Support type description service (#1146)

This PR adds support for the ROS 2 Type Description Service, including native bindings, JavaScript API, test coverage, build integration, and an option to start the service automatically.

- Introduces C++ N-API bindings for the type description service and integrates them in the module initialization.
- Implements a JavaScript `TypeDescriptionService` class, updates `NodeOptions`/`Node` to optionally start the service, and adds tests.
- Updates `binding.gyp` to include the new source and extends test files to handle distro version differences.

See doc: https://docs.ros.org/en/jazzy/Releases/Release-Jazzy-Jalisco.html#add-get-type-description-service

Fix: #1143

Author: minggangw

binding.gyp

@@ -166,6 +166,14 @@
             ]
           }
         ],
+        [
+          # After Humble, e.g., Jazzy, Kilted.
+          'ros_version > 2205', {
+            'sources': [
+              './src/rcl_type_description_service_bindings.cpp',
+            ]
+          }
+        ],
         [
           'runtime=="electron"', {
             "defines": ["NODE_RUNTIME_ELECTRON=1"]

lib/node.js

@@ -39,6 +39,7 @@ const Service = require('./service.js');
 const Subscription = require('./subscription.js');
 const TimeSource = require('./time_source.js');
 const Timer = require('./timer.js');
+const TypeDescriptionService = require('./type_description_service.js');
 const Entity = require('./entity.js');
 
 // Parameter event publisher constants
@@ -101,6 +102,7 @@ class Node extends rclnodejs.ShadowNode {
     this._parameterDescriptors = new Map();
     this._parameters = new Map();
     this._parameterService = null;
+    this._typeDescriptionService = null;
     this._parameterEventPublisher = null;
     this._setParametersCallbacks = [];
     this._logger = new Logging(rclnodejs.getNodeLoggerName(this.handle));
@@ -147,6 +149,14 @@ class Node extends rclnodejs.ShadowNode {
       this._parameterService = new ParameterService(this);
       this._parameterService.start();
     }
+
+    if (
+      DistroUtils.getDistroId() >= DistroUtils.getDistroId('jazzy') &&
+      options.startTypeDescriptionService
+    ) {
+      this._typeDescriptionService = new TypeDescriptionService(this);
+      this._typeDescriptionService.start();
+    }
   }
 
   execute(handles) {

lib/node_options.js

@@ -26,16 +26,19 @@ class NodeOptions {
    * @param {boolean} [startParameterServices=true]
    * @param {array} [parameterOverrides=[]]
    * @param {boolean} [automaticallyDeclareParametersFromOverrides=false]
+   * @param {boolean} [startTypeDescriptionService=true]
    */
   constructor(
     startParameterServices = true,
     parameterOverrides = [],
-    automaticallyDeclareParametersFromOverrides = false
+    automaticallyDeclareParametersFromOverrides = false,
+    startTypeDescriptionService = true
   ) {
     this._startParameterServices = startParameterServices;
     this._parameterOverrides = parameterOverrides;
     this._automaticallyDeclareParametersFromOverrides =
       automaticallyDeclareParametersFromOverrides;
+    this._startTypeDescriptionService = startTypeDescriptionService;
   }
 
   /**
@@ -105,6 +108,23 @@ class NodeOptions {
     this._automaticallyDeclareParametersFromOverrides = declareParamsFlag;
   }
 
+  /**
+   * Get the startTypeDescriptionService option, only available for ROS2 > Humble.
+   * Default value = true;
+   * @returns {boolean} - true if the type description service is enabled.
+   */
+  get startTypeDescriptionService() {
+    return this._startTypeDescriptionService;
+  }
+
+  /**
+   * Set startTypeDescriptionService, only available for ROS2 > Humble
+   * @param {boolean} willStartTypeDescriptionService
+   */
+  set startTypeDescriptionService(willStartTypeDescriptionService) {
+    this._startTypeDescriptionService = willStartTypeDescriptionService;
+  }
+
   /**
    * Return an instance configured with default options.
    * @returns {NodeOptions} - An instance with default values.

