fix(ng:class): make ng:class friendly towards other code adding/removing classes

ng:class as well as ng:class-odd and ng:class-even always reset the
class list to whatever it was before compilation, this makes it
impossible to create another directive which adds its own classes on the
element on which ng:class was applied.

the fix simply removes all classes that were added previously by
ng:class and add classes that the ng:class expression evaluates to.

we can now guarantee that we won't clobber stuff added before or after
compilation as long as all class names are unique.

in order to implement this I had to beef up jqLite#addClass and
jqLite#removeClass to be able to add/remove multiple classes without
creating duplicates.

2 files changed, 41 insertions, 26 deletions

diff --git a/src/directives.js b/src/directives.js
index b3584a37..2e1040c0 100644
--- a/src/directives.js
+++ b/src/directives.js
@@ -549,16 +549,11 @@ angularDirective("ng:submit", function(expression, element) {
 
 function ngClass(selector) {
   return function(expression, element) {
-    var existing = element[0].className + ' ';
     return function(element) {
-      this.$watch(function(scope) {
+      this.$watch(expression, function(scope, newVal, oldVal) {
         if (selector(scope.$index)) {
-          var ngClassVal = scope.$eval(element.attr('ng:class'));
-          if (isArray(ngClassVal)) ngClassVal = ngClassVal.join(' ');
-          var value = scope.$eval(expression);
-          if (isArray(value)) value = value.join(' ');
-          if (ngClassVal && ngClassVal !== value) value = value + ' ' + ngClassVal;
-          element[0].className = trim(existing + value);
+          element.removeClass(isArray(oldVal) ? oldVal.join(' ') : oldVal)
+          element.addClass(isArray(newVal) ? newVal.join(' ') : newVal);
         }
       });
     };
@@ -571,11 +566,17 @@ function ngClass(selector) {
  * @name angular.directive.ng:class
  *
  * @description
- * The `ng:class` allows you to set CSS class on HTML element
- * conditionally.
+ * The `ng:class` allows you to set CSS class on HTML element dynamically by databinding an
+ * expression that represents all classes to be added.
+ *
+ * The directive won't add duplicate classes if a particular class was already set.
+ *
+ * When the expression changes, the previously added classes are removed and only then the classes
+ * new classes are added.
  *
  * @element ANY
- * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval.
+ * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval. The result
+ *   of the evaluation can be a string representing space delimited class names or an array.
  *
  * @example
    <doc:example>
@@ -612,12 +613,15 @@ angularDirective("ng:class", ngClass(function(){return true;}));
  *
  * @description
  * The `ng:class-odd` and `ng:class-even` works exactly as
- * `ng:class`, except it works in conjunction with `ng:repeat`
- * and takes affect only on odd (even) rows.
+ * {@link angular.directive.ng:class ng:class}, except it works in conjunction with `ng:repeat` and
+ * takes affect only on odd (even) rows.
+ *
+ * This directive can be applied only within a scope of an
+ * {@link angular.widget.@ng:repeat ng:repeat}.
  *
  * @element ANY
- * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval. Must be
- *  inside `ng:repeat`.
+ * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval. The result
+ *   of the evaluation can be a string representing space delimited class names or an array.
  *
  * @example
    <doc:example>
@@ -650,12 +654,15 @@ angularDirective("ng:class-odd", ngClass(function(i){return i % 2 === 0;}));
  *
  * @description
  * The `ng:class-odd` and `ng:class-even` works exactly as
- * `ng:class`, except it works in conjunction with `ng:repeat`
- * and takes affect only on odd (even) rows.
+ * {@link angular.directive.ng:class ng:class}, except it works in conjunction with `ng:repeat` and
+ * takes affect only on odd (even) rows.
+ *
+ * This directive can be applied only within a scope of an
+ * {@link angular.widget.@ng:repeat ng:repeat}.
  *
  * @element ANY
- * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval. Must be
- *  inside `ng:repeat`.
+ * @param {expression} expression {@link guide/dev_guide.expressions Expression} to eval. The result
+ *   of the evaluation can be a string representing space delimited class names or an array.
  *
  * @example
    <doc:example>
diff --git a/src/jqLite.js b/src/jqLite.js
index 8cef64da..122684a5 100644
--- a/src/jqLite.js
+++ b/src/jqLite.js
@@ -155,16 +155,24 @@ function JQLiteHasClass(element, selector, _) {
 }
 
 function JQLiteRemoveClass(element, selector) {
-  element.className = trim(
-      (" " + element.className + " ")
-      .replace(/[\n\t]/g, " ")
-      .replace(" " + selector + " ", " ")
-  );
+  if (selector) {
+    forEach(selector.split(' '), function(cssClass) {
+      element.className = trim(
+          (" " + element.className + " ")
+          .replace(/[\n\t]/g, " ")
+          .replace(" " + trim(cssClass) + " ", " ")
+      );
+    });
+  }
 }
 
 function JQLiteAddClass(element, selector) {
-  if (selector && !JQLiteHasClass(element, selector)) {
-    element.className = trim(element.className + ' ' + selector);
+  if (selector) {
+    forEach(selector.split(' '), function(cssClass) {
+      if (!JQLiteHasClass(element, cssClass)) {
+        element.className = trim(element.className + ' ' + trim(cssClass));
+      }
+    });
   }
 }