Bug 1409040 - Make element.isXULElement more resiliant. r=maja_zf

Fixes isXULElement to recognise XBL elements, such as <xbl:framebox>.

Also tightens up the input checks so that arbitrary objects can be
tested, as checking node.namespaceURI directly could cause a JS error
if node is not an object.  Before checking the namespace we also ensure
it's an element node so that text- and comment nodes are not picked up.

This patch also introduces tests, which were sorely missing.

MozReview-Commit-ID: 8LNF1z3X1gP

--HG--
extra : rebase_source : ffacc5b1336b35624aaf0534101ce5c3fbdeaa95

testing/marionette/element.js

@@ -19,6 +19,7 @@ const {PollPromise} = Cu.import("chrome://marionette/content/sync.js", {});
 
 this.EXPORTED_SYMBOLS = ["element"];
 
+const XBLNS = "http://www.mozilla.org/xbl";
 const XMLNS = "http://www.w3.org/1999/xhtml";
 const XULNS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
@@ -1050,8 +1051,21 @@ element.scrollIntoView = function(el) {
   }
 };
 
-element.isXULElement = function(el) {
-  return el.namespaceURI === XULNS;
+/**
+ * Ascertains whether <var>el</var> is a XUL- or XBL element.
+ *
+ * @param {*} node
+ *     Element thought to be a XUL- or XBL element.
+ *
+ * @return {boolean}
+ *     True if <var>node</var> is a XULElement or XBLElement,
+ *     false otherwise.
+ */
+element.isXULElement = function(node) {
+  return typeof node == "object" &&
+      node !== null &&
+      node.nodeType === node.ELEMENT_NODE &&
+      [XBLNS, XULNS].includes(node.namespaceURI);
 };
 
 const boolEls = {

testing/marionette/test_element.js

@@ -6,7 +6,10 @@ const {utils: Cu} = Components;
 
 Cu.import("chrome://marionette/content/element.js");
 
-class DOMElement {
+const XBLNS = "http://www.mozilla.org/xbl";
+const XULNS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+
+class Element {
   constructor(tagName, attrs = {}) {
     this.tagName = tagName;
     this.localName = tagName;
@@ -14,6 +17,15 @@ class DOMElement {
     for (let attr in attrs) {
       this[attr] = attrs[attr];
     }
+  }
+
+  get nodeType() { return 1; }
+  get ELEMENT_NODE() { return 1; }
+}
+
+class DOMElement extends Element {
+  constructor(tagName, attrs = {}) {
+    super(tagName, attrs);
 
     if (this.localName == "option") {
       this.selected = false;
@@ -24,9 +36,6 @@ class DOMElement {
     }
   }
 
-  get nodeType() { return 1; }
-  get ELEMENT_NODE() { return 1; }
-
   getBoundingClientRect() {
     return {
       top: 0,
@@ -35,9 +44,25 @@ class DOMElement {
       height: 100,
     };
   }
-};
+}
+
+class XULElement extends Element {
+  constructor(tagName, attrs = {}) {
+    super(tagName, attrs);
+    this.namespaceURI = XULNS;
+  }
+}
+
+class XBLElement extends XULElement {
+  constructor(tagName, attrs = {}) {
+    super(tagName, attrs);
+    this.namespaceURI = XBLNS;
+  }
+}
 
 const domEl = new DOMElement("p");
+const xulEl = new XULElement("browser");
+const xblEl = new XBLElement("framebox");
 
 add_test(function test_isSelected() {
   let checkbox = new DOMElement("input", {type: "checkbox"});
@@ -68,6 +93,16 @@ add_test(function test_isSelected() {
   run_next_test();
 });
 
+add_test(function test_isXULElement() {
+  ok(element.isXULElement(xulEl));
+  ok(element.isXULElement(xblEl));
+  for (let typ of [true, 42, {}, [], undefined, null]) {
+    ok(!element.isXULElement(typ));
+  }
+
+  run_next_test();
+});
+
 add_test(function test_coordinates() {
   let p = element.coordinates(domEl);
   ok(p.hasOwnProperty("x"));