lib/type_description_service.js

@@ -0,0 +1,82 @@
+// Copyright (c) 2025, The Robot Web Tools Contributors
+//
+// 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.
+
+'use strict';
+
+const loader = require('./interface_loader.js');
+const rclnodejs = require('bindings')('rclnodejs');
+const Service = require('./service.js');
+
+// This class is used to create a TypeDescriptionService which can be used to
+// retrieve information about types used by the node’s publishers, subscribers,
+// services or actions.
+class TypeDescriptionService {
+  constructor(node) {
+    this._node = node;
+    this._serviceName = this._node.name() + '/get_type_description';
+    this._typeDescriptionServiceHandle = rclnodejs.initTypeDescriptionService(
+      this._node.handle
+    );
+    this._typeClass = loader.loadInterface(
+      'type_description_interfaces/srv/GetTypeDescription'
+    );
+    this._typeDescriptionService = null;
+  }
+
+  start() {
+    if (this._typeDescriptionService) {
+      return;
+    }
+
+    this._typeDescriptionService = new Service(
+      this._node.handle,
+      this._typeDescriptionServiceHandle,
+      this._serviceName,
+      this._typeClass,
+      this._node._validateOptions(undefined),
+      (request, response) => {
+        const responseToBeSent = new this._typeClass.Response();
+        const requestReceived = new this._typeClass.Request(request);
+        rclnodejs.handleRequest(
+          this._node.handle,
+          requestReceived.serialize(),
+          responseToBeSent.serialize()
+        );
+        responseToBeSent.deserialize(responseToBeSent.refObject);
+        rclnodejs.sendResponse(
+          this._typeDescriptionServiceHandle,
+          responseToBeSent.serialize(),
+          response._header
+        );
+        return null;
+      }
+    );
+    this._node._services.push(this._typeDescriptionService);
+    this._node.syncHandles();
+  }
+
+  /**
+   * Get the node this
+   * @return {Node} - The supported node.
+   */
+  get node() {
+    return this._node;
+  }
+
+  static toTypeHash(topicTypeHash) {
+    return `RIHS0${topicTypeHash.version}_${topicTypeHash.value.toString('hex')}`;
+  }
+}
+
+module.exports = TypeDescriptionService;

src/addon.cpp

@@ -34,6 +34,9 @@
 #include "rcl_subscription_bindings.h"
 #include "rcl_time_point_bindings.h"
 #include "rcl_timer_bindings.h"
+#if ROS_VERSION > 2205  // ROS2 > Humble
+#include "rcl_type_description_service_bindings.h"
+#endif
 #include "rcl_utilities.h"
 #include "shadow_node.h"
 
@@ -79,6 +82,9 @@ Napi::Object InitModule(Napi::Env env, Napi::Object exports) {
   rclnodejs::InitSubscriptionBindings(env, exports);
   rclnodejs::InitTimePointBindings(env, exports);
   rclnodejs::InitTimerBindings(env, exports);
+#if ROS_VERSION > 2205  // ROS2 > Humble
+  rclnodejs::InitTypeDescriptionServiceBindings(env, exports);
+#endif
   rclnodejs::InitLifecycleBindings(env, exports);
   rclnodejs::ShadowNode::Init(env, exports);
   rclnodejs::RclHandle::Init(env, exports);

