Selector: Implement the uniqueSort chainable method

Some APIs, like `.prevAll()`, return elements in the reversed order, causing
confusing behavior when used with wrapping methods (see gh-5149 for more info)
 To provide an easy workaround, this commit implements a chainable `uniqueSort`
method on jQuery objects, an equivalent of `jQuery.uniqueSort`.

Fixes gh-5166
Closes gh-5168

(cherry picked from commit 5266f23cf4)

src/selector-native.js

@@ -4,11 +4,12 @@ define( [
 	"./var/documentElement",
 	"./var/hasOwn",
 	"./var/indexOf",
+	"./var/slice",
 
 	// The following utils are attached directly to the jQuery object.
 	"./selector/contains",
 	"./selector/escapeSelector"
-], function( jQuery, document, documentElement, hasOwn, indexOf ) {
+], function( jQuery, document, documentElement, hasOwn, indexOf, slice ) {
 
 "use strict";
 
@@ -164,6 +165,10 @@ jQuery.extend( {
 	}
 } );
 
+jQuery.fn.uniqueSort = function() {
+	return this.pushStack( jQuery.uniqueSort( slice.apply( this ) ) );
+};
+
 jQuery.extend( jQuery.find, {
 	matches: function( expr, elements ) {
 		return jQuery.find( expr, null, null, elements );

src/selector.js

@@ -931,6 +931,10 @@ jQuery.uniqueSort = function( results ) {
 	return results;
 };
 
+jQuery.fn.uniqueSort = function() {
+	return this.pushStack( jQuery.uniqueSort( slice.apply( this ) ) );
+};
+
 Expr = jQuery.expr = {
 
 	// Can be adjusted by the user

test/unit/selector.js

@@ -1959,22 +1959,8 @@ QUnit.test( "find in document fragments", function( assert ) {
 	assert.strictEqual( elem.length, 1, "Selection works" );
 } );
 
-QUnit.test( "jQuery.uniqueSort", function( assert ) {
-	assert.expect( 14 );
-
-	function Arrayish( arr ) {
-		var i = this.length = arr.length;
-		while ( i-- ) {
-			this[ i ] = arr[ i ];
-		}
-	}
-	Arrayish.prototype = {
-		slice: [].slice,
-		sort: [].sort,
-		splice: [].splice
-	};
-
-	var i, tests,
+function getUniqueSortFixtures() {
+	var i,
 		detached = [],
 		body = document.body,
 		fixture = document.getElementById( "qunit-fixture" ),
@@ -1989,7 +1975,7 @@ QUnit.test( "jQuery.uniqueSort", function( assert ) {
 		detached2.appendChild( document.createElement( "li" ) ).id = "detachedChild" + i;
 	}
 
-	tests = {
+	return {
 		"Empty": {
 			input: [],
 			expected: []
@@ -2030,15 +2016,63 @@ QUnit.test( "jQuery.uniqueSort", function( assert ) {
 			length: 3
 		}
 	};
+}
 
-	jQuery.each( tests, function( label, test ) {
-		var length = test.length || test.input.length;
-		// We duplicate `test.input` because otherwise it is modified by `uniqueSort`
+QUnit.test( "jQuery.uniqueSort", function( assert ) {
+	assert.expect( 14 );
+
+	var fixtures = getUniqueSortFixtures();
+
+	function Arrayish( arr ) {
+		var i = this.length = arr.length;
+		while ( i-- ) {
+			this[ i ] = arr[ i ];
+		}
+	}
+	Arrayish.prototype = {
+		slice: [].slice,
+		sort: [].sort,
+		splice: [].splice
+	};
+
+	jQuery.each( fixtures, function( label, fixture ) {
+		var length = fixture.length || fixture.input.length;
+
+		// We duplicate `fixture.input` because otherwise it is modified by `uniqueSort`
 		// and the second test becomes worthless.
-		assert.deepEqual( jQuery.uniqueSort( test.input.slice( 0 ) ).slice( 0, length ),
-			test.expected, label + " (array)" );
-		assert.deepEqual( jQuery.uniqueSort( new Arrayish( test.input ) ).slice( 0, length ),
-			test.expected, label + " (quasi-array)" );
+		assert.deepEqual(
+			jQuery.uniqueSort( fixture.input.slice( 0 ) )
+				.slice( 0, length ),
+			fixture.expected,
+			label + " (array)"
+		);
+
+		assert.deepEqual(
+			jQuery.uniqueSort( new Arrayish( fixture.input ) )
+				.slice( 0, length ),
+			fixture.expected,
+			label + " (quasi-array)"
+		);
+	} );
+} );
+
+QUnit.test( "uniqueSort()", function( assert ) {
+	assert.expect( 28 );
+
+	var fixtures = getUniqueSortFixtures();
+
+	jQuery.each( fixtures, function( label, fixture ) {
+		var length = fixture.length || fixture.input.length,
+			fixtureInputCopy = fixture.input.slice( 0 ),
+			sortedElem = jQuery( fixture.input ).uniqueSort();
+
+		assert.deepEqual( fixture.input, fixtureInputCopy, "Fixture not modified (" + label + ")" );
+
+		assert.deepEqual( sortedElem.slice( 0, length ).toArray(), fixture.expected, label );
+
+		// Chaining
+		assert.ok( sortedElem instanceof jQuery, "chaining" );
+		assert.deepEqual( sortedElem.end().toArray(), fixture.input, label );
 	} );
 } );