Handle null-values properly

lib/mysql/parser.js

@@ -493,6 +493,16 @@ Parser.prototype.write = function(buffer) {
         }
 
         packet.columnLength = lengthCoded(packet.columnLength);
+        if (!packet.columnLength) {
+          packet.emit('data', new Buffer(0), 0);
+          if (packet.received < packet.length) {
+            advance(Parser.COLUMN_VALUE_LENGTH);
+          } else {
+            self.packet = packet = null;
+            self.state = state = Parser.PACKET_LENGTH;
+            continue;
+          }
+        }
         break;
       case Parser.COLUMN_VALUE_STRING:
         var remaining = packet.columnLength - packet.index, read;

lib/mysql/query.js

@@ -53,7 +53,11 @@ Query.prototype._handlePacket = function(packet) {
       row[field] = '';
 
       packet.on('data', function(buffer, remaining) {
-        row[field] += buffer;
+        if (buffer.length) {
+          row[field] += buffer;
+        } else {
+          row[field] = null;
+        }
 
         if (remaining == 0) {
           self._rowIndex++;

test/system/test-client-query-null.js

@@ -0,0 +1,17 @@
+require('../common');
+var Client = require('mysql').Client,
+    client = Client(TEST_CONFIG),
+    gently = new Gently();
+
+// our test db might not exist yet, so don't try to connect to it
+client.database = '';
+client.connect();
+
+client.query('SELECT NULL as field_a, NULL as field_b', function(err, results) {
+  if (err) throw err;
+
+  assert.strictEqual(results[0].field_a, null);
+  assert.strictEqual(results[0].field_b, null);
+  client.end();
+});
+