fix(skip-link): work with absolute and relative paths

lib/commons/dom/get-element-by-reference.js

@@ -1,3 +1,5 @@
+import isCurrentPageLink from './is-current-page-link';
+
 /**
  * Returns a reference to the element matching the attr URL fragment value
  * @method getElementByReference
@@ -13,10 +15,12 @@ function getElementByReference(node, attr) {
     return null;
   }
 
-  if (fragment.charAt(0) === '#') {
-    fragment = decodeURIComponent(fragment.substring(1));
-  } else if (fragment.substr(0, 2) === '/#') {
-    fragment = decodeURIComponent(fragment.substring(2));
+  if (attr === 'href' && !isCurrentPageLink(node)) {
+    return null;
+  }
+
+  if (fragment.indexOf('#') !== -1) {
+    fragment = decodeURIComponent(fragment.substr(fragment.indexOf('#') + 1));
   }
 
   let candidate = document.getElementById(fragment);

lib/commons/dom/index.js

@@ -19,6 +19,7 @@ export { default as hasContentVirtual } from './has-content-virtual';
 export { default as hasContent } from './has-content';
 export { default as idrefs } from './idrefs';
 export { default as insertedIntoFocusOrder } from './inserted-into-focus-order';
+export { default as isCurrentPageLink } from './is-current-page-link';
 export { default as isFocusable } from './is-focusable';
 export { default as isHiddenWithCSS } from './is-hidden-with-css';
 export { default as isHTML5 } from './is-html5';

lib/commons/dom/is-current-page-link.js

@@ -0,0 +1,66 @@
+// angular skip links start with /#
+const angularSkipLinkRegex = /^\/\#/;
+
+// angular router link uses #! or #/
+const angularRouterLinkRegex = /^#[!/]/;
+
+/**
+ * Determine if an anchor elements href attribute references the current page.
+ * @method isCurrentPageLink
+ * @memberof axe.commons.dom
+ * @param {HTMLAnchorElement} anchor
+ * @return {Boolean|null}
+ */
+export default function isCurrentPageLink(anchor) {
+  const href = anchor.getAttribute('href');
+  if (!href || href === '#') {
+    return false;
+  }
+
+  if (angularSkipLinkRegex.test(href)) {
+    return true;
+  }
+
+  const { hash, protocol, hostname, port, pathname } = anchor;
+  if (angularRouterLinkRegex.test(hash)) {
+    return false;
+  }
+
+  if (href.charAt(0) === '#') {
+    return true;
+  }
+
+  // jsdom can have window.location.origin set to "null" (the string)
+  // if the url option is not set when parsing the dom string
+  if (
+    typeof window.location?.origin !== 'string' ||
+    window.location.origin.indexOf('://') === -1
+  ) {
+    return null;
+  }
+
+  // ie11 does not support window.origin
+  const currentPageUrl = window.location.origin + window.location.pathname;
+
+  // ie11 does not have anchor.origin so we need to construct
+  // it ourselves
+  // also ie11 has empty protocol, hostname, and port when the
+  // link is relative, so use window.location.origin in these cases
+  let url;
+  if (!hostname) {
+    url = window.location.origin;
+  } else {
+    url = `${protocol}//${hostname}${port ? `:${port}` : ''}`;
+  }
+
+  // ie11 has empty pathname if link is just a hash, so use
+  // window.location.pathname in these cases
+  if (!pathname) {
+    url += window.location.pathname;
+  } else {
+    // ie11 pathname does not start with / but chrome and firefox do
+    url += (pathname[0] !== '/' ? '/' : '') + pathname;
+  }
+
+  return url === currentPageUrl;
+}

lib/commons/dom/is-skip-link.js

@@ -1,34 +1,43 @@
 import cache from '../../core/base/cache';
 import { querySelectorAll } from '../../core/utils';
-
-// test for hrefs that start with # or /# (for angular)
-const isInternalLinkRegex = /^\/?#[^/!]/;
+import isCurrentPageLink from './is-current-page-link';
 
