Add an outline for the "passthrough controller"

passthrough_controller/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(passthrough_controller LANGUAGES CXX)
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang)")
+  add_compile_options(-Wall -Wextra)
+endif()
+
+set(THIS_PACKAGE_INCLUDE_DEPENDS
+  control_msgs
+  controller_interface
+  hardware_interface
+  parameter_traits
+  pluginlib
+  rclcpp
+  rclcpp_lifecycle
+  realtime_tools
+)
+
+find_package(ament_cmake REQUIRED)
+find_package(backward_ros REQUIRED)
+foreach(Dependency IN ITEMS ${THIS_PACKAGE_INCLUDE_DEPENDS})
+  find_package(${Dependency} REQUIRED)
+endforeach()
+
+add_library(passthrough_controller SHARED
+  src/passthrough_controller.cpp
+)
+target_compile_features(passthrough_controller PUBLIC cxx_std_17)
+target_include_directories(passthrough_controller PUBLIC
+  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+  $<INSTALL_INTERFACE:include/passthrough_controller>
+)
+# target_link_libraries(passthrough_controller PUBLIC
+#   passthrough_controller_parameters
+# )
+ament_target_dependencies(passthrough_controller PUBLIC ${THIS_PACKAGE_INCLUDE_DEPENDS})
+
+# Causes the visibility macros to use dllexport rather than dllimport,
+# which is appropriate when building the dll but not consuming it.
+target_compile_definitions(passthrough_controller PRIVATE "passthrough_controller_BUILDING_DLL")
+
+pluginlib_export_plugin_description_file(controller_interface passthrough_controller.xml)
+
+if(BUILD_TESTING)
+  find_package(ament_cmake_gmock REQUIRED)
+  find_package(controller_manager REQUIRED)
+  find_package(ros2_control_test_assets REQUIRED)
+
+  ament_add_gmock(test_load_controller test/test_load_controller.cpp)
+  target_include_directories(test_load_controller PRIVATE include)
+  ament_target_dependencies(
+    test_load_controller
+    controller_manager
+    ros2_control_test_assets
+  )
+endif()
+
+install(
+  DIRECTORY include/
+  DESTINATION include/passthrough_controller
+)
+
+install(TARGETS
+    passthrough_controller
+  EXPORT export_passthrough_controller
+  RUNTIME DESTINATION bin
+  ARCHIVE DESTINATION lib
+  LIBRARY DESTINATION lib
+)
+
+ament_export_targets(export_passthrough_controller HAS_LIBRARY_TARGET)
+ament_export_dependencies(${THIS_PACKAGE_INCLUDE_DEPENDS})
+ament_package()

passthrough_controller/include/passthrough_controller/passthrough_controller.hpp

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+// Copyright (c) 2023, PAL Robotics
+//
+// 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.
+
+#ifndef PASSTHROUGH_CONTROLLER__PASSTHROUGH_CONTROLLER_HPP_
+#define PASSTHROUGH_CONTROLLER__PASSTHROUGH_CONTROLLER_HPP_
+
+#include <controller_interface/chainable_controller_interface.hpp>
+
+#include "passthrough_controller/visibility_control.h"
+
+namespace passthrough_controller
+{
+class PassthroughController : public controller_interface::ChainableControllerInterface
+{
+public:
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  PassthroughController(){}
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  controller_interface::CallbackReturn on_init() override
+  {
+    return controller_interface::CallbackReturn::SUCCESS;
+  }
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  controller_interface::InterfaceConfiguration command_interface_configuration() const override
+  {
+    controller_interface::InterfaceConfiguration command_interfaces_config;
+    return command_interfaces_config;
+  }
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  controller_interface::InterfaceConfiguration state_interface_configuration() const override
+  {
+    controller_interface::InterfaceConfiguration state_interfaces_config;
+    return state_interfaces_config;
+  }
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  controller_interface::return_type update_reference_from_subscribers(const rclcpp::Time & /* time */, const rclcpp::Duration & /* period */) override
+  {
+    return controller_interface::return_type::OK;
+  }
+
+protected:
+  std::vector<hardware_interface::CommandInterface> on_export_reference_interfaces() override
+  {
+    return std::vector<hardware_interface::CommandInterface>();
+  }
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  bool on_set_chained_mode(bool /* chained_mode */) override
+  {
+    return true;
+  }
+
+  PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+  controller_interface::return_type update_and_write_commands(
+  const rclcpp::Time & /* time */, const rclcpp::Duration & /* period */) override
+  {
+    return controller_interface::return_type::OK;
+  }
+};
+
+}  // namespace passthrough_controller
+
+#endif  // PASSTHROUGH_CONTROLLER__PASSTHROUGH_CONTROLLER_HPP_

