feat(landmark-no-more-than-one-banner): add rule ensuring no more than one banner

Author: sulsanaul

doc/rule-descriptions.md

@@ -34,6 +34,7 @@
 | label-title-only | Ensures that every form element is not solely labeled using the title or aria-describedby attributes | cat.forms, best-practice | true |
 | label | Ensures every form element has a label | cat.forms, wcag2a, wcag332, wcag131, section508, section508.22.n | true |
 | landmark-main-is-top-level | The main landmark should not be contained in another landmark | best-practice | true |
+| landmark-no-more-than-one-banner | A banner landmark identifies site-oriented content at the beginning of each page within a website | best-practice | true |
 | landmark-one-main | Ensures a navigation point to the primary content of the page. If the page contains iframes, each iframe should contain either no main landmarks or just one. | best-practice | true |
 | layout-table | Ensures presentational <table> elements do not use <th>, <caption> elements or the summary attribute | cat.semantics, wcag2a, wcag131 | true |
 | link-in-text-block | Links can be distinguished without relying on color | cat.color, experimental, wcag2a, wcag141 | true |

lib/checks/keyboard/has-no-more-than-one-banner.js

@@ -0,0 +1,29 @@
+const banners = axe.utils.querySelectorAll(virtualNode, 'header, [role=banner]');
+const sectioning = ['main', 'section', 'aside', 'nav', 'article'];
+var count = 0;
+
+function isBanner(node){
+  var parent = axe.commons.dom.getComposedParent(node);
+  while (parent){
+    if (sectioning.includes(parent.tagName.toLowerCase())){
+      return false;
+    }
+    parent = axe.commons.dom.getComposedParent(parent);
+  }
+  return true;
+}
+
+for (var i=0; i<banners.length; i++){
+  var node = banners[i].actualNode;
+  var role = node.getAttribute('role');
+  if (!!role){
+    role = role.toLowerCase();
+  }
+  if (role==='banner' || isBanner(node)){
+    count++;
+  }
+  if (count>1){
+    return false;
+  }
+}
+return true;

lib/checks/keyboard/has-no-more-than-one-banner.json

@@ -0,0 +1,11 @@
+{
+	"id": "has-no-more-than-one-banner",
+	"evaluate": "has-no-more-than-one-banner.js",
+	"metadata": {
+		"impact": "moderate",
+		"messages": {
+		"pass": "Document has no more than one banner landmark",
+		"fail": "Document has more than one banner landmark"
+		}
+	}
+}

lib/rules/landmark-no-more-than-one-banner.json

@@ -0,0 +1,16 @@
+{
+  "id": "landmark-no-more-than-one-banner",
+  "selector": "html",
+  "tags": [
+    "best-practice"
+  ],
+  "metadata": {
+    "description": "A banner landmark identifies site-oriented content at the beginning of each page within a website",
+    "help": "Page must not contain more than one banner landmark"
+  },
+  "all": [],
+  "any": [
+    "has-no-more-than-one-banner"
+  ],
+  "none": []
+}

test/checks/keyboard/has-no-more-than-one-banner.js

@@ -0,0 +1,50 @@
+describe('has-no-more-than-one-banner', function () {
+	'use strict';
+
+	var fixture = document.getElementById('fixture');
+	var checkContext = new axe.testUtils.MockCheckContext();
+	var checkSetup = axe.testUtils.checkSetup;
+	var shadowCheckSetup = axe.testUtils.shadowCheckSetup;
+	var shadowSupported = axe.testUtils.shadowSupport.v1;
+
+	afterEach(function () {
+		fixture.innerHTML = '';
+		checkContext.reset();
+	});
+
+	it('should return false if there is more than one element with role banner', function () {
+		var params = checkSetup('<div id="target"><div role="banner"></div><div role="banner"></div></div>');
+		assert.isFalse(checks['has-no-more-than-one-banner'].evaluate.apply(checkContext, params));
+
+	});
+
+	it('should return false if there is more than one header serving as a banner', function () {
+		var params = checkSetup('<div id="target"><header></header><header></header></div>');
+		assert.isFalse(checks['has-no-more-than-one-banner'].evaluate.apply(checkContext, params));
+	});
+
+	it('should return true if there are multiple headers contained in sectioning elements', function(){
+		var params = checkSetup('<div role="main" id="target"><header></header><header></header></div>');
+		assert.isTrue(checks['has-no-more-than-one-main'].evaluate.apply(checkContext, params));
+	});
+
+	it('should return true if there is only one element with role banner', function(){
+		var params = checkSetup('<div role="banner" id="target"></div>');
+		assert.isTrue(checks['has-no-more-than-one-banner'].evaluate.apply(checkContext, params));
+	});
+
+	it('should return true if there is only one header serving as a banner', function(){
+		var params = checkSetup('<header id="target"></header>');
+		assert.isTrue(checks['has-no-more-than-one-banner'].evaluate.apply(checkContext, params));
+	});
+
+	(shadowSupported ? it : xit)
+	('should return false if there is a second banner inside the shadow dom', function () {
+		var params = shadowCheckSetup(
+			'<div role="banner" id="target"></div>',
+			'<div role="banner"></div>'
+		);
+		assert.isFalse(checks['has-no-more-than-one-banner'].evaluate.apply(checkContext, params));
+	});
+
+});

