subordinate node consistent behavior and update docstring.

rclcpp/include/rclcpp/node.hpp

@@ -1559,6 +1559,10 @@ class Node : public std::enable_shared_from_this<Node>
    * which has been created using an existing instance of this class, but which
    * has an additional sub-namespace (short for subordinate namespace)
    * associated with it.
+   * A suboardinate node and an instance of this class share all the node interfaces
+   * such as `rclcpp::node_interfaces::NodeParameterInterface`.
+   * Suboardinate nodes are primarily used to organize namespaces and provide a
+   * hierarchical structure, but they are not meant to be completely independent nodes.
    * The sub-namespace will extend the node's namespace for the purpose of
    * creating additional entities, such as Publishers, Subscriptions, Service
    * Clients and Servers, and so on.

rclcpp/include/rclcpp/node_impl.hpp

@@ -323,11 +323,9 @@ template<typename ParameterT>
 bool
 Node::get_parameter(const std::string & name, ParameterT & parameter) const
 {
-  std::string sub_name = extend_name_with_sub_namespace(name, this->get_sub_namespace());
-
   rclcpp::Parameter parameter_variant;
 
-  bool result = get_parameter(sub_name, parameter_variant);
+  bool result = get_parameter(name, parameter_variant);
   if (result) {
     parameter = static_cast<ParameterT>(parameter_variant.get_value<ParameterT>());
   }
@@ -342,9 +340,7 @@ Node::get_parameter_or(
   ParameterT & parameter,
   const ParameterT & alternative_value) const
 {
-  std::string sub_name = extend_name_with_sub_namespace(name, this->get_sub_namespace());
-
-  bool got_parameter = get_parameter(sub_name, parameter);
+  bool got_parameter = get_parameter(name, parameter);
   if (!got_parameter) {
     parameter = alternative_value;
   }

rclcpp/src/rclcpp/node.cpp

@@ -689,7 +689,7 @@ Node::create_generic_client(
     node_base_,
     node_graph_,
     node_services_,
-    service_name,
+    extend_name_with_sub_namespace(service_name, this->get_sub_namespace()),
     service_type,
     qos,
     group);

rclcpp/test/rclcpp/test_generic_client.cpp

@@ -221,7 +221,7 @@ TEST_F(TestGenericClient, wait_for_service) {
 TEST_F(TestGenericClientSub, construction_and_destruction) {
   {
     auto client = subnode->create_generic_client("test_service", "test_msgs/srv/Empty");
-    EXPECT_STREQ(client->get_service_name(), "/ns/test_service");
+    EXPECT_STREQ(client->get_service_name(), "/ns/sub_ns/test_service");
   }
 
   {

rclcpp/test/rclcpp/test_node.cpp

@@ -306,6 +306,39 @@ TEST_F(TestNode, subnode_get_name_and_namespace) {
     }, rclcpp::exceptions::NameValidationError);
   }
 }
+
+TEST_F(TestNode, subnode_parameter_operation) {
+  auto node = std::make_shared<rclcpp::Node>("my_node", "ns");
+  auto subnode = node->create_sub_node("sub_ns");
+
+  auto value = subnode->declare_parameter("param", 5);
+  EXPECT_EQ(value, 5);
+  // node and sub-node shares NodeParameterInterface, so expecting the exception.
+  EXPECT_THROW(
+    node->declare_parameter("param", 0),
+    rclcpp::exceptions::ParameterAlreadyDeclaredException);
+  rclcpp::Parameter param;
+
+  node->get_parameter("param", param);
+  EXPECT_EQ(param.get_value<int>(), 5);
+  subnode->get_parameter("param", param);
+  EXPECT_EQ(param.get_value<int>(), 5);
+
+  int param_int;
+  node->get_parameter("param", param_int);
+  EXPECT_EQ(param_int, 5);
+  subnode->get_parameter("param", param_int);
+  EXPECT_EQ(param_int, 5);
+
+  EXPECT_EQ(node->get_parameter_or("param", 333), 5);
+  EXPECT_EQ(subnode->get_parameter_or("param", 666), 5);
+
+  node->get_parameter_or("param", param_int, 333);
+  EXPECT_EQ(param_int, 5);
+  subnode->get_parameter_or("param", param_int, 666);
+  EXPECT_EQ(param_int, 5);
+}
+
 /*
    Testing node construction and destruction.
  */