From 3dd8a09b441d65445f2b6a7c73e72af65445d5da Mon Sep 17 00:00:00 2001
From: =?utf8?q?Scott=20Gonz=C3=A1lez?= <scott.gonzalez@gmail.com>
Date: Thu, 4 Aug 2016 09:04:16 -0400
Subject: [PATCH] Widget: `instance()` should return `undefined` for empty sets

Fixes #15019
---
 tests/unit/widget/core.js |  8 +++---
 ui/widget.js              | 55 ++++++++++++++++++++++-----------------
 2 files changed, 36 insertions(+), 27 deletions(-)

diff --git a/tests/unit/widget/core.js b/tests/unit/widget/core.js
index 00dcb1611..d6bb3efb8 100644
--- a/tests/unit/widget/core.js
+++ b/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 ) {
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
-- 
2.39.5