Add types to ParameterService

Since ROS2 Jazzy, parameter services support a service type of
rcl_interfaces/srv/GetParameterTypes, which can get a list of
parameter types associated with the requested parameters.

This patch implements:

1. Add service /node_name/get_parameters, which is used to get
   the parameter types.
2. Add unit test, Get_parameter_types, into test-parameter-service.js.

Meanwhile, this patch fixes the timeout issue when executing:

ros2 param list node_name

because of absence of /node_name/get_parameters.

Fix: #1024

Author: minggangw

lib/node.js

@@ -1273,6 +1273,26 @@ class Node extends rclnodejs.ShadowNode {
     return params;
   }
 
+  /**
+   * Get the types of given parameters.
+   *
+   * Return the types of given parameters.
+   *
+   * @param {string[]} [names] - The names of the declared parameters.
+   * @return {Uint8Array} - The types.
+   */
+  getParameterTypes(names = []) {
+    let types = [];
+
+    for (const name of names) {
+      const descriptor = this._parameterDescriptors.get(name);
+      if (descriptor) {
+        types.push(descriptor.type);
+      }
+    }
+    return types;
+  }
+
   /**
    * Get the names of all declared parameters.
    *

lib/parameter_service.js

@@ -110,6 +110,16 @@ class ParameterService {
       }
     );
 
+    // Create GetParameterTypes service.
+    const getParameterTypesServiceName = nodeName + '/get_parameter_types';
+    this._node.createService(
+      'rcl_interfaces/srv/GetParameterTypes',
+      getParameterTypesServiceName,
+      (request, response) => {
+        this._handleGetParameterTypes(request, response);
+      }
+    );
+
     // create SetParametersAtomically service
     const setParametersAtomicallyServiceName =
       nodeName + '/set_parameters_atomically';
@@ -266,6 +276,23 @@ class ParameterService {
     response.send(msg);
   }
 
+  /**
+   * Get a list of parameter types.
+   *
+   * request.names identifies the parameter types to get.
+   *
+   * @param {GetParameterTypes_Request} request - The client request.
+   * @param {GetParameterTypes_Response} response - The service response with
+   *    Uint8Array.
+   * @return {undefined} -
+   */
+  _handleGetParameterTypes(request, response) {
+    const types = this._node.getParameterTypes(request.names);
+    const msg = response.template;
+    msg.types = types;
+    response.send(msg);
+  }
+
   /**
    * Update a list of parameters atomically.
    *

test/test-parameter-service.js

@@ -367,4 +367,34 @@ describe('Parameter_server tests', function () {
       `Expected 3 parameter-events, received ${eventCount} events.`
     );
   });
+
+  it('Get_parameter_types', async function () {
+    const client = clientNode.createClient(
+      'rcl_interfaces/srv/GetParameterTypes',
+      'test_node/get_parameter_types'
+    );
+    await client.waitForService();
+
+    const ParamTypes = rclnodejs.require('rcl_interfaces/msg/ParameterType');
+    const request = new (rclnodejs.require(
+      'rcl_interfaces/srv/GetParameterTypes'
+    ).Request)();
+    request.names = ['p1', 'p2', 'A.p3'];
+    let success = false;
+
+    client.sendRequest(request, (response) => {
+      assert.deepEqual(response.types.length, 3);
+      assert.deepEqual(
+        response.types,
+        Uint8Array.from([
+          ParamTypes.PARAMETER_STRING,
+          ParamTypes.PARAMETER_INTEGER,
+          ParamTypes.PARAMETER_BOOL,
+        ])
+      );
+      success = true;
+    });
+    await assertUtils.createDelay(STD_WAIT);
+    assert.ok(success);
+  });
 });