Composition API

ros2component/ros2component/api/__init__.py

@@ -14,8 +14,6 @@
 
 from collections import namedtuple
 import subprocess
-
-from ament_index_python import get_resource
 from ament_index_python import get_resources
 from ament_index_python import has_resource
 
@@ -32,37 +30,62 @@
 from ros2pkg.api import get_executable_paths
 from ros2pkg.api import PackageNotFound
 
-COMPONENTS_RESOURCE_TYPE = 'rclcpp_components'
+from .component_searcher import ComponentSearcher
+
+COMPONENTS_RESOURCE_TYPES = ['rclcpp_components', 'rclpy_components']
+
+try:
+    from importlib.metadata import entry_points
+except ImportError:
+    from importlib_meatadata import entry_points
+
+# TODO Make the process lazy or provide a explict init function
+# Try to find the loaders:
+res_searchers = {}
+eps = entry_points()
+for component_res_type in COMPONENTS_RESOURCE_TYPES:
+    searcher_entrypoints = eps.get(component_res_type+'.searcher', None)
+    if searcher_entrypoints:
+        # TODO What if there are multiple registered searchers?
+        component_class = searcher_entrypoints[0].load()
+        res_searchers[component_res_type] = component_class(component_res_type)
 
 
 def get_package_names_with_component_types():
     """Get the names of all packages that register component types in the ament index."""
-    return list(get_resources(COMPONENTS_RESOURCE_TYPE).keys())
+    package_names = dict()
+    for res_type in COMPONENTS_RESOURCE_TYPES:
+        package_names[res_type] = list(get_resources(res_type).keys())
+    return package_names
 
 
 def get_package_component_types(*, package_name=None):
     """
-    Get all component types registered in the ament index for the given package.
+    Get all component types registered for the given package.
 
     :param package_name: whose component types are to be retrieved.
     :return: a list of component type names.
     """
-    if not has_resource(COMPONENTS_RESOURCE_TYPE, package_name):
-        return []
-    component_registry, _ = get_resource(COMPONENTS_RESOURCE_TYPE, package_name)
-    return [line.split(';')[0] for line in component_registry.splitlines()]
+    component_types = []
+    global res_searchers
+    for resource_component_type, searcher in res_searchers.items():
+        if has_resource(resource_component_type, package_name):
+            component_types.extend(searcher.get_package_component_types(package_name))
+    return component_types
 
 
 def get_registered_component_types():
     """
-    Get all component types registered in the ament index.
+    Get all registered component types.
 
     :return: a list of (package name, component type names) tuples.
     """
-    return [
-        (package_name, get_package_component_types(package_name=package_name))
-        for package_name in get_package_names_with_component_types()
-    ]
+    global res_searchers
+    registered_component_types = []
+    for res_type, searcher in res_searchers.items():
+        component_types = searcher.get_component_types()
+        registered_component_types.extend(component_types)
+    return registered_component_types
 
 
 ComponentInfo = namedtuple('Component', ('uid', 'name'))
@@ -395,12 +418,12 @@ def add_component_arguments(parser):
     )
 
 
-def run_standalone_container(*, container_node_name):
+def run_standalone_container(*, container_node_name, component_type='rclcpp_components'):
     """Run a standalone component container."""
     try:
-        paths = get_executable_paths(package_name='rclcpp_components')
+        paths = get_executable_paths(package_name=component_type)
     except PackageNotFound:
-        raise RuntimeError("Package 'rclcpp_components' not found")
+        raise RuntimeError("Package '%s' not found" % component_type)
 
     executable_path = next((p for p in paths if 'component_container' in p), None)
     if executable_path is None:

ros2component/ros2component/api/component_searcher.py

@@ -0,0 +1,32 @@
+# Copyright 2020 Open Source Robotics Foundation, Inc.
+#
+# 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.
+
+class ComponentSearcher:
+    """An abstract class providing interfaces to get component types"""
+
+    def __init__(self, component_resource_type):
+        self.component_resource_type = component_resource_type
+
+    def get_component_types(self):
+        """Get the registered component types
+        :return: a list of component types in the tuple(res type/package name, component name)
+        """
+        pass
+
+    def get_package_component_types(self, package_name):
+        """Get the registered component types in a package
+        :param package_name: whose component types are to be retrieved.
+        :return: a list of component types in the tuple(res type/package name, component name)
+        """
+        pass

ros2component/ros2component/verb/standalone.py

@@ -36,9 +36,15 @@ def add_arguments(self, parser, cli_name):
             default='standalone_container_' + uuid.uuid4().hex[:12],
             help='Name of the standalone container node to be run'
         )
+        parser.add_argument(
+            '-t', '--component-type',
+            default='rclcpp_components',
+            help='Component resource types, typically in the format rcl<language>_components'
+        )
 
     def main(self, *, args):
-        container = run_standalone_container(container_node_name=args.container_node_name)
+        container = run_standalone_container(container_node_name=args.container_node_name,
+                                             component_type=args.component_type)
 
         with DirectNode(args) as node:
             try: