fix(jqLite): never add to the cache for non-element/document nodes

Calling `jqLite.data()` on a disallowed node type caused an empty object to be added to the
cache. This could lead to memory leaks since we no longer clean up such node types when they are
removed from the DOM.

Closes #7966

src/jqLite.js

@@ -314,30 +314,29 @@ function jqLiteExpandoStore(element, key, value) {
 }
 
 function jqLiteData(element, key, value) {
-  var data = jqLiteExpandoStore(element, 'data'),
-      isSetter = isDefined(value),
-      keyDefined = !isSetter && isDefined(key),
-      isSimpleGetter = keyDefined && !isObject(key);
+  if (jqLiteAcceptsData(element)) {
+    var data = jqLiteExpandoStore(element, 'data'),
+        isSetter = isDefined(value),
+        keyDefined = !isSetter && isDefined(key),
+        isSimpleGetter = keyDefined && !isObject(key);
 
-  if (!data && !isSimpleGetter) {
-    jqLiteExpandoStore(element, 'data', data = {});
-  }
+    if (!data && !isSimpleGetter) {
+      jqLiteExpandoStore(element, 'data', data = {});
+    }
 
-  if (isSetter) {
-    // set data only on Elements and Documents
-    if (jqLiteAcceptsData(element)) {
+    if (isSetter) {
       data[key] = value;
-    }
-  } else {
-    if (keyDefined) {
-      if (isSimpleGetter) {
-        // don't create data in this case.
-        return data && data[key];
+    } else {
+      if (keyDefined) {
+        if (isSimpleGetter) {
+          // don't create data in this case.
+          return data && data[key];
+        } else {
+          extend(data, key);
+        }
       } else {
-        extend(data, key);
+        return data;
       }
-    } else {
-      return data;
     }
   }
 }

test/jqLiteSpec.js

@@ -386,6 +386,23 @@ describe('jqLite', function() {
       selected.removeData('prop2');
     });
 
+
+    it('should not add to the cache if the node is a comment or text node', function() {
+      var calcCacheSize = function() {
+        var count = 0;
+        for (var k in jqLite.cache) { ++count; }
+        return count;
+      };
+
+      var nodes = jqLite('<!-- some comment --> and some text');
+      expect(calcCacheSize()).toEqual(0);
+      nodes.data('someKey');
+      expect(calcCacheSize()).toEqual(0);
+      nodes.data('someKey', 'someValue');
+      expect(calcCacheSize()).toEqual(0);
+    });
+
+
     it('should emit $destroy event if element removed via remove()', function() {
       var log = '';
       var element = jqLite(a);