Use UninitializedStaticallyTypedParameterException

Signed-off-by: Mohammad Farzan <m2_farzan@yahoo.com>

Author: m2-farzan

rclcpp/include/rclcpp/exceptions/exceptions.hpp

@@ -254,6 +254,23 @@ class InvalidParameterTypeException : public std::runtime_error
   {}
 };
 
+/// Thrown if user attempts to create an uninitialized statically typed parameter
+/**
+ * (see https://github.com/ros2/rclcpp/issues/1691)
+ */
+class UninitializedStaticallyTypedParameterException : public std::runtime_error
+{
+public:
+  /// Construct an instance.
+  /**
+   * \param[in] name the name of the parameter.
+   */
+  RCLCPP_PUBLIC
+  UninitializedStaticallyTypedParameterException(const std::string & name)
+  : std::runtime_error("Statically typed parameter '" + name + "' must be initialized.")
+  {}
+};
+
 /// Thrown if parameter is already declared.
 class ParameterAlreadyDeclaredException : public std::runtime_error
 {

rclcpp/include/rclcpp/node_impl.hpp

@@ -220,12 +220,16 @@ Node::declare_parameter(
   // get advantage of parameter value template magic to get
   // the correct rclcpp::ParameterType from ParameterT
   rclcpp::ParameterValue value{ParameterT{}};
-  return this->declare_parameter(
-    name,
-    value.get_type(),
-    parameter_descriptor,
-    ignore_override
-  ).get<ParameterT>();
+  try {
+    return this->declare_parameter(
+      name,
+      value.get_type(),
+      parameter_descriptor,
+      ignore_override
+    ).get<ParameterT>();
+  } catch (const ParameterTypeException & ex) {
+    throw exceptions::UninitializedStaticallyTypedParameterException(name);
+  }
 }
 
 template<typename ParameterT>

rclcpp/test/rclcpp/test_node.cpp

@@ -690,6 +690,12 @@ TEST_F(TestNode, declare_parameter_with_overrides) {
           "parameter_type_mismatch", rclcpp::ParameterType::PARAMETER_INTEGER);},
       rclcpp::exceptions::InvalidParameterTypeException);
   }
+  {
+    // statically typed parameter must be initialized
+    EXPECT_THROW(
+      {node->declare_parameter<std::string>("static_and_uninitialized");},
+      rclcpp::exceptions::UninitializedStaticallyTypedParameterException);
+  }
   {
     // cannot pass an expected type and a descriptor with dynamic_typing=True
     rcl_interfaces::msg::ParameterDescriptor descriptor{};