Hide metadata when serializing JS objects using JSON.stringify via a toJSON hack. Fixes #8108.

src/data.js

@@ -24,7 +24,7 @@ jQuery.extend({
 	hasData: function( elem ) {
 		elem = elem.nodeType ? jQuery.cache[ elem[jQuery.expando] ] : elem[ jQuery.expando ];
 
-		return !!elem && !jQuery.isEmptyObject(elem);
+		return !!elem && !isEmptyDataObject( elem );
 	},
 
 	data: function( elem, name, data, pvt /* Internal Use Only */ ) {
@@ -64,6 +64,13 @@ jQuery.extend({
 
 		if ( !cache[ id ] ) {
 			cache[ id ] = {};
+
+			// TODO: This is a hack for 1.5 ONLY. Avoids exposing jQuery
+			// metadata on plain JS objects when the object is serialized using
+			// JSON.stringify
+			cache[ id ].toJSON = function () {
+				return undefined;
+			};
 		}
 
 		// An object can be passed to jQuery.data instead of a key/value pair; this gets
@@ -130,7 +137,7 @@ jQuery.extend({
 
 				// If there is no data left in the cache, we want to continue
 				// and let the cache object itself get destroyed
-				if ( !jQuery.isEmptyObject(thisCache) ) {
+				if ( !isEmptyDataObject(thisCache) ) {
 					return;
 				}
 			}
@@ -142,7 +149,7 @@ jQuery.extend({
 
 			// Don't destroy the parent cache unless the internal data object
 			// had been the only thing left in it
-			if ( !jQuery.isEmptyObject(cache[ id ]) ) {
+			if ( !isEmptyDataObject(cache[ id ]) ) {
 				return;
 			}
 		}
@@ -291,4 +298,17 @@ function dataAttr( elem, key, data ) {
 	return data;
 }
 
+// TODO: This is a hack for 1.5 ONLY to allow objects with a single toJSON
+// property to be considered empty objects; this property always exists in
+// order to make sure JSON.stringify does not expose internal metadata
+function isEmptyDataObject( obj ) {
+	for ( var name in obj ) {
+		if ( name !== "toJSON" ) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
 })( jQuery );

test/unit/data.js

@@ -180,7 +180,13 @@ test(".data()", function() {
 	var div = jQuery("#foo");
 	strictEqual( div.data("foo"), undefined, "Make sure that missing result is undefined" );
 	div.data("test", "success");
-	same( div.data(), {test: "success"}, "data() get the entire data object" );
+
+	var dataObj = div.data();
+
+	// TODO: Remove this hack which was introduced in 1.5.1
+	delete dataObj.toJSON;
+
+	same( dataObj, {test: "success"}, "data() get the entire data object" );
 	strictEqual( div.data("foo"), undefined, "Make sure that missing result is still undefined" );
 
 	var nodiv = jQuery("#unfound");
@@ -189,7 +195,10 @@ test(".data()", function() {
 	var obj = { foo: "bar" };
 	jQuery(obj).data("foo", "baz");
 
-	var dataObj = jQuery.extend(true, {}, jQuery(obj).data());
+	dataObj = jQuery.extend(true, {}, jQuery(obj).data());
+
+	// TODO: Remove this hack which was introduced for 1.5.1
+	delete dataObj.toJSON;
 
 	deepEqual( dataObj, { foo: "baz" }, "Retrieve data object from a wrapped JS object (#7524)" );
 });
@@ -329,12 +338,18 @@ test("data-* attributes", function() {
 		num++;
 	}
 
+	// TODO: Remove this hack which was introduced for 1.5.1
+	num--;
+
 	equals( num, check.length, "Make sure that the right number of properties came through." );
 
 	for ( var prop in obj2 ) {
 		num2++;
 	}
 
+	// TODO: Remove this hack which was introduced for 1.5.1
+	num2--;
+
 	equals( num2, check.length, "Make sure that the right number of properties came through." );
 
 	child.attr("data-other", "newvalue");
@@ -465,4 +480,15 @@ test(".removeData()", function() {
 
 	div.removeData("test.foo");
 	equals( div.data("test.foo"), undefined, "Make sure data is intact" );
-});
+});
\ No newline at end of file
+
+if (window.JSON && window.JSON.stringify) {
+	test("JSON serialization (#8108)", function () {
+		expect(1);
+
+		var obj = { foo: "bar" };
+		jQuery.data(obj, "hidden", true);
+
+		equals( JSON.stringify(obj), '{"foo":"bar"}', "Expando is hidden from JSON.stringify" );
+	});
+}
\ No newline at end of file