Data: find hyphenated data with camelCased key

Fixes gh-2779

src/data.js

@@ -123,7 +123,12 @@ jQuery.fn.extend( {
 
 				// Attempt to get data from the cache
 				// with the key as-is
-				data = dataUser.get( elem, key );
+				data = dataUser.get( elem, key ) ||
+
+					// Try to find dashed key if it exists (gh-2779)
+					// This is for 2.2.x only
+					dataUser.get( elem, key.replace( rmultiDash, "-$&" ).toLowerCase() );
+
 				if ( data !== undefined ) {
 					return data;
 				}

test/unit/data.js

@@ -878,3 +878,12 @@ QUnit.test( ".data(prop) does not create expando", function( assert ) {
 		}
 	}
 } );
+
+QUnit.test( ".data(camelCase) retrieves hyphenated keys", function( assert ) {
+	assert.expect( 1 );
+
+	var div = jQuery( "<div/>" );
+
+	$.data( div[ 0 ], "data-test", "data" );
+	assert.equal( div.data( "dataTest" ), "data" );
+} );