src/rcl_type_description_service_bindings.cpp

@@ -0,0 +1,79 @@
+// Copyright (c) 2025, The Robot Web Tools Contributors
+//
+// 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 "rcl_type_description_service_bindings.h"
+
+#include <napi.h>
+#include <rcl/rcl.h>
+#include <rmw/types.h>
+
+#include "rcl_handle.h"
+
+namespace rclnodejs {
+
+Napi::Value InitTypeDescriptionService(const Napi::CallbackInfo& info) {
+  Napi::Env env = info.Env();
+  RclHandle* node_handle = RclHandle::Unwrap(info[0].As<Napi::Object>());
+  rcl_node_t* node = reinterpret_cast<rcl_node_t*>(node_handle->ptr());
+  rcl_service_t* service =
+      reinterpret_cast<rcl_service_t*>(malloc(sizeof(rcl_service_t)));
+  *service = rcl_get_zero_initialized_service();
+  rcl_ret_t ret = rcl_node_type_description_service_init(service, node);
+  if (RCL_RET_OK != ret) {
+    Napi::Error::New(env, "Failed to initialize type description service")
+        .ThrowAsJavaScriptException();
+  }
+
+  auto service_handle =
+      RclHandle::NewInstance(env, service, node_handle, [node, env](void* ptr) {
+        rcl_service_t* service = reinterpret_cast<rcl_service_t*>(ptr);
+        rcl_ret_t ret = rcl_service_fini(service, node);
+        if (RCL_RET_OK != ret) {
+          Napi::Error::New(env, "Failed to destroy type description service")
+              .ThrowAsJavaScriptException();
+        }
+        free(ptr);
+      });
+  return service_handle;
+}
+
+Napi::Value HandleRequest(const Napi::CallbackInfo& info) {
+  Napi::Env env = info.Env();
+  rcl_node_t* node = reinterpret_cast<rcl_node_t*>(
+      RclHandle::Unwrap(info[0].As<Napi::Object>())->ptr());
+  void* request = info[1].As<Napi::Buffer<char>>().Data();
+  void* taken_response = info[2].As<Napi::Buffer<char>>().Data();
+
+  rmw_request_id_t header;
+  rcl_node_type_description_service_handle_request(
+      node, &header,
+      static_cast<
+          type_description_interfaces__srv__GetTypeDescription_Request*>(
+          request),
+      static_cast<
+          type_description_interfaces__srv__GetTypeDescription_Response*>(
+          taken_response));
+  return env.Undefined();
+}
+
+Napi::Object InitTypeDescriptionServiceBindings(Napi::Env env,
+                                                Napi::Object exports) {
+  exports.Set("handleRequest", Napi::Function::New(env, HandleRequest));
+  exports.Set("initTypeDescriptionService",
+              Napi::Function::New(env, InitTypeDescriptionService));
+
+  return exports;
+}
+
+}  // namespace rclnodejs

src/rcl_type_description_service_bindings.h

@@ -0,0 +1,27 @@
+// Copyright (c) 2025, The Robot Web Tools Contributors
+//
+// 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 SRC_RCL_TYPE_DESCRIPTION_SERVICE_BINDINGS_H_
+#define SRC_RCL_TYPE_DESCRIPTION_SERVICE_BINDINGS_H_
+
+#include <napi.h>
+
+namespace rclnodejs {
+
+Napi::Object InitTypeDescriptionServiceBindings(Napi::Env env,
+                                                Napi::Object exports);
+
+}
+
+#endif  // SRC_RCL_TYPE_DESCRIPTION_SERVICE_BINDINGS_H_

test/test-extra-destroy-methods.js

@@ -18,6 +18,7 @@ const assert = require('assert');
 const rclnodejs = require('../index.js');
 const assertUtils = require('./utils.js');
 const assertThrowsError = assertUtils.assertThrowsError;
+const DistroUtils = require('../lib/distro.js');
 
 describe('Node extra destroy methods testing', function () {
   before(function () {
@@ -88,9 +89,9 @@ describe('Node extra destroy methods testing', function () {
   it('destroyService()', function () {
     var node = rclnodejs.createNode('node4');
     const AddTwoInts = 'example_interfaces/srv/AddTwoInts';
+    const initialServiceCount = node._services.length;
     var service = node.createService(AddTwoInts, 'add_two_ints', () => {});
-    assert.deepStrictEqual(node._services.length, 7);
-
+    assert.deepStrictEqual(node._services.length, initialServiceCount + 1);
     assertThrowsError(
       function () {
         node.destroyService('service');
@@ -101,7 +102,7 @@ describe('Node extra destroy methods testing', function () {
     );
 
     node.destroyService(service);
-    assert.deepStrictEqual(node._services.length, 6);
+    assert.deepStrictEqual(node._services.length, initialServiceCount);
   });
 
   it('destroyTimer()', function () {