Selector: Make empty attribute selectors work in IE again

qSA in IE 11/Edge often (but not always) don't find elements with an empty
name attribute selector (`[name=""]`). Detect that & fall back to Sizzle
traversal.

Interestingly, IE 10 & older don't seem to have the issue.

Fixes gh-4435
Closes gh-4510

src/selector.js

@@ -5,6 +5,7 @@ import documentElement from "./var/documentElement.js";
 import indexOf from "./var/indexOf.js";
 import pop from "./var/pop.js";
 import push from "./var/push.js";
+import whitespace from "./selector/var/whitespace.js";
 import rbuggyQSA from "./selector/rbuggyQSA.js";
 import support from "./selector/support.js";
 
@@ -41,9 +42,6 @@ var i,
 
 	// Regular expressions
 
-	// https://www.w3.org/TR/css3-selectors/#whitespace
-	whitespace = "[\\x20\\t\\r\\n\\f]",
-
 	// https://www.w3.org/TR/css-syntax-3/#ident-token-diagram
 	identifier = "(?:\\\\[\\da-fA-F]{1,6}" + whitespace +
 		"?|\\\\[^\\r\\n\\f]|[\\w-]|[^\0-\\x7f])+",

src/selector/rbuggyQSA.js

@@ -1,8 +1,10 @@
 import document from "../var/document.js";
 import isIE from "../var/isIE.js";
+import whitespace from "./var/whitespace.js";
 
 var rbuggyQSA = [],
-	testEl = document.createElement( "div" );
+	testEl = document.createElement( "div" ),
+	input = document.createElement( "input" );
 
 testEl.innerHTML = "<a href=''></a>";
 
@@ -19,6 +21,18 @@ if ( isIE ) {
 	rbuggyQSA.push( ":enabled", ":disabled" );
 }
 
+// Support: IE 11+, Edge 15 - 18+
+// IE 11/Edge don't find elements on a `[name='']` query in some cases.
+// Adding a temporary attribute to the document before the selection works
+// around the issue.
+// Interestingly, IE 10 & older don't seem to have the issue.
+input.setAttribute( "name", "" );
+testEl.appendChild( input );
+if ( !testEl.querySelectorAll( "[name='']" ).length ) {
+	rbuggyQSA.push( "\\[" + whitespace + "*name" + whitespace + "*=" +
+		whitespace + "*(?:''|\"\")" );
+}
+
 rbuggyQSA = rbuggyQSA.length && new RegExp( rbuggyQSA.join( "|" ) );
 
 export default rbuggyQSA;

src/selector/var/whitespace.js

@@ -0,0 +1,2 @@
+// https://www.w3.org/TR/css3-selectors/#whitespace
+export default "[\\x20\\t\\r\\n\\f]";

test/data/qunit-fixture.html

@@ -116,6 +116,11 @@ Z</textarea>
 	<input type="radio" name="R1" value="2" />
 	<input type="text" name="My Name" value="me" />
 	<input type="reset" name="reset" value="NO" />
+	<div class="empty-name-container">
+		<div id="empty-name-parent">
+			<input type="text" id="name-empty" name="" value="" />
+		</div>
+	</div>
 	<select name="S1">
 		<option value="abc">ABC</option>
 		<option value="abc">ABC</option>

test/unit/attributes.js

@@ -1255,7 +1255,7 @@ QUnit.test( "addClass(Array)", function( assert ) {
 } );
 
 QUnit.test( "addClass(Function) with incoming value", function( assert ) {
-	assert.expect( 57 );
+	assert.expect( 59 );
 	var pass, i,
 		div = jQuery( "#qunit-fixture div" ),
 		old = div.map( function() {
@@ -1330,7 +1330,7 @@ QUnit.test( "removeClass(Array) - simple", function( assert ) {
 } );
 
 QUnit.test( "removeClass(Function) with incoming value", function( assert ) {
-	assert.expect( 57 );
+	assert.expect( 59 );
 
 	var $divs = jQuery( "#qunit-fixture div" ).addClass( "test" ), old = $divs.map( function() {
 		return jQuery( this ).attr( "class" );

test/unit/selector.js

@@ -720,7 +720,7 @@ QUnit.test( "attributes - special characters", function( assert ) {
 } );
 
 QUnit.test( "attributes - others", function( assert ) {
-	assert.expect( 10 );
+	assert.expect( 14 );
 
 	var div = document.getElementById( "foo" );
 
@@ -750,6 +750,17 @@ QUnit.test( "attributes - others", function( assert ) {
 	assert.ok( !jQuery( "<input type='checkbox'/>" ).prop( "checked", true ).is( "[checked]" ),
 		"[checked] selects by attribute (negative)"
 	);
+
+	assert.t( "empty name", "[name='']", [ "name-empty" ] );
+	assert.t( "prefixed empty name", "#empty-name-parent [name='']", [ "name-empty" ] );
+
+	var emptyNameContainer = jQuery( ".empty-name-container" );
+	assert.deepEqual( emptyNameContainer.find( "[name='']" ).get(),
+		q( "name-empty" ),
+		"empty name with context" );
+	assert.deepEqual( emptyNameContainer.find( "#empty-name-parent [name='']" ).get(),
+		q( "name-empty" ),
+		"prefixed empty name with context" );
 } );
 
 QUnit.test( "pseudo - (parent|empty)", function( assert ) {
@@ -1257,7 +1268,7 @@ QUnit[ QUnit.jQuerySelectorsPos ? "test" : "skip" ]( "pseudo - position", functi
 
 	assert.t( "Check element position", "#qunit-fixture div div:eq(0)", [ "nothiddendivchild" ] );
 	assert.t( "Check element position", "#select1 option:eq(3)", [ "option1d" ] );
-	assert.t( "Check element position", "#qunit-fixture div div:eq(10)", [ "names-group" ] );
+	assert.t( "Check element position", "#qunit-fixture div div:eq(10)", [ "no-clone-exception" ] );
 	assert.t( "Check element position", "#qunit-fixture div div:first", [ "nothiddendivchild" ] );
 	assert.t( "Check element position", "#qunit-fixture div > div:first", [ "nothiddendivchild" ] );
 	assert.t( "Check element position", "#qunit-fixture div:first a:first", [ "yahoo" ] );