Landing pull request 500. 1.7 - "public data" stored as a key on "internal data" - Fixes #8921.

More Details:
 - https://github.com/jquery/jquery/pull/500
 - http://bugs.jquery.com/ticket/8921

src/data.js

@@ -24,7 +24,6 @@ jQuery.extend({
 
 	hasData: function( elem ) {
 		elem = elem.nodeType ? jQuery.cache[ elem[jQuery.expando] ] : elem[ jQuery.expando ];
-
 		return !!elem && !isEmptyDataObject( elem );
 	},
 
@@ -51,7 +50,7 @@ jQuery.extend({
 
 		// Avoid doing any more work than we need to when trying to get data on an
 		// object that has no data at all
-		if ( (!id || (pvt && id && (cache[ id ] && !cache[ id ][ internalKey ]))) && getByName && data === undefined ) {
+		if ( (!id || !cache[id] || (!pvt && !cache[id].data)) && getByName && data === undefined ) {
 			return;
 		}
 
@@ -68,9 +67,8 @@ 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
+			// Avoids exposing jQuery metadata on plain JS objects when the object 
+			// is serialized using JSON.stringify
 			if ( !isNode ) {
 				cache[ id ].toJSON = jQuery.noop;
 			}
@@ -80,23 +78,23 @@ jQuery.extend({
 		// shallow copied over onto the existing cache
 		if ( typeof name === "object" || typeof name === "function" ) {
 			if ( pvt ) {
-				cache[ id ][ internalKey ] = jQuery.extend(cache[ id ][ internalKey ], name);
+				cache[ id ] = jQuery.extend( cache[ id ], name );
 			} else {
-				cache[ id ] = jQuery.extend(cache[ id ], name);
+				cache[ id ].data = jQuery.extend( cache[ id ].data, name );
 			}
 		}
 
 		thisCache = cache[ id ];
 
-		// Internal jQuery data is stored in a separate object inside the object's data
+		// jQuery data() is stored in a separate object inside the object's internal data
 		// cache in order to avoid key collisions between internal data and user-defined
-		// data
-		if ( pvt ) {
-			if ( !thisCache[ internalKey ] ) {
-				thisCache[ internalKey ] = {};
+		// data.
+		if ( !pvt ) {
+			if ( !thisCache.data ) {
+				thisCache.data = {};
 			}
 
-			thisCache = thisCache[ internalKey ];
+			thisCache = thisCache.data;
 		}
 
 		if ( data !== undefined ) {
@@ -156,7 +154,7 @@ jQuery.extend({
 
 		if ( name ) {
 
-			thisCache = pvt ? cache[ id ][ internalKey ] : cache[ id ];
+			thisCache = pvt ? cache[ id ] : cache[ id ].data;
 
 			if ( thisCache ) {
 
@@ -169,15 +167,15 @@ jQuery.extend({
 
 				// If there is no data left in the cache, we want to continue
 				// and let the cache object itself get destroyed
-				if ( !isEmptyDataObject(thisCache) ) {
+				if ( !( pvt ? isEmptyDataObject : jQuery.isEmptyObject )( thisCache ) ) {
 					return;
 				}
 			}
 		}
 
 		// See jQuery.data for more information
-		if ( pvt ) {
-			delete cache[ id ][ internalKey ];
+		if ( !pvt ) {
+			delete cache[ id ].data;
 
 			// Don't destroy the parent cache unless the internal data object
 			// had been the only thing left in it
@@ -186,8 +184,6 @@ jQuery.extend({
 			}
 		}
 
-		var internalCache = cache[ id ][ internalKey ];
-
 		// Browsers that fail expando deletion also refuse to delete expandos on
 		// the window, but it will allow it on all other JS objects; other browsers
 		// don't care
@@ -198,23 +194,9 @@ jQuery.extend({
 			cache[ id ] = null;
 		}
 
-		// We destroyed the entire user cache at once because it's faster than
-		// iterating through each key, but we need to continue to persist internal
-		// data if it existed
-		if ( internalCache ) {
-			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
-			if ( !isNode ) {
-				cache[ id ].toJSON = jQuery.noop;
-			}
-
-			cache[ id ][ internalKey ] = internalCache;
-
-		// Otherwise, we need to eliminate the expando on the node to avoid
+		// We destroyed the cache and need to eliminate the expando on the node to avoid
 		// false lookups in the cache for entries that no longer exist
-		} else if ( isNode ) {
+		if ( isNode ) {
 			// IE does not allow us to delete expando properties from nodes,
 			// nor does it have a removeAttribute function on Document nodes;
 			// we must handle all of these cases
@@ -342,11 +324,14 @@ 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
+// checks a cache object for emptiness
 function isEmptyDataObject( obj ) {
 	for ( var name in obj ) {
+
+		// if the public data object is empty, the private is still empty
+		if ( name === "data" && jQuery.isEmptyObject( obj[name] ) ) {
+			continue;
+		}
 		if ( name !== "toJSON" ) {
 			return false;
 		}

src/event.js

@@ -247,11 +247,10 @@ jQuery.event = {
 				}
 
 				delete elemData.events;
-				delete elemData.handle;
 
-				if ( jQuery.isEmptyObject( elemData ) ) {
-					jQuery.removeData( elem, undefined, true );
-				}
+				// removeData also checks for emptiness and clears the expando if empty
+				// so use it instead of delete for this last property we touch here
+				jQuery.removeData( elem, "handle", true );
 			}
 		}
 	},
@@ -326,17 +325,14 @@ jQuery.event = {
 