test/integration/full/landmark-no-more-than-one-banner/frames/level1-fail.html

@@ -0,0 +1,16 @@
+<!doctype html>
+<html lang="en" id="fail2">
+<head>
+	<meta charset="utf8">
+	<script src="/axe.js"></script>
+</head>
+<body>
+	<header>
+		Header 1
+	</header>
+	<header>
+		Header 2
+	</header>
+	<iframe id="frame2" src="level2.html"></iframe>
+</body>
+</html>

test/integration/full/landmark-no-more-than-one-banner/frames/level1.html

@@ -0,0 +1,17 @@
+<!doctype html>
+<html lang="en" id="pass2">
+<head>
+	<meta charset="utf8">
+	<script src="/axe.js"></script>
+</head>
+<body>
+	<main>
+		<header>
+			Header 1 contained in main landmark
+		</header>
+		<header>
+			Header 2 contained in main landmark
+		</header>
+	</main>
+</body>
+</html>

test/integration/full/landmark-no-more-than-one-banner/frames/level2.html

@@ -0,0 +1,17 @@
+<!doctype html>
+<html lang="en" id="fail3">
+<head>
+	<meta charset="utf8">
+	<script src="/axe.js"></script>
+</head>
+<body>
+	<main>
+    <div role="banner">
+      Div 1 with role banner in main landmark
+    </div>
+    <div role="banner">
+      Div 2 with role banner in main landmark
+    </div>
+  </main>
+</body>
+</html>

test/integration/full/landmark-no-more-than-one-banner/landmark-no-more-than-one-banner-fail.html

@@ -0,0 +1,29 @@
+<!doctype html>
+<html lang="en" id="fail1">
+<head>
+	<meta charset="utf8">
+	<link rel="stylesheet" type="text/css" href="/node_modules/mocha/mocha.css" />
+	<script src="/node_modules/mocha/mocha.js"></script>
+	<script src="/node_modules/chai/chai.js"></script>
+	<script src="/axe.js"></script>
+	<script>
+		mocha.setup({
+			timeout: 10000,
+			ui: 'bdd'
+		});
+		var assert = chai.assert;
+	</script>
+</head>
+<body>
+	<div role="banner">
+		Div 1 with role of "banner"
+	</div>
+	<div role="banner">
+		Div 2 with role of "banner"
+	</div>
+	<iframe id="frame1" src="frames/level1-fail.html"></iframe>
+	<div id="mocha"></div>
+	<script src="landmark-no-more-than-one-banner-fail.js"></script>
+	<script src="/test/integration/adapter.js"></script>
+</body>
+</html>

test/integration/full/landmark-no-more-than-one-banner/landmark-no-more-than-one-banner-fail.js

@@ -0,0 +1,51 @@
+describe('landmark-no-more-than-one-banner test failure', function () {
+	'use strict';
+	var results;
+	before(function (done) {
+		function start() {
+			axe.run({ runOnly: { type: 'rule', values: ['landmark-no-more-than-one-banner'] } }, function (err, r) {
+				assert.isNull(err);
+				results = r;
+				done();
+			});
+		}
+		if (document.readyState !== 'complete') {
+			window.addEventListener('load', start);
+		} else {
+			start();
+		}
+	});
+
+	describe('violations', function () {
+		it('should find 3', function () {
+			assert.lengthOf(results.violations[0].nodes, 3);
+		});
+
+		it('should find #fail1', function () {
+			assert.deepEqual(results.violations[0].nodes[0].target, ['#fail1']);
+		});
+
+		it('should find #frame1, #fail2', function () {
+			assert.deepEqual(results.violations[0].nodes[1].target, ['#frame1', '#fail2']);
+		});
+
+		it('should find #frame1, #frame2, #fail3', function () {
+			assert.deepEqual(results.violations[0].nodes[2].target, ['#frame1', '#frame2', '#fail3']);
+		});
+
+	});
+
+	describe('passes', function () {
+		it('should find 0', function () {
+			assert.lengthOf(results.passes, 0);
+		});
+	});
+
+	it('should find 0 inapplicable', function () {
+		assert.lengthOf(results.inapplicable, 0);
+	});
+
+	it('should find 0 incomplete', function () {
+		assert.lengthOf(results.incomplete, 0);
+	});
+});