 /**
- * Determines if element is a skip link
+ * Determines if element is a skip link.
+ *
+ * Define a skip link as any anchor element whose resolved href
+ * resolves to the current page and uses a fragment identifier (#)
+ * and which precedes the first anchor element whose resolved href
+ * does not resolve to the current page or that doesn't use a
+ * fragment identifier.
  * @method isSkipLink
  * @memberof axe.commons.dom
  * @instance
  * @param  {Element} element
  * @return {Boolean}
  */
-function isSkipLink(element) {
-  if (!isInternalLinkRegex.test(element.getAttribute('href'))) {
+export default function isSkipLink(element) {
+  if (!element.href) {
     return false;
   }
 
   let firstPageLink;
   if (typeof cache.get('firstPageLink') !== 'undefined') {
     firstPageLink = cache.get('firstPageLink');
   } else {
-    // define a skip link as any anchor element whose href starts with `#...`
-    // and which precedes the first anchor element whose href doesn't start
-    // with  `#...` (that is, a link to a page)
-    firstPageLink = querySelectorAll(
-      // TODO: es-module-_tree
-      axe._tree,
-      'a:not([href^="#"]):not([href^="/#"]):not([href^="javascript"])'
-    )[0];
+    // jsdom can have window.location.origin set to null
+    if (!window.location.origin) {
+      firstPageLink = querySelectorAll(
+        // TODO: es-module-_tree
+        axe._tree,
+        'a:not([href^="#"]):not([href^="/#"]):not([href^="javascript:"])'
+      )[0];
+    } else {
+      firstPageLink = querySelectorAll(
+        axe._tree,
+        'a[href]:not([href^="javascript:"])'
+      ).find(link => !isCurrentPageLink(link.actualNode));
+    }
 
     // null will signify no first page link
     cache.set('firstPageLink', firstPageLink || null);
@@ -45,5 +54,3 @@ function isSkipLink(element) {
     element.DOCUMENT_POSITION_FOLLOWING
   );
 }
-
-export default isSkipLink;

test/commons/dom/get-element-by-reference.js

@@ -31,6 +31,28 @@ describe('dom.getElementByReference', function() {
     assert.isNull(result);
   });
 
+  it('should return node if target is found (href)', function() {
+    fixture.innerHTML =
+      '<a id="link" href="#target">Hi</a>' + '<a id="target"></a>';
+
+    var node = document.getElementById('link'),
+      expected = document.getElementById('target'),
+      result = axe.commons.dom.getElementByReference(node, 'href');
+
+    assert.equal(result, expected);
+  });
+
+  it('should return node if target is found (usemap)', function() {
+    fixture.innerHTML =
+      '<img id="link" usemap="#target">Hi</a>' + '<map id="target"></map>';
+
+    var node = document.getElementById('link'),
+      expected = document.getElementById('target'),
+      result = axe.commons.dom.getElementByReference(node, 'usemap');
+
+    assert.equal(result, expected);
+  });
+
   it('should prioritize ID', function() {
     fixture.innerHTML =
       '<a id="link" href="#target">Hi</a>' +
@@ -81,4 +103,21 @@ describe('dom.getElementByReference', function() {
 
     assert.equal(result, expected);
   });
+
+  it('should work with absolute links', function() {
+    var currentPage = window.location.origin + window.location.pathname;
+
+    fixture.innerHTML =
+      '<a id="link" href="' +
+      currentPage +
+      '#target">Hi</a>' +
+      '<a id="target"></a>' +
+      '<a name="target"></a>';
+
+    var node = document.getElementById('link'),
+      expected = document.getElementById('target'),
+      result = axe.commons.dom.getElementByReference(node, 'href');
+
+    assert.equal(result, expected);
+  });
 });

