add topic pub prototype completer

Signed-off-by: artivis <jeremie.deray@canonical.com>

ros2topic/ros2topic/api/__init__.py

@@ -23,6 +23,10 @@
 from rclpy.validate_full_topic_name import validate_full_topic_name
 from ros2cli.node.strategy import NodeStrategy
 from ros2msg.api import message_type_completer
+from rosidl_parser.definition import AbstractNestedType
+from rosidl_parser.definition import NamespacedType
+from rosidl_runtime_py.convert import message_to_yaml
+from rosidl_runtime_py.import_message import import_message_from_namespaced_type
 
 
 def get_topic_names_and_types(*, node, include_hidden_topics=False):
@@ -137,3 +141,23 @@ def _get_msg_class(node, topic, include_hidden_topics):
         return None
 
     return import_message_type(topic, message_type)
+
+
+class TopicMessagePrototypeCompleter:
+    """Callable returning a message prototype."""
+
+    def __init__(self, *, topic_type_key=None):
+        self.topic_type_key = topic_type_key
+
+    def __call__(self, prefix, parsed_args, **kwargs):
+        topic_type = getattr(parsed_args, self.topic_type_key)
+        try:
+            parts = topic_type.split('/')
+            package_name = parts[0]
+            interface_type = parts[1]
+            message_type = parts[-1]
+        except LookupError as e:
+            return None
+        message = import_message_from_namespaced_type(
+            AbstractNestedType(NamespacedType([package_name, interface_type], message_type)))
+        return [message_to_yaml(message())]

ros2topic/ros2topic/verb/pub.py

@@ -19,6 +19,7 @@
 from ros2topic.api import import_message_type
 from ros2topic.api import TopicNameCompleter
 from ros2topic.api import TopicTypeCompleter
+from ros2topic.api import TopicMessagePrototypeCompleter
 from ros2topic.verb import VerbExtension
 from rosidl_runtime_py import set_message_fields
 import yaml
@@ -38,11 +39,13 @@ def add_arguments(self, parser, cli_name):
             help="Type of the ROS message (e.g. 'std_msgs/String')")
         arg.completer = TopicTypeCompleter(
             topic_name_key='topic_name')
-        parser.add_argument(
+        arg = parser.add_argument(
             'values', nargs='?', default='{}',
             help='Values to fill the message with in YAML format '
                  '(e.g. "data: Hello World"), '
                  'otherwise the message will be published with default values')
+        arg.completer = TopicMessagePrototypeCompleter(
+            topic_type_key='message_type')
         parser.add_argument(
             '-r', '--rate', metavar='N', type=float, default=1.0,
             help='Publishing rate in Hz (default: 1)')