Avoid side-effects when calling jQuery.hasData

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

src/data.js

@@ -21,11 +21,17 @@ function Data() {
 Data.uid = 1;
 
 Data.prototype = {
-	key: function( owner ) {
+	key: function( owner, options ) {
 		var descriptor = {},
 			// Check if the owner object already has a cache key
 			unlock = owner[ this.expando ];
 
+		// `readonly` calls from hasData, on owners with no key
+		// should not create new/empty cache records
+		if ( !unlock && (options && options.readonly) ) {
+			return null;
+		}
+
 		// If not, create one
 		if ( !unlock ) {
 			unlock = Data.uid++;
@@ -158,7 +164,7 @@ Data.prototype = {
 	},
 	hasData: function( owner ) {
 		return !jQuery.isEmptyObject(
-			this.cache[ this.key( owner ) ]
+			this.cache[ this.key( owner, { readonly: true }) ] || {}
 		);
 	},
 	discard: function( owner ) {

test/unit/data.js

@@ -51,6 +51,17 @@ test( "jQuery._data & _removeData, expected returns", function() {
 	);
 });
 
+test( "jQuery.hasData no side effects", function() {
+	expect(1);
+	var obj = {};
+
+	jQuery.hasData( obj );
+
+	equal( Object.getOwnPropertyNames( obj ).length, 0,
+		"No data expandos where added when calling jQuery.hasData(o)"
+	);
+});
+
 function dataTests (elem) {
 	var oldCacheLength, dataObj, internalDataObj, expected, actual;