commit b426fafff6238dda8d86fa668f585cba732dd272
Author: Jonathan Hamilton <jtrhamilton@gmail.com>
Date:   Mon Jun 1 13:33:59 2015 -0700

    Fix some Node::operator[] regressions from 0.5.1
    
    "const Node Node::operator[](const Key& key) const" changed from
    returning new empty node if the key was missing in 0.5.1 to returning
    a shared 'zombie' node in 0.5.2 to resolve a memory leak.
    
    (Specifically 1025f76df1b32b6ec3571ca928d7797a768a3341 was where this
    was introduced)
    
    This caused some regressions where this 'zombie' object threw exceptions
    in some functions where the 'empty' object would not.
    
    This change fixes the Node::as(fallback) method (to return the
    'fallback' instead of throwing an exception) and the
    Node::begin()/Node::end() methods to return default-constructed
    iterators (so begin() == end() in such cases) instead of another
    exception.

--- include/yaml-cpp/node/impl.h.orig
+++ include/yaml-cpp/node/impl.h
@@ -149,7 +149,7 @@ inline const T Node::as() const {
 template <typename T, typename S>
 inline const T Node::as(const S& fallback) const {
   if (!m_isValid)
-    throw InvalidNode();
+    return fallback;
   return as_if<T, S>(*this)(fallback);
 }
 
@@ -282,26 +282,26 @@ inline std::size_t Node::size() const {
 
 inline const_iterator Node::begin() const {
   if (!m_isValid)
-    throw InvalidNode();
+    return const_iterator();
   return m_pNode ? const_iterator(m_pNode->begin(), m_pMemory)
                  : const_iterator();
 }
 
 inline iterator Node::begin() {
   if (!m_isValid)
-    throw InvalidNode();
+    return iterator();
   return m_pNode ? iterator(m_pNode->begin(), m_pMemory) : iterator();
 }
 
 inline const_iterator Node::end() const {
   if (!m_isValid)
-    throw InvalidNode();
+    return const_iterator();
   return m_pNode ? const_iterator(m_pNode->end(), m_pMemory) : const_iterator();
 }
 
 inline iterator Node::end() {
   if (!m_isValid)
-    throw InvalidNode();
+    return iterator();
   return m_pNode ? iterator(m_pNode->end(), m_pMemory) : iterator();
 }
 
--- test/node/node_test.cpp.orig
+++ test/node/node_test.cpp
@@ -80,6 +80,12 @@ TEST(NodeTest, MapWithUndefinedValues) {
   EXPECT_EQ(2, node.size());
 }
 
+TEST(NodeTest, UndefinedConstNodeWithFallback) {
+  Node node;
+  const Node& cn = node;
+  EXPECT_EQ(cn["undefined"].as<int>(3), 3);
+}
+
 TEST(NodeTest, MapIteratorWithUndefinedValues) {
   Node node;
   node["key"] = "value";
@@ -91,6 +97,32 @@ TEST(NodeTest, MapIteratorWithUndefinedValues) {
   EXPECT_EQ(1, count);
 }
 
+TEST(NodeTest, ConstIteratorOnConstUndefinedNode) {
+  Node node;
+  const Node& cn = node;
+  const Node& undefinedCn = cn["undefined"];
+
+  std::size_t count = 0;
+  for (const_iterator it = undefinedCn.begin(); it != undefinedCn.end(); ++it) {
+    count++;
+ }
+  EXPECT_EQ(0, count);
+}
+
+TEST(NodeTest, IteratorOnConstUndefinedNode) {
+  Node node;
+  const Node& cn = node;
+  const Node& undefinedCn = cn["undefined"];
+
+  Node& nonConstUndefinedNode = const_cast<Node&>(undefinedCn);
+
+  std::size_t count = 0;
+  for (iterator it = nonConstUndefinedNode.begin(); it != nonConstUndefinedNode.end(); ++it) {
+    count++;
+  }
+  EXPECT_EQ(0, count);
+}
+
 TEST(NodeTest, SimpleSubkeys) {
   Node node;
   node["device"]["udid"] = "12345";