Controlgroup: Add "only" position to class generator functions

Fixes #14972
Closes jquerygh-1711

Author: arschmitz

tests/unit/controlgroup/controlgroup.html

@@ -58,6 +58,16 @@
 		<label class="ui-controlgroup-label">Label</label>
 		<button>Button with icon on the bottom</button>
 	</div>
+	<div class="controlgroup-single-select">
+		<select id="select-single">
+			<option>Fast</option>
+			<option>Medium</option>
+			<option>Slow</option>
+		</select>
+	</div>
+	<div class="controlgroup-single-button">
+		<button class="single-button">button</button>
+	</div>
 </div>
 </body>
 </html>

tests/unit/controlgroup/core.js

@@ -100,4 +100,64 @@ QUnit.test( "_resolveClassesValues", function( assert ) {
 	assertSanatized( assert, "bar", "bar", "No corner classes" );
 } );
 
+QUnit.test( "Single controlgroup select - horizontal", function( assert ) {
+	assert.expect( 4 );
+	var group = $( ".controlgroup-single-select" ).controlgroup();
+	var select = group.find( ".ui-selectmenu-button" );
+
+	assert.hasClasses( select, "ui-corner-all" );
+	assert.lacksClasses( select,
+		"ui-corner-left ui-corner-right ui-corner-top ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+
+	group.find( "select" ).selectmenu( "open" );
+	assert.hasClasses( select, "ui-corner-top" );
+	assert.lacksClasses( select,
+		"ui-corner-left ui-corner-right ui-corner-all ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+} );
+
+QUnit.test( "Single controlgroup select - vertical", function( assert ) {
+	assert.expect( 4 );
+	var group = $( ".controlgroup-single-select" ).controlgroup( {
+		direction: "verticle"
+	} );
+	var select = group.find( ".ui-selectmenu-button" );
+
+	assert.hasClasses( select, "ui-corner-all" );
+	assert.lacksClasses( select,
+		"ui-corner-left ui-corner-right ui-corner-top ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+
+	group.find( "select" ).selectmenu( "open" );
+	assert.hasClasses( select, "ui-corner-top" );
+	assert.lacksClasses( select,
+		"ui-corner-left ui-corner-right ui-corner-all ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+} );
+
+QUnit.test( "Single controlgroup button - horizontal", function( assert ) {
+	assert.expect( 2 );
+	var group = $( ".controlgroup-single-button" ).controlgroup();
+	var button = group.find( "button" );
+
+	assert.hasClasses( button, "ui-corner-all" );
+	assert.lacksClasses( button,
+		"ui-corner-left ui-corner-right ui-corner-top ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+} );
+
+QUnit.test( "Single controlgroup button - vertical", function( assert ) {
+	assert.expect( 2 );
+	var group = $( ".controlgroup-single-button" ).controlgroup( {
+		direction: "verticle"
+	} );
+	var button = group.find( "button" );
+
+	assert.hasClasses( button, "ui-corner-all" );
+	assert.lacksClasses( button,
+		"ui-corner-left ui-corner-right ui-corner-top ui-corner-left" +
+		" ui-corner-tr ui-corner-tl ui-corner-bl ui corner-br" );
+} );
+
 } );

ui/widgets/controlgroup.js

@@ -152,7 +152,7 @@ return $.widget( "ui.controlgroup", {
 	},
 
 	_updateCornerClass: function( element, position ) {
-		var remove = "ui-corner-top ui-corner-bottom ui-corner-left ui-corner-right";
+		var remove = "ui-corner-top ui-corner-bottom ui-corner-left ui-corner-right ui-corner-all";
 		var add = this._buildSimpleOptions( position, "label" ).classes.label;
 
 		this._removeClass( element, null, remove );
@@ -167,7 +167,8 @@ return $.widget( "ui.controlgroup", {
 		result.classes[ key ] = {
 			"middle": "",
 			"first": "ui-corner-" + ( direction ? "top" : "left" ),
-			"last": "ui-corner-" + ( direction ? "bottom" : "right" )
+			"last": "ui-corner-" + ( direction ? "bottom" : "right" ),
+			"only": "ui-corner-all"
 		}[ position ];
 
 		return result;
@@ -206,6 +207,10 @@ return $.widget( "ui.controlgroup", {
 				last: {
 					"ui-selectmenu-button-open": direction ? "" : "ui-corner-tr",
 					"ui-selectmenu-button-closed": "ui-corner-" + ( direction ? "bottom" : "right" )
+				},
+				only: {
+					"ui-selectmenu-button-open": "ui-corner-top",
+					"ui-selectmenu-button-closed": "ui-corner-all"
 				}
 
 			}[ position ]
@@ -261,7 +266,9 @@ return $.widget( "ui.controlgroup", {
 				var instance = children[ value ]().data( "ui-controlgroup-data" );
 
 				if ( instance && that[ "_" + instance.widgetName + "Options" ] ) {
-					var options = that[ "_" + instance.widgetName + "Options" ]( value );
+					var options = that[ "_" + instance.widgetName + "Options" ](
+						children.length === 1 ? "only" : value
+					);
 					options.classes = that._resolveClassesValues( options.classes, instance );
 					instance.element[ instance.widgetName ]( options );
 				} else {