Basic rocker config to install and enable different rmw layers

Only tested with cyclonedds for the moment.

setup.py

@@ -60,6 +60,7 @@
             'port = rocker.extensions:Port',
             'privileged = rocker.extensions:Privileged',
             'pulse = rocker.extensions:PulseAudio',
+            'rmw = rocker.rmw_extension:RMW',
             'ssh = rocker.ssh_extension:Ssh',
             'user = rocker.extensions:User',
             'volume = rocker.volume_extension:Volume',

src/rocker/rmw_extension.py

@@ -0,0 +1,63 @@
+# Copyright 2024 Open Source Robotics Foundation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from argparse import ArgumentTypeError
+import os
+import pkgutil
+
+from .em import empy_expand
+from rocker.extensions import RockerExtension
+from rocker.extensions import name_to_argument
+
+
+class RMW(RockerExtension):
+    @staticmethod
+    def get_name():
+        return 'rmw'
+
+    def __init__(self):
+        self._env_subs = None
+        self.name = RMW.get_name()
+
+    def get_docker_args(self, cli_args):
+        implementation = cli_args.get('rmw')
+        args = f' -e RMW_IMPLEMENTATION=rmw_{implementation}_cpp'
+        return args #% self.get_environment_subs()
+
+    def get_environment_subs(self):
+        if not self._env_subs:
+            self._env_subs = {}
+        return self._env_subs
+
+    def get_preamble(self, cliargs):
+        return ''
+
+    def get_snippet(self, cliargs):
+        snippet = pkgutil.get_data('rocker', 'templates/%s_snippet.Dockerfile.em' % self.get_name()).decode('utf-8')
+        data = self.get_environment_subs()
+        # data['rosdistro'] = cliargs.get('rosdistro', 'rolling')
+        data['rmw'] = cliargs.get('rmw', None)
+        # data['rosdistro'] = 'rolling'
+        return empy_expand(snippet, data)
+
+    @staticmethod
+    def register_arguments(parser, defaults={}):
+        parser.add_argument(name_to_argument(RMW.get_name()),
+            default=defaults.get('rmw', 'fastrtps'),
+            nargs='?',
+            help="Set the default RMW implementation")
+
+        # parser.add_argument('rosdistro',
+        #     default=defaults.get('rosdistro', None),
+        #     help="Set the default rosdistro, else autodetect")

src/rocker/templates/rmw_snippet.Dockerfile.em

@@ -0,0 +1,13 @@
+# workspace development helpers
+
+
+@[ if rmw ]@
+RUN if [ -z "${ROS_DISTRO}" ]; then echo "ROS_DISTRO is unset cannot override RMW" ; exit 1 ; fi \
+ && apt-get update \
+ && apt-get install -y \
+    ros-${ROS_DISTRO}-rmw-@(rmw)-cpp \
+    ros-${ROS_DISTRO}-rmw-dds-common \
+ && apt-get clean
+@[ end if ]@
+
+# working around recent upgrade of dds-common from 2.x to 3.x which is out of date in the image