Ensure load_composable_nodes respects condition (#339)

launch_ros/launch_ros/actions/load_composable_nodes.py

@@ -229,23 +229,31 @@ def execute(
 
         # Generate load requests before execute() exits to avoid race with context changing
         # due to scope change (e.g. if loading nodes from within a GroupAction).
-        load_node_requests = [
-            get_composable_node_load_request(node_description, context)
-            for node_description in self.__composable_node_descriptions
-        ]
-
-        context.add_completion_future(
-            context.asyncio_loop.run_in_executor(
-                None, self._load_in_sequence, load_node_requests, context
+        load_node_requests = []
+        for node_description in self.__composable_node_descriptions:
+            request = get_composable_node_load_request(node_description, context)
+            # The request can be None if the node description's condition evaluates to False
+            if request is not None:
+                load_node_requests.append(request)
+
+        if load_node_requests:
+            context.add_completion_future(
+                context.asyncio_loop.run_in_executor(
+                    None, self._load_in_sequence, load_node_requests, context
+                )
             )
-        )
 
 
 def get_composable_node_load_request(
     composable_node_description: ComposableNode,
     context: LaunchContext
 ):
     """Get the request that will be sent to the composable node container."""
+    if composable_node_description.condition() is not None:
+        if not composable_node_description.condition().evaluate(context):
+            # Return no request if the node description's condition evaluates to False
+            return None
+
     request = composition_interfaces.srv.LoadNode.Request()
     request.package_name = perform_substitutions(
         context, composable_node_description.package

test_launch_ros/test/test_launch_ros/actions/test_load_composable_nodes.py

@@ -22,6 +22,7 @@
 from launch import LaunchDescription
 from launch import LaunchService
 from launch.actions import GroupAction
+from launch.conditions import IfCondition
 from launch_ros.actions import LoadComposableNodes
 from launch_ros.actions import PushROSNamespace
 from launch_ros.actions import SetRemap
@@ -99,6 +100,7 @@ def _load_composable_node(
     plugin,
     name,
     namespace='',
+    condition=None,
     parameters=None,
     remappings=None,
     target_container=f'/{TEST_CONTAINER_NAME}'
@@ -107,6 +109,7 @@ def _load_composable_node(
         target_container=target_container,
         composable_node_descriptions=[
             ComposableNode(
+                condition=condition,
                 package=package,
                 plugin=plugin,
                 name=name,
@@ -150,6 +153,41 @@ def test_load_node(mock_component_container):
     assert len(request.extra_arguments) == 0
 
 
+def test_load_node_with_conditions(mock_component_container):
+    """Test loading nodes with conditions scoped to a group."""
+    context = _assert_launch_no_errors([
+        _load_composable_node(
+            package='foo_package',
+            plugin='bar_plugin',
+            name='test_node_name_true',
+            namespace='test_node_namespace',
+            condition=IfCondition('True')
+        ),
+        _load_composable_node(
+            package='foo_package',
+            plugin='bar_plugin',
+            name='test_node_name_false',
+            namespace='test_node_namespace',
+            condition=IfCondition('False')
+        )
+    ])
+
+    # Check that launch is aware of loaded component
+    assert get_node_name_count(context, '/test_node_namespace/test_node_name_true') == 1
+    assert get_node_name_count(context, '/test_node_namespace/test_node_name_false') == 0
+
+    # Check that container recieved correct request
+    assert len(mock_component_container.requests) == 1
+    request = mock_component_container.requests[0]
+    assert request.package_name == 'foo_package'
+    assert request.plugin_name == 'bar_plugin'
+    assert request.node_name == 'test_node_name_true'
+    assert request.node_namespace == '/test_node_namespace'
+    assert len(request.remap_rules) == 0
+    assert len(request.parameters) == 0
+    assert len(request.extra_arguments) == 0
+
+
 def test_load_node_with_remaps(mock_component_container):
     """Test loading a node with remappings."""
     context = _assert_launch_no_errors([
@@ -515,3 +553,44 @@ def test_load_node_with_namespace_in_group(mock_component_container):
     assert len(request.remap_rules) == 0
     assert len(request.parameters) == 0
     assert len(request.extra_arguments) == 0
+
+
+def test_load_node_with_condition_in_group(mock_component_container):
+    """Test loading nodes with conditions scoped to a group."""
+    context = _assert_launch_no_errors([
+        GroupAction(
+            [
+                PushROSNamespace('foo'),
+                _load_composable_node(
+                    package='foo_package',
+                    plugin='bar_plugin',
+                    name='test_node_name_true',
+                    namespace='test_node_namespace',
+                    condition=IfCondition('True')
+                ),
+                _load_composable_node(
+                    package='foo_package',
+                    plugin='bar_plugin',
+                    name='test_node_name_false',
+                    namespace='test_node_namespace',
+                    condition=IfCondition('False')
+                ),
+            ],
+            scoped=True,
+        ),
+    ])
+
+    # Check that launch is aware of loaded component
+    assert get_node_name_count(context, '/foo/test_node_namespace/test_node_name_true') == 1
+    assert get_node_name_count(context, '/foo/test_node_namespace/test_node_name_false') == 0
+
+    # Check that container recieved correct request
+    assert len(mock_component_container.requests) == 1
+    request = mock_component_container.requests[0]
+    assert request.package_name == 'foo_package'
+    assert request.plugin_name == 'bar_plugin'
+    assert request.node_name == 'test_node_name_true'
+    assert request.node_namespace == '/foo/test_node_namespace'
+    assert len(request.remap_rules) == 0
+    assert len(request.parameters) == 0
+    assert len(request.extra_arguments) == 0