fix(compiler): Merging of interpolated class attribute from directive template with replace:true works

Closes angular#1006

Author: maxmart

src/ng/compile.js

@@ -990,7 +990,7 @@ function $CompileProvider($provide) {
       directives.push({
         priority: 100,
         compile: valueFn(function(scope, element, attr) {
-          if (name === 'class') {
+          if (name === 'class' && attr[name]) {
             // we need to interpolate classes again, in the case the element was replaced
             // and therefore the two class attrs got merged - we want to interpolate the result
             interpolateFn = $interpolate(attr[name], true);

test/ng/compileSpec.js

@@ -1,3 +1,4 @@
+
 'use strict';
 
 describe('$compile', function() {
@@ -378,6 +379,15 @@ describe('$compile', function() {
               expect(element).toBe(attr.$$element);
             }
           }));
+          $compileProvider.directive('replaceWithInterpolatedClass', valueFn({
+            restrict: 'CAM',
+            replace: true,
+            template: '<div class="class_{{1+1}}">Replace with interpolated class!</div>',
+            compile: function(element, attr) {
+              attr.$set('compiled', 'COMPILED');
+              expect(element).toBe(attr.$$element);
+	    }
+          }));
         }));
 
 
@@ -456,6 +466,13 @@ describe('$compile', function() {
         }));
 
 
+        it('should handle interpolated css from replacing directive', inject(function($compile, $rootScope) {
+          element = $compile('<div replace-with-interpolated-class></div>')($rootScope);
+          $rootScope.$digest();
+          expect(element).toHaveClass('class_2');
+        }));
+
+
         it('should merge interpolated css class', inject(function($compile, $rootScope) {
           element = $compile('<div class="one {{cls}} three" replace></div>')($rootScope);