fix rosmsg show from bag

tools/rosmsg/package.xml

@@ -21,6 +21,7 @@
 
   <run_depend version_gte="0.6.4">catkin</run_depend>
   <run_depend>genmsg</run_depend>
+  <run_depend version_gte="0.6.5">genpy</run_depend>
   <run_depend>python-rospkg</run_depend>
   <run_depend>rosbag</run_depend>
   <run_depend>roslib</run_depend>

tools/rosmsg/src/rosmsg/__init__.py

@@ -48,6 +48,7 @@
 
 import rospkg
 import genmsg
+from genpy.dynamic import generate_dynamic
 
 import roslib.message
 import rosbag
@@ -596,17 +597,24 @@ def rosmsg_cmd_show(mode, full, alias='show'):
         parser.error(cmd+" does not understand C++-style namespaces (i.e. '::').\nPlease refer to msg/srv types as 'package_name/Type'.")
     elif '.' in arg:
         parser.error("invalid message type '%s'.\nPlease refer to msg/srv types as 'package_name/Type'." % arg)
+    rospack = rospkg.RosPack()
     if options.bag:
         bag_file = options.bag
         if not os.path.exists(bag_file):
             raise ROSMsgException("ERROR: bag file [%s] does not exist"%bag_file)
         for topic, msg, t in rosbag.Bag(bag_file).read_messages(raw=True):
             datatype, _, _, _, pytype = msg
             if datatype == arg:
-                print(get_msg_text(datatype, options.raw, pytype._full_text))
+                if options.raw:
+                    print(pytype._full_text)
+                else:
+                    context = genmsg.MsgContext.create_default()
+                    msgs = generate_dynamic(datatype, pytype._full_text)
+                    for t, msg in msgs.items():
+                        context.register(t, msg._spec)
+                    print(spec_to_str(context, msgs[datatype]._spec))
                 break
     else:
-        rospack = rospkg.RosPack()
         if '/' in arg: #package specified
             rosmsg_debug(rospack, mode, arg, options.raw)
         else: