priority: initialize children of exclusive

Don't forget to set `parent` property of children when inserting
exclusive node.

Fix: spdy-http2/node-spdy#244

lib/spdy-transport/priority.js

@@ -48,6 +48,7 @@ PriorityNode.prototype.getPriorityRange = function getPriorityRange() {
 };
 
 PriorityNode.prototype.addChild = function addChild(child) {
+  child.parent = this;
   utils.binaryInsert(this.children.list, child, compareChildren);
   this.children.weight += child.weight;
 
@@ -128,9 +129,11 @@ PriorityTree.prototype.add = function add(options) {
   if (parent === undefined)
     return this.addDefault(options.id);
 
-  debug('add node=%d parent=%d',
+  debug('add node=%d parent=%d weight=%d exclusive=%d',
         options.id,
-        options.parent === null ? -1 : options.parent);
+        options.parent === null ? -1 : options.parent,
+        options.weight || this.defaultWeight,
+        options.exclusive ? 1 : 0);
 
   var children;
   if (options.exclusive)
@@ -149,8 +152,10 @@ PriorityTree.prototype.add = function add(options) {
   }
 
   this.count++;
-  if (this.count > this.maxCount)
+  if (this.count > this.maxCount) {
+    debug('hit maximum remove id=%d', this.list[0].id);
     this.list.shift().remove();
+  }
 
   // Root node is not subject to removal
   if (node.parent !== null)

test/base/priority-test.js

@@ -132,6 +132,11 @@ describe('Stream Priority tree', function() {
     assert.deepEqual([ 2, 3, 4, 5, 6 ].map(function(id) {
       return tree.get(id).priority;
     }), [ 0.5, 0.25, 0.125, 0.125, 0.5 ]);
+
+    // This should not throw when removing ex-child of node swapped by
+    // exclusive one
+    tree.add({ id: 7, parent: 5, exclusive: false, weight: 2 });
+    tree.add({ id: 8, parent: 5, exclusive: false, weight: 2 });
   });
 
   it('should use default weight', function() {