Widget: instance() should return undefined for empty sets

Fixes #15019

tests/unit/widget/core.js

@@ -786,7 +786,7 @@ QUnit.test( ".widget() - overriden", function( assert ) {
 } );
 
 QUnit.test( ".instance()", function( assert ) {
-	assert.expect( 2 );
+	assert.expect( 3 );
 	var div;
 
 	$.widget( "ui.testWidget", {
@@ -794,9 +794,11 @@ QUnit.test( ".instance()", function( assert ) {
 	} );
 
 	div = $( "<div>" );
-	assert.equal( div.testWidget( "instance" ), undefined );
+	assert.equal( div.testWidget( "instance" ), undefined, "uninitialized" );
 	div.testWidget();
-	assert.equal( div.testWidget( "instance" ), div.testWidget( "instance" ) );
+	assert.equal( div.testWidget( "instance" ), div.testWidget( "instance" ), "initialized" );
+
+	assert.equal( $().testWidget( "instance" ), undefined, "empty set" );
 } );
 
 QUnit.test( "._on() to element (default)", function( assert ) {

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