Fixes #3308. Use an explicit undefined check to test if logical tree information exists.

src/lib/dom-tree-api.html

@@ -82,28 +82,39 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       return node.__dom.childNodes;
     },
 
+    // NOTE: __dom can be created under 2 conditions: (1) an element has a
+    // logical tree, or (2) an element is in a logical tree. In case (1), the
+    // element will store firstChild/lastChild, and in case (2), the element
+    // will store parentNode, nextSibling, previousSibling. This means that
+    // the mere existence of __dom is not enough to know if the requested
+    // logical data is available and instead we do an explicit undefined check.
     getParentNode: function(node) {
-      return node.__dom && node.__dom.parentNode || node.parentNode;
+      return node.__dom && node.__dom.parentNode !== undefined ? 
+        node.__dom.parentNode : node.parentNode;
     },
 
     getFirstChild: function(node) {
-      return node.__dom && node.__dom.firstChild || node.firstChild;
+      return node.__dom && node.__dom.firstChild !== undefined ? 
+        node.__dom.firstChild : node.firstChild;
     },
 
     getLastChild: function(node) {
-      return node.__dom && node.__dom.lastChild || node.lastChild;
+      return node.__dom && node.__dom.lastChild  !== undefined ? 
+        node.__dom.lastChild : node.lastChild;
     },
 
     getNextSibling: function(node) {
-      return node.__dom && node.__dom.nextSibling || node.nextSibling;
+      return node.__dom && node.__dom.nextSibling  !== undefined ? 
+        node.__dom.nextSibling : node.nextSibling;
     },
 
     getPreviousSibling: function(node) {
-      return node.__dom && node.__dom.previousSibling || node.previousSibling;
+      return node.__dom && node.__dom.previousSibling  !== undefined ? 
+        node.__dom.previousSibling : node.previousSibling;
     },
 
     getFirstElementChild: function(node) {
-      return node.__dom && node.__dom.firstChild ? 
+      return node.__dom && node.__dom.firstChild !== undefined ?  
         this._getFirstElementChild(node) : node.firstElementChild;
     },
 
@@ -116,8 +127,8 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
     },
 
     getLastElementChild: function(node) {
-      return node.__dom && node.__dom.lastChild ? 
-        this._getLastElementChild(node) : node.firstElementChild;
+      return node.__dom && node.__dom.lastChild !== undefined ?
+        this._getLastElementChild(node) : node.lastElementChild;
     },
 
     _getLastElementChild: function(node) {
@@ -129,7 +140,7 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
     },
 
     getNextElementSibling: function(node) {
-      return node.__dom && node.__dom.nextSibling ? 
+      return node.__dom && node.__dom.nextSibling !== undefined ?
         this._getNextElementSibling(node) : node.nextElementSibling;
     },
 
@@ -142,7 +153,7 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
     },
 
     getPreviousElementSibling: function(node) {
-      return node.__dom && node.__dom.previousSibling ? 
+      return node.__dom && node.__dom.previousSibling !== undefined ?
         this._getPreviousElementSibling(node) : node.previousElementSibling;
     },
 
@@ -241,8 +252,11 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       if (n) {
         n.__dom.previousSibling = p;
       }
+      // When an element is removed, logical data is no longer tracked.
+      // Explicitly set `undefined` here to indicate this. This is disginguished
+      // from `null` which is set if info is null.
       node.__dom.parentNode = node.__dom.previousSibling = 
-        node.__dom.nextSibling = null;
+        node.__dom.nextSibling = undefined;
       // remove caching of childNodes
       container.__dom.childNodes = null;
     }

test/unit/polymer-dom-elements.html

@@ -126,6 +126,11 @@
   <script>Polymer({is: 'x-echo'});</script>
 </dom-module>
 
+<dom-module id="x-simple">
+  <template><div>simple</div></template>
+  <script>Polymer({is: 'x-simple'});</script>
+</dom-module>
+
 
 <dom-module id="x-redistribute-a-b">
   <template>

test/unit/polymer-dom.js

@@ -755,6 +755,36 @@ suite('Polymer.dom accessors', function() {
     assert.equal(Polymer.dom(child).previousElementSibling, before, 'previousElementSibling incorrect');
   });
 
+  test('Polymer.dom node accessors (empty logical tree)', function() {
+    var element = document.createElement('x-simple');
+    assert.equal(Polymer.dom(element).parentNode, null, 'parentNode incorrect');
+    assert.equal(Polymer.dom(element).firstChild, null, 'firstChild incorrect');
+    assert.equal(Polymer.dom(element).lastChild, null, 'lastChild incorrect');
+    assert.equal(Polymer.dom(element).nextSibling, null, 'nextSibling incorrect');
+    assert.equal(Polymer.dom(element).previousSibling, null, 'previousSibling incorrect');
+    assert.equal(Polymer.dom(element).firstElementChild, null, 'firstElementChild incorrect');
+    assert.equal(Polymer.dom(element).lastElementChild, null, 'lastElementChild incorrect');
+    assert.equal(Polymer.dom(element).nextElementSibling, null, 'nextElementSibling incorrect');
+    assert.equal(Polymer.dom(element).previousElementSibling, null, 'previousElementSibling incorrect');
+  });
+
+  test('Polymer.dom node accessors (unmanaged logical tree)', function() {
+    var element = document.createElement('div');
+    var child1 = document.createElement('div');
+    var child2 = document.createElement('div');
+    element.appendChild(child1);
+    element.appendChild(child2);
+    assert.equal(Polymer.dom(element).parentNode, null, 'parentNode incorrect');
+    assert.equal(Polymer.dom(element).firstChild, child1, 'firstChild incorrect');
+    assert.equal(Polymer.dom(element).lastChild, child2, 'lastChild incorrect');
+    assert.equal(Polymer.dom(element).nextSibling, null, 'nextSibling incorrect');
+    assert.equal(Polymer.dom(element).previousSibling, null, 'previousSibling incorrect');
+    assert.equal(Polymer.dom(element).firstElementChild, child1, 'firstElementChild incorrect');
+    assert.equal(Polymer.dom(element).lastElementChild, child2, 'lastElementChild incorrect');
+    assert.equal(Polymer.dom(element).nextElementSibling, null, 'nextElementSibling incorrect');
+    assert.equal(Polymer.dom(element).previousElementSibling, null, 'previousElementSibling incorrect');
+  });
+
   test('Polymer.dom textContent', function() {
     var testElement = document.createElement('x-project');
     Polymer.dom(testElement).textContent = 'Hello World';