passthrough_controller/include/passthrough_controller/visibility_control.h

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+// Copyright (c) 2023, PAL Robotics
+//
+// 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.
+
+#ifndef PASSTHROUGH_CONTROLLER__VISIBILITY_CONTROL_H_
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_CONTROL_H_
+
+// This logic was borrowed (then namespaced) from the examples on the gcc wiki:
+//     https://gcc.gnu.org/wiki/Visibility
+
+#if defined _WIN32 || defined __CYGWIN__
+#ifdef __GNUC__
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_EXPORT __attribute__((dllexport))
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_IMPORT __attribute__((dllimport))
+#else
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_EXPORT __declspec(dllexport)
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_IMPORT __declspec(dllimport)
+#endif
+#ifdef PASSTHROUGH_CONTROLLER__VISIBILITY_BUILDING_DLL
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC PASSTHROUGH_CONTROLLER__VISIBILITY_EXPORT
+#else
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC PASSTHROUGH_CONTROLLER__VISIBILITY_IMPORT
+#endif
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC_TYPE PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_LOCAL
+#else
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_EXPORT __attribute__((visibility("default")))
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_IMPORT
+#if __GNUC__ >= 4
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC __attribute__((visibility("default")))
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_LOCAL __attribute__((visibility("hidden")))
+#else
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_LOCAL
+#endif
+#define PASSTHROUGH_CONTROLLER__VISIBILITY_PUBLIC_TYPE
+#endif
+
+#endif  // PASSTHROUGH_CONTROLLER__VISIBILITY_CONTROL_H_

passthrough_controller/package.xml

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+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+<package format="3">
+  <name>passthrough_controller</name>
+  <version>0.0.0</version>
+  <description>A simple demo of chainable controllers. It passes commands through without change.</description>
+  <maintainer email="[email protected]">Sai Kishor Kothakota</maintainer>
+  <maintainer email="[email protected]">Andy Zelenak</maintainer>
+  <license>Apache-2.0</license>
+
+  <buildtool_depend>ament_cmake</buildtool_depend>
+
+  <depend>control_msgs</depend>
+  <depend>controller_interface</depend>
+  <depend>hardware_interface</depend>
+  <depend>parameter_traits</depend>
+  <depend>pluginlib</depend>
+  <depend>rclcpp</depend>
+  <depend>rclcpp_lifecycle</depend>
+  <depend>realtime_tools</depend>
+
+  <test_depend>ament_cmake_gmock</test_depend>
+  <test_depend>controller_manager</test_depend>
+  <test_depend>ros2_control_test_assets</test_depend>
+
+  <export>
+    <build_type>ament_cmake</build_type>
+  </export>
+</package>

passthrough_controller/passthrough_controller.xml

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+<library path="passthrough_controller">
+  <class name="passthrough_controller/PassthroughController"
+         type="passthrough_controller::PassthroughController"
+         base_class_type="controller_interface::ChainableControllerInterface">
+    <description>
+      A simple demo of chainable controllers. It passes commands through without change.
+    </description>
+  </class>
+</library>

passthrough_controller/src/passthrough_controller.cpp

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+// Copyright (c) 2023, PAL Robotics
+//
+// 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.
+
+#include "passthrough_controller/passthrough_controller.hpp"
+
+namespace passthrough_controller
+{
+
+} // namespace passthrough_controller
+
+#include "pluginlib/class_list_macros.hpp"
+
+PLUGINLIB_EXPORT_CLASS(
+  passthrough_controller::PassthroughController, controller_interface::ChainableControllerInterface)

passthrough_controller/test/test_load_controller.cpp

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+// Copyright (c) 2023, PAL Robotics
+//
+// 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.
+
+#include <gmock/gmock.h>
+#include <memory>
+
+#include "controller_manager/controller_manager.hpp"
+#include "hardware_interface/resource_manager.hpp"
+#include "rclcpp/executor.hpp"
+#include "rclcpp/executors/single_threaded_executor.hpp"
+#include "rclcpp/utilities.hpp"
+#include "ros2_control_test_assets/descriptions.hpp"
+
+TEST(TestLoadPidController, load_controller)
+{
+  rclcpp::init(0, nullptr);
+
+  std::shared_ptr<rclcpp::Executor> executor =
+    std::make_shared<rclcpp::executors::SingleThreadedExecutor>();
+
+  controller_manager::ControllerManager cm(
+    std::make_unique<hardware_interface::ResourceManager>(
+      ros2_control_test_assets::minimal_robot_urdf),
+    executor, "test_controller_manager");
+
+  ASSERT_NO_THROW(cm.load_controller("test_passthrough_controller", "passthrough_controller/PassthroughController"));
+
+  rclcpp::shutdown();
+}