eb6ba0d76dcb62c95f67bda08a643aa76ea6af8b Mon Sep 17 00:00:00 2001
From: Pavel Jbanov <pavelgj@gmail.com>
Date: Thu, 14 Nov 2013 16:42:30 -0800
Subject: [PATCH] fix(compiler): don't create watchers for attr mappings if no
 attr is specified

Closes #265
---
 lib/core_dom/compiler.dart       | 3 +++
 test/core_dom/compiler_spec.dart | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/lib/core_dom/compiler.dart b/lib/core_dom/compiler.dart
index f7f041163..c61c654f4 100644
--- a/lib/core_dom/compiler.dart
+++ b/lib/core_dom/compiler.dart
@@ -151,6 +151,7 @@ class Compiler {
           break;
         case '<=>':
           mappingFn = (NodeAttrs attrs, Scope scope, Object dst) {
+            if (attrs[attrName] == null) return;
             Expression attrExprFn = _parser(attrs[attrName]);
             var shadowValue = null;
             scope.$watch(
@@ -172,6 +173,7 @@ class Compiler {
           break;
         case '=>':
           mappingFn = (NodeAttrs attrs, Scope scope, Object dst) {
+            if (attrs[attrName] == null) return;
             Expression attrExprFn = _parser(attrs[attrName]);
             var shadowValue = null;
             scope.$watch(
@@ -182,6 +184,7 @@ class Compiler {
           break;
         case '=>!':
           mappingFn = (NodeAttrs attrs, Scope scope, Object dst) {
+            if (attrs[attrName] == null) return;
             Expression attrExprFn = _parser(attrs[attrName]);
             var stopWatching;
             stopWatching = scope.$watch(
diff --git a/test/core_dom/compiler_spec.dart b/test/core_dom/compiler_spec.dart
index 2845b042e..23d746488 100644
--- a/test/core_dom/compiler_spec.dart
+++ b/test/core_dom/compiler_spec.dart
@@ -244,6 +244,14 @@ main() => describe('dte.compiler', () {
         expect($rootScope.done).toEqual(true);
       })));
 
+      it('should should not create any watchers if no attributes are specified', async(inject((Profiler perf) {
+        var element = $(r'<div><io></io></div>');
+        $compile(element)(injector, element);
+        microLeap();
+        injector.get(Scope).$digest();
+        expect(perf.counters['ng.scope.watchers']).toEqual(0);
+      })));
+
       it('should create a component with I/O and "=" binding value should be available', async(inject(() {
         $rootScope.name = 'misko';
         var element = $(r'<div><io attr="A" expr="name" ondone="done=true"></io></div>');