test/commons/dom/is-current-page-link.js

@@ -0,0 +1,66 @@
+describe('is-current-page-link', function() {
+  var isCurrentPageLink = axe.commons.dom.isCurrentPageLink;
+  var currentPage = window.location.origin + window.location.pathname;
+  var base;
+
+  afterEach(function() {
+    if (base) {
+      document.head.removeChild(base);
+    }
+  });
+
+  it('should return true for hash links', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '#main';
+    document.body.appendChild(anchor);
+    assert.isTrue(isCurrentPageLink(anchor));
+  });
+
+  it('should return true for relative links to the same page', function() {
+    var anchor = document.createElement('a');
+    anchor.href = window.location.pathname;
+    assert.isTrue(isCurrentPageLink(anchor));
+  });
+
+  it('should return true for absolute links to the same page', function() {
+    var anchor = document.createElement('a');
+    anchor.href = currentPage;
+    assert.isTrue(isCurrentPageLink(anchor));
+  });
+
+  it('should return true for angular skip links', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '/#main';
+    assert.isTrue(isCurrentPageLink(anchor));
+  });
+
+  it('should return false for just "#"', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '#';
+    assert.isFalse(isCurrentPageLink(anchor));
+  });
+
+  it('should return false for relative links to a different page', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '/foo/bar/index.html';
+    assert.isFalse(isCurrentPageLink(anchor));
+  });
+
+  it('should return false for absolute links to a different page', function() {
+    var anchor = document.createElement('a');
+    anchor.href = 'https://my-page.com/foo/bar/index.html';
+    assert.isFalse(isCurrentPageLink(anchor));
+  });
+
+  it('should return false for angular router links (#!)', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '#!main';
+    assert.isFalse(isCurrentPageLink(anchor));
+  });
+
+  it('should return false for angular router links (#/)', function() {
+    var anchor = document.createElement('a');
+    anchor.href = '#/main';
+    assert.isFalse(isCurrentPageLink(anchor));
+  });
+});

test/commons/dom/is-skip-link.js

@@ -2,9 +2,14 @@ describe('dom.isSkipLink', function() {
   'use strict';
 
   var fixture = document.getElementById('fixture');
+  var baseEl;
 
   afterEach(function() {
     fixture.innerHTML = '';
+
+    if (baseEl) {
+      baseEl.parentNode.removeChild(baseEl);
+    }
   });
 
   it('should return true if the href points to an ID', function() {
@@ -35,6 +40,20 @@ describe('dom.isSkipLink', function() {
     assert.isTrue(axe.commons.dom.isSkipLink(node));
   });
 
+  it('should return false if the URI is angular #!', function() {
+    fixture.innerHTML = '<a href="#!target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isFalse(axe.commons.dom.isSkipLink(node));
+  });
+
+  it('should return false if the URI is angular #/', function() {
+    fixture.innerHTML = '<a href="#/target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isFalse(axe.commons.dom.isSkipLink(node));
+  });
+
   it('should return true for multiple skip-links', function() {
     fixture.innerHTML =
       '<a id="skip-link1" href="#target1">Click Here></a><a id="skip-link2" href="/#target2">Click Here></a><a id="skip-link3" href="#target3">Click Here></a>';
@@ -68,4 +87,41 @@ describe('dom.isSkipLink', function() {
     var node = fixture.querySelector('#skip-link');
     assert.isTrue(axe.commons.dom.isSkipLink(node));
   });
+
+  it('should return true for hash href that resolves to current page', function() {
+    fixture.innerHTML =
+      '<a href="' + window.location.pathname + '#target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isTrue(axe.commons.dom.isSkipLink(node));
+  });
+
+  it('should return true for absolute path hash href', function() {
+    var url = window.location.href;
+    fixture.innerHTML = '<a href="' + url + '#target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isTrue(axe.commons.dom.isSkipLink(node));
+  });
+
+  it('should return false for absolute path href that points to another document', function() {
+    var origin = window.location.origin;
+    fixture.innerHTML =
+      '<a href="' + origin + '/something.html#target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isFalse(axe.commons.dom.isSkipLink(node));
+  });
+
+  it('should return false for href with <base> tag that points to another document', function() {
+    baseEl = document.createElement('base');
+    baseEl.href = 'https://www.google.com/';
+    document.getElementsByTagName('head')[0].appendChild(baseEl);
+
+    fixture.innerHTML =
+      '<a href="' + window.location.pathname + '#target">Click Here</a>';
+    axe._tree = axe.utils.getFlattenedTree(fixture);
+    var node = fixture.querySelector('a');
+    assert.isFalse(axe.commons.dom.isSkipLink(node));
+  });
 });