 		// Handle a global trigger
 		if ( !elem ) {
+
 			// TODO: Stop taunting the data cache; remove global events and always attach to document
-			jQuery.each( jQuery.cache, function() {
-				// internalKey variable is just used to make it easier to find
-				// and potentially change this stuff later; currently it just
-				// points to jQuery.expando
-				var internalKey = jQuery.expando,
-					internalCache = this[ internalKey ];
-				if ( internalCache && internalCache.events && internalCache.events[ type ] ) {
-					jQuery.event.trigger( event, data, internalCache.handle.elem );
+			var cache = jQuery.cache;
+			for ( i in cache ) {
+				if ( cache[ i ].events && cache[ i ].events[ type ] ) {
+					jQuery.event.trigger( event, data, cache[ i ].handle.elem );
 				}
-			});
+			}
 			return;
 		}
 

src/manipulation.js

@@ -356,27 +356,26 @@ function cloneCopyEvent( src, dest ) {
 		return;
 	}
 
-	var internalKey = jQuery.expando,
-		oldData = jQuery.data( src ),
-		curData = jQuery.data( dest, oldData );
-
-	// Switch to use the internal data object, if it exists, for the next
-	// stage of data copying
-	if ( (oldData = oldData[ internalKey ]) ) {
-		var events = oldData.events;
-				curData = curData[ internalKey ] = jQuery.extend({}, oldData);
-
-		if ( events ) {
-			delete curData.handle;
-			curData.events = {};
-
-			for ( var type in events ) {
-				for ( var i = 0, l = events[ type ].length; i < l; i++ ) {
-					jQuery.event.add( dest, type + ( events[ type ][ i ].namespace ? "." : "" ) + events[ type ][ i ].namespace, events[ type ][ i ], events[ type ][ i ].data );
-				}
+	var type, i, l,
+		oldData = jQuery._data( src ),
+		curData = jQuery._data( dest, oldData ),
+		events = oldData.events;
+
+	if ( events ) {
+		delete curData.handle;
+		curData.events = {};
+
+		for ( type in events ) {
+			for ( i = 0, l = events[ type ].length; i < l; i++ ) {
+				jQuery.event.add( dest, type + ( events[ type ][ i ].namespace ? "." : "" ) + events[ type ][ i ].namespace, events[ type ][ i ], events[ type ][ i ].data );
 			}
 		}
 	}
+
+	// make the cloned public data object a copy from the original
+	if ( curData.data ) {
+		curData.data = jQuery.extend( {}, curData.data );
+	}
 }
 
 function cloneFixAttributes( src, dest ) {
@@ -706,7 +705,9 @@ jQuery.extend({
 	},
 
 	cleanData: function( elems ) {
-		var data, id, cache = jQuery.cache, internalKey = jQuery.expando, special = jQuery.event.special,
+		var data, id, 
+			cache = jQuery.cache,
+			special = jQuery.event.special,
 			deleteExpando = jQuery.support.deleteExpando;
 
 		for ( var i = 0, elem; (elem = elems[i]) != null; i++ ) {
@@ -717,7 +718,7 @@ jQuery.extend({
 			id = elem[ jQuery.expando ];
 
 			if ( id ) {
-				data = cache[ id ] && cache[ id ][ internalKey ];
+				data = cache[ id ];
 
 				if ( data && data.events ) {
 					for ( var type in data.events ) {

test/unit/data.js

@@ -7,7 +7,7 @@ test("expando", function(){
 });
 
 function dataTests (elem) {
-	// expect(32)
+	// expect(31)
 
 	function getCacheLength() {
 		var cacheLength = 0;
@@ -52,8 +52,8 @@ function dataTests (elem) {
 	equals( jQuery._data(elem, "foo"), "foo2", "Setting internal data works" );
 	equals( jQuery.data(elem, "foo"), "foo1", "Setting internal data does not override user data" );
 
-	var internalDataObj = jQuery.data(elem, jQuery.expando);
-	strictEqual( jQuery._data(elem), internalDataObj, "Internal data object is accessible via jQuery.expando property" );
+	var internalDataObj = jQuery._data( elem );
+	ok( internalDataObj, "Internal data object exists" );
 	notStrictEqual( dataObj, internalDataObj, "Internal data object is not the same as user data object" );
 
 	strictEqual( elem.boom, undefined, "Data is never stored directly on the object" );
@@ -62,7 +62,7 @@ function dataTests (elem) {
 	strictEqual( jQuery.data(elem, "foo"), undefined, "jQuery.removeData removes single properties" );
 
 	jQuery.removeData(elem);
-	strictEqual( jQuery.data(elem, jQuery.expando), internalDataObj, "jQuery.removeData does not remove internal data if it exists" );
+	strictEqual( jQuery._data(elem), internalDataObj, "jQuery.removeData does not remove internal data if it exists" );
 
 	jQuery.removeData(elem, undefined, true);
 
@@ -75,8 +75,9 @@ function dataTests (elem) {
 	jQuery.data(elem, "foo", "foo1");
 	equals( jQuery._data(elem, "foo"), "foo2", "Setting user data does not override internal data" );
 
-	jQuery.removeData(elem, undefined, true);
-	equals( jQuery.data(elem, "foo"), "foo1", "jQuery.removeData for internal data does not remove user data" );
+	// delete the last private data key so we can test removing public data
+	// will destroy the cache
+	jQuery.removeData( elem, "foo", true );
 
 	if (elem.nodeType) {
 		var oldCacheLength = getCacheLength();
@@ -138,7 +139,7 @@ function dataTests (elem) {
 }
 
 test("jQuery.data", function() {
-	expect(128);
+	expect(124);
 
 	var div = document.createElement("div");