Widget: `instance()` should return `undefined` for empty sets

Fixes #15019

1 files changed, 31 insertions, 24 deletions

diff --git a/ui/widget.js b/ui/widget.js
index c82b95326..06a3ce88e 100644
--- a/ui/widget.js
+++ b/ui/widget.js
@@ -215,35 +215,42 @@ $.widget.bridge = function( name, object ) {
 		var returnValue = this;
 
 		if ( isMethodCall ) {
-			this.each( function() {
-				var methodValue;
-				var instance = $.data( this, fullName );
 
-				if ( options === "instance" ) {
-					returnValue = instance;
-					return false;
-				}
+			// If this is an empty collection, we need to have the instance method
+			// return undefined instead of the jQuery instance
+			if ( !this.length && options === "instance" ) {
+				returnValue = undefined;
+			} else {
+				this.each( function() {
+					var methodValue;
+					var instance = $.data( this, fullName );
 
-				if ( !instance ) {
-					return $.error( "cannot call methods on " + name +
-						" prior to initialization; " +
-						"attempted to call method '" + options + "'" );
-				}
+					if ( options === "instance" ) {
+						returnValue = instance;
+						return false;
+					}
 
-				if ( !$.isFunction( instance[ options ] ) || options.charAt( 0 ) === "_" ) {
-					return $.error( "no such method '" + options + "' for " + name +
-						" widget instance" );
-				}
+					if ( !instance ) {
+						return $.error( "cannot call methods on " + name +
+							" prior to initialization; " +
+							"attempted to call method '" + options + "'" );
+					}
 
-				methodValue = instance[ options ].apply( instance, args );
+					if ( !$.isFunction( instance[ options ] ) || options.charAt( 0 ) === "_" ) {
+						return $.error( "no such method '" + options + "' for " + name +
+							" widget instance" );
+					}
 
-				if ( methodValue !== instance && methodValue !== undefined ) {
-					returnValue = methodValue && methodValue.jquery ?
-						returnValue.pushStack( methodValue.get() ) :
-						methodValue;
-					return false;
-				}
-			} );
+					methodValue = instance[ options ].apply( instance, args );
+
+					if ( methodValue !== instance && methodValue !== undefined ) {
+						returnValue = methodValue && methodValue.jquery ?
+							returnValue.pushStack( methodValue.get() ) :
+							methodValue;
+						return false;
+					}
+				} );
+			}
 		} else {
 
 			// Allow multiple hashes to be passed on init