Tolerate preProcessNode callbacks that remove nodes entirely (supplyi…

…ng an empty array of replacements)

spec/bindingAttributeBehaviors.js

@@ -484,11 +484,22 @@ describe('Binding attribute syntax', function() {
                 return newNodes;
             }
 
+            // Example: Remove any <button> elements
+            if (node.tagName && node.tagName.toLowerCase() === "button") {
+                node.parentNode.removeChild(node);
+                return []; // Replace with empty array
+            }
+
             // Example: Leave the node unchanged.
             return null;
         };
 
-        testNode.innerHTML = "<prop1></prop1>, <p data-bind='text: prop2'></p>, prefix {{ prop3 }} suffix<div data-bind='foreach: prop4'> {{ prop3 }} x</div>";
+        testNode.innerHTML = "<prop1></prop1>, "
+                           + "<p data-bind='text: prop2'></p>, "
+                           + "prefix {{ prop3 }} suffix"
+                           + "<div data-bind='foreach: prop4'>"
+                           +     "<button>DeleteMe</button> {{ prop3 }} x<button>DeleteMe</button>"
+                           + "</div>";
         var vm = {
             prop1: 'PROP1VAL',
             prop2: 'PROP2VAL',

src/templating/templating.js

@@ -10,7 +10,7 @@
         var node, nextInQueue = firstNode, firstOutOfRangeNode = ko.virtualElements.nextSibling(lastNode);
         while (nextInQueue && ((node = nextInQueue) !== firstOutOfRangeNode)) {
             nextInQueue = ko.virtualElements.nextSibling(node);
-            action(node);
+            action(node, nextInQueue);
         }
     }
 
@@ -28,15 +28,28 @@
                 preProcessNode = provider['preProcessNode'];
 
             if (preProcessNode) {
-                invokeForEachNodeInContinuousRange(firstNode, lastNode, function(node) {
+                // Because preProcessNodes can remove nodes, it's tricky to work out what is the last node in the
+                // continuous array after preprocessing. We need the last node from the last nonempty set of replacement
+                // nodes. To find it, lastNodeSeenDuringPreProcessing tracks the last such candidate we've seen.
+                var lastNodeSeenDuringPreProcessing = null;
+
+                invokeForEachNodeInContinuousRange(firstNode, lastNode, function(node, nextNodeInRange) {
                     var newNodes = preProcessNode.call(provider, node);
                     if (newNodes) {
                         if (node === firstNode)
-                            firstNode = newNodes[0];
-                        if (node === lastNode)
-                            lastNode = newNodes[newNodes.length-1];
+                            firstNode = newNodes[0] || nextNodeInRange;
+                        lastNodeSeenDuringPreProcessing = newNodes[newNodes.length-1] || lastNodeSeenDuringPreProcessing;
+                    } else {
+                        lastNodeSeenDuringPreProcessing = node;
                     }
                 });
+                lastNode = lastNodeSeenDuringPreProcessing;
+
+                // preProcessNode might have removed all the nodes, in which case there's nothing left to activate bindings on
+                if (!firstNode) { // Note that lastNode can only be null if firstNode is, so no need to check for that
+                    return;
+                }
+
                 // Because preProcessNode can change the nodes, including the first and last nodes, replace
                 // continuousNodeArray with the latest first/last nodes (we don't actually need the inner nodes)
                 continuousNodeArray.length = 0;