Merge pull request #144 from Herringway/add-for-empty-node

allow uninitialized nodes to become sequence/mapping nodes
merged-on-behalf-of: BBasile <BBasile@users.noreply.github.com>

source/dyaml/node.d

@@ -1531,6 +1531,10 @@ struct Node
          */
         void add(T)(T value)
         {
+            if (!isValid)
+            {
+                setValue(Node[].init);
+            }
             enforce(isSequence(),
                     new NodeException("Trying to add an element to a " ~ nodeTypeString ~ " node", startMark_));
 
@@ -1546,6 +1550,19 @@ struct Node
                 add(5.0f);
                 assert(opIndex(4).as!float == 5.0f);
             }
+            with(Node())
+            {
+                add(5.0f);
+                assert(opIndex(0).as!float == 5.0f);
+            }
+            with(Node(5.0f))
+            {
+                assertThrown!NodeException(add(5.0f));
+            }
+            with(Node([5.0f : true]))
+            {
+                assertThrown!NodeException(add(5.0f));
+            }
         }
 
         /** Add a key-value pair to a mapping.
@@ -1565,6 +1582,10 @@ struct Node
          */
         void add(K, V)(K key, V value)
         {
+            if (!isValid)
+            {
+                setValue(Node.Pair[].init);
+            }
             enforce(isMapping(),
                     new NodeException("Trying to add a key-value pair to a " ~
                               nodeTypeString ~ " node",
@@ -1581,6 +1602,19 @@ struct Node
                 add(5, "6");
                 assert(opIndex(5).as!string == "6");
             }
+            with(Node())
+            {
+                add(5, "6");
+                assert(opIndex(5).as!string == "6");
+            }
+            with(Node(5.0f))
+            {
+                assertThrown!NodeException(add(5, "6"));
+            }
+            with(Node([5.0f]))
+            {
+                assertThrown!NodeException(add(5, "6"));
+            }
         }
 
         /** Determine whether a key is in a mapping, and access its value.