feat: Add dom.getComposedParent function

lib/commons/dom/find-up.js

@@ -22,11 +22,8 @@ dom.findUp = function (element, target) {
 		return null;
 	}
 
-	parent = (element.assignedSlot) ? element.assignedSlot : element.parentNode;
-	if (parent.nodeType === 11) {
-		parent = parent.host;
-	}
 	// recursively walk up the DOM, checking each parent node
+	parent = dom.getComposedParent(element);
 	while (parent && matches.indexOf(parent) === -1) {
 		parent = (parent.assignedSlot) ? parent.assignedSlot : parent.parentNode;
 		if (parent && parent.nodeType === 11) {

lib/commons/dom/get-composed-parent.js

@@ -0,0 +1,19 @@
+/*global dom */
+/**
+ * Get an element's parent in the composed tree
+ * @param   DOMNode   Element
+ * @return  DOMNode   Parent element
+ */
+dom.getComposedParent = function getComposedParent (element)  {
+  if (element.assignedSlot) {
+    return element.assignedSlot; // content of a shadow DOM slot
+  } else if (element.parentNode) {
+    var parentNode = element.parentNode;
+    if (parentNode.nodeType === 1) {
+      return parentNode; // Regular node
+    } else if (parentNode.host) {
+      return parentNode.host; // Shadow root
+    }
+  }
+  return null; // Root node
+};

lib/commons/dom/is-visible.js

@@ -64,8 +64,7 @@ dom.isVisible = function (el, screenReader, recursed) {
 		return false;
 	}
 
-	parent = (el.assignedSlot) ? el.assignedSlot : el.parentNode;
-
+	parent = dom.getComposedParent(el);
 	if (parent) {
 		return dom.isVisible(parent, screenReader, true);
 	}

test/commons/dom/get-composed-parent.js

@@ -0,0 +1,72 @@
+/* global xit */
+describe('dom.getComposedParent', function () {
+  'use strict';
+  var getComposedParent = axe.commons.dom.getComposedParent;
+  var fixture = document.getElementById('fixture');
+  var shadowSupport = document.body && typeof document.body.attachShadow === 'function';
+
+  afterEach(function () {
+    fixture.innerHTML = '';
+  });
+
+  it('returns the parentNode normally', function () {
+    fixture.innerHTML = '<div id="parent"><div id="target"></div></div>';
+
+    var actual = getComposedParent(document.getElementById('target'));
+    assert.instanceOf(actual, Node);
+    assert.equal(actual, document.getElementById('parent'));
+  });
+
+  it('returns null from the documentElement', function () {
+    assert.isNull(
+      getComposedParent(document.documentElement)
+    );
+  });
+
+  (shadowSupport ? it : xit)('returns the slot node for slotted content', function () {
+    fixture.innerHTML = '<div id="shadow"><div id="target"></div></div>';
+    var shadowRoot = document.getElementById('shadow').attachShadow({ mode: 'open' });
+    shadowRoot.innerHTML = '<div id="grand-parent">' +
+      '<slot id="parent"></slot>' +
+    '</div>';
+
+    var actual = getComposedParent(fixture.querySelector('#target'));
+    assert.instanceOf(actual, Node);
+    assert.equal(actual, shadowRoot.querySelector('#parent'));
+  });
+
+  (shadowSupport ? it : xit)('returns explicitly slotted nodes', function () {
+    fixture.innerHTML = '<div id="shadow"><div id="target" slot="bar"></div></div>';
+    var shadowRoot = document.getElementById('shadow').attachShadow({ mode: 'open' });
+    shadowRoot.innerHTML = '<div id="grand-parent">' +
+      '<slot name="foo"></slot>' +
+      '<slot id="parent" name="bar"></slot>' +
+    '</div>';
+
+    var actual = getComposedParent(fixture.querySelector('#target'));
+    assert.instanceOf(actual, Node);
+    assert.equal(actual, shadowRoot.querySelector('#parent'));
+  });
+
+  (shadowSupport ? it : xit)('returns elements within a shadow tree', function () {
+    fixture.innerHTML = '<div id="shadow"> content </div>';
+    var shadowRoot = document.getElementById('shadow').attachShadow({ mode: 'open' });
+    shadowRoot.innerHTML = '<div id="parent">' +
+      '<slot id="target"></slot>' +
+    '</div>';
+
+    var actual = getComposedParent(shadowRoot.querySelector('#target'));
+    assert.instanceOf(actual, Node);
+    assert.equal(actual, shadowRoot.querySelector('#parent'));
+  });
+
+  (shadowSupport ? it : xit)('returns the host when it reaches the shadow root', function () {
+    fixture.innerHTML = '<div id="parent"> content </div>';
+    var shadowRoot = document.getElementById('parent').attachShadow({ mode: 'open' });
+    shadowRoot.innerHTML = '<div id="target"> <slot></slot> </div>';
+
+    var actual = getComposedParent(shadowRoot.querySelector('#target'));
+    assert.instanceOf(actual, Node);
+    assert.equal(actual, fixture.querySelector('#parent'));
+  });
+});