CSS: Don't cache unrecognized CSS property names

This prevents jQuery from caching a prefixed property name if provided
directly by the user, e.g. the following code:

	elem.css( "msTransform", "translate(5px, 2px)" );

should not prevent one from from later setting the transition directly:

	elem.css( "transform", "translate(5px, 2px)" );

on a browser not understanding the unprefixed version which is the case
for Safari 8 & transform.

(cherry-picked from d471842b3e)

Fixes gh-2015
Closes gh-2298

src/css.js

@@ -39,32 +39,30 @@ var
 		fontWeight: "400"
 	},
 
-	cssPrefixes = [ "Webkit", "Moz", "ms" ];
+	cssPrefixes = [ "Webkit", "Moz", "ms" ],
+	emptyStyle = document.createElement( "div" ).style;
 
 // BuildExclude
 curCSS = curCSS.curCSS;
 
 // return a css property mapped to a potentially vendor prefixed property
-function vendorPropName( style, name ) {
+function vendorPropName( name ) {
 
 	// shortcut for names that are not vendor prefixed
-	if ( name in style ) {
+	if ( name in emptyStyle ) {
 		return name;
 	}
 
 	// check for vendor prefixed names
 	var capName = name[ 0 ].toUpperCase() + name.slice( 1 ),
-		origName = name,
 		i = cssPrefixes.length;
 
 	while ( i-- ) {
 		name = cssPrefixes[ i ] + capName;
-		if ( name in style ) {
+		if ( name in emptyStyle ) {
 			return name;
 		}
 	}
-
-	return origName;
 }
 
 function setPositiveNumber( elem, value, subtract ) {
@@ -209,7 +207,7 @@ jQuery.extend({
 			style = elem.style;
 
 		name = jQuery.cssProps[ origName ] ||
-			( jQuery.cssProps[ origName ] = vendorPropName( style, origName ) );
+			( jQuery.cssProps[ origName ] = vendorPropName( origName ) || origName );
 
 		// gets hook for the prefixed version
 		// followed by the unprefixed version
@@ -273,7 +271,7 @@ jQuery.extend({
 
 		// Make sure that we're working with the right name
 		name = jQuery.cssProps[ origName ] ||
-			( jQuery.cssProps[ origName ] = vendorPropName( elem.style, origName ) );
+			( jQuery.cssProps[ origName ] = vendorPropName( origName ) || origName );
 
 		// gets hook for the prefixed version
 		// followed by the unprefixed version

test/unit/css.js

@@ -1187,4 +1187,84 @@ test( "get upper case alpha opacity in IE8", 1, function() {
 	fixture.removeChild( div );
 });
 
+
+( function() {
+	var vendorPrefixes = [ "Webkit", "Moz", "ms" ];
+
+	function resetCssPropsFor( name ) {
+		delete jQuery.cssProps[ name ];
+		jQuery.each( vendorPrefixes, function( index, prefix ) {
+			delete jQuery.cssProps[ prefix + name[ 0 ].toUpperCase() + name.slice( 1 ) ];
+		} );
+	}
+
+	test( "Don't default to a cached previously used wrong prefixed name (gh-2015)", function() {
+		// Note: this test needs a property we know is only supported in a prefixed version
+		// by at least one of our main supported browsers. This may get out of date so let's
+		// use -(webkit|moz)-appearance as well as those two are not on a standards track.
+		var appearanceName, transformName, elem, elemStyle,
+			transformVal = "translate(5px, 2px)",
+			emptyStyle = document.createElement( "div" ).style;
+
+		if ( "appearance" in emptyStyle ) {
+			appearanceName = "appearance";
+		} else {
+			jQuery.each( vendorPrefixes, function( index, prefix ) {
+				var prefixedProp = prefix + "Appearance";
+				if ( prefixedProp in emptyStyle ) {
+					appearanceName = prefixedProp;
+				}
+			} );
+		}
+
+		if ( "transform" in emptyStyle ) {
+			transformName = "transform";
+		} else {
+			jQuery.each( vendorPrefixes, function( index, prefix ) {
+				var prefixedProp = prefix + "Transform";
+				if ( prefixedProp in emptyStyle ) {
+					transformName = prefixedProp;
+				}
+			} );
+		}
+
+		expect( !!appearanceName + !!transformName + 1 );
+
+		resetCssPropsFor( "appearance" );
+		resetCssPropsFor( "transform" );
+
+		elem = jQuery( "<div/>" )
+			.css( {
+				msAppearance: "none",
+				appearance: "none",
+
+				// Only the ms prefix is used to make sure we haven't e.g. set
+				// webkitTransform ourselves in the test.
+				msTransform: transformVal,
+				transform: transformVal
+			} );
+		elemStyle = elem[ 0 ].style;
+
+		if ( appearanceName ) {
+			equal( elemStyle[ appearanceName ], "none", "setting properly-prefixed appearance" );
+		}
+		if ( transformName ) {
+			equal( elemStyle[ transformName ], transformVal, "setting properly-prefixed transform" );
+		}
+		equal( elemStyle[ "undefined" ], undefined, "Nothing writes to node.style.undefined" );
+	} );
+
+	test( "Don't detect fake set properties on a node when caching the prefixed version", function() {
+		expect( 1 );
+
+		var elem = jQuery( "<div/>" ),
+			style = elem[ 0 ].style;
+		style.MozFakeProperty = "old value";
+		elem.css( "fakeProperty", "new value" );
+
+		equal( style.MozFakeProperty, "old value", "Fake prefixed property is not cached" );
+	} );
+
+} )();
+
 }