Fix namespacing for multiple instances of gazebo_ros2_control plugin

doc/index.rst

@@ -218,6 +218,38 @@ The following is a basic configuration of the controllers:
 .. literalinclude:: ../gazebo_ros2_control_demos/config/cart_controller.yaml
    :language: yaml
 
+
+Multiple Namespaces
+-----------------------------------------------------------
+The gazebo_ros2_control plugin can be launched in multiple namespaces. This is useful if it is desired to have multiple robots of the same description running at the same time.
+If the namespace is to be defined in the URDF file, then you can use the ``<namespace>`` tag as detailed below:
+
+.. code-block:: xml
+
+  <gazebo>
+    <plugin name="gazebo_ros2_control" filename="libgazebo_ros2_control.so">
+      <parameters> $(arg control_yaml) </parameters>
+      <ros>
+        <namespace>r1</namespace>
+        <remapping>/tf:=tf</remapping>
+        <remapping>/tf_static:=tf_static</remapping>
+        <remapping>diffdrive_controller/odom:=odom</remapping>
+      </ros>
+    </plugin>
+  </gazebo>
+
+Where ``r1`` is the namespace that the plugin nodes will be run in. Please note that the remapping of ``/tf`` and ``/tf_static`` is recommended only if you want to have a separate TF buffer for each namespace, e.g ``/r1/tf``
+
+A second method for launching in namespaces is by using the Gazebo ``spawn_entity.py`` tool and setting the ``-robot_namespace`` parameter to the script:
+
+.. code-block:: bash
+
+  ros2 run gazebo_ros spawn_entity.py -entity robot_1 -robot_namespace r1 -topic robot_description
+
+The script calls the ``spawn_entity`` service to spawn an entity named ``robot_1`` in the namespace ``r1``.  It is assumed that a robot description is being published by a ``robot_state_publisher`` node on the topic ``robot_description``, this will also be used for the ``gazebo_ros2_control`` plugin.
+
+The ``spawn_entity.py`` script will rewrite the robot description to include a namespace for every plugin tag. Please note that this method will apply a namespace to every plugin in the robot description. It will also overwrite any existing namespaces set in the description file.
+
 gazebo_ros2_control_demos
 ==========================================
 

gazebo_ros2_control/src/gazebo_ros2_control_plugin.cpp

@@ -233,24 +233,10 @@ void GazeboRosControlPlugin::Load(gazebo::physics::ModelPtr parent, sdf::Element
 
   if (sdf->HasElement("ros")) {
     sdf = sdf->GetElement("ros");
-
-    // Set namespace if tag is present
-    if (sdf->HasElement("namespace")) {
-      std::string ns = sdf->GetElement("namespace")->Get<std::string>();
-      // prevent exception: namespace must be absolute, it must lead with a '/'
-      if (ns.empty() || ns[0] != '/') {
-        ns = '/' + ns;
-      }
-      std::string ns_arg = std::string("__ns:=") + ns;
-      arguments.push_back(RCL_REMAP_FLAG);
-      arguments.push_back(ns_arg);
-    }
-
     // Get list of remapping rules from SDF
     if (sdf->HasElement("remapping")) {
       sdf::ElementPtr argument_sdf = sdf->GetElement("remapping");
 
-      arguments.push_back(RCL_ROS_ARGS_FLAG);
       while (argument_sdf) {
         std::string argument = argument_sdf->Get<std::string>();
         arguments.push_back(RCL_REMAP_FLAG);