Add InvalidParameterTypeException (#1027)

* Add InvalidParameterTypeException

Used to wrap the ParameterTypeException coming from ParameterValue::get() for improving the error message.

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

* Describe new exception

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

* Update tests

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

rclcpp/include/rclcpp/exceptions.hpp

@@ -226,6 +226,25 @@ class InvalidParameterValueException : public std::runtime_error
   using std::runtime_error::runtime_error;
 };
 
+/// Thrown if requested parameter type is invalid.
+/**
+ * Essentially the same as rclcpp::ParameterTypeException, but with parameter
+ * name in the error message.
+ */
+class InvalidParameterTypeException : public std::runtime_error
+{
+public:
+  /// Construct an instance.
+  /**
+   * \param[in] name the name of the parameter.
+   * \param[in] message custom exception message.
+   */
+  RCLCPP_PUBLIC
+  InvalidParameterTypeException(const std::string & name, const std::string message)
+  : std::runtime_error("parameter '" + name + "' has invalid type: " + message)
+  {}
+};
+
 /// Thrown if parameter is already declared.
 class ParameterAlreadyDeclaredException : public std::runtime_error
 {

rclcpp/include/rclcpp/node.hpp

@@ -301,7 +301,7 @@ public:
    *
    * If the type of the default value, and therefore also the type of return
    * value, differs from the initial value provided in the node options, then
-   * a rclcpp::ParameterTypeException may be thrown.
+   * a rclcpp::exceptions::InvalidParameterTypeException may be thrown.
    * To avoid this, use the declare_parameter() method which returns an
    * rclcpp::ParameterValue instead.
    *

rclcpp/include/rclcpp/node_impl.hpp

@@ -156,12 +156,16 @@ Node::declare_parameter(
   const rcl_interfaces::msg::ParameterDescriptor & parameter_descriptor,
   bool ignore_override)
 {
+  try {
     return this->declare_parameter(
       name,
       rclcpp::ParameterValue(default_value),
       parameter_descriptor,
       ignore_override
     ).get<ParameterT>();
+  } catch (const ParameterTypeException & ex) {
+    throw exceptions::InvalidParameterTypeException(name, ex.what());
+  }
 }
 
 template<typename ParameterT>

rclcpp/include/rclcpp/parameter.hpp

@@ -22,6 +22,7 @@
 #include <vector>
 
 #include "rcl_interfaces/msg/parameter.hpp"
+#include "rclcpp/exceptions.hpp"
 #include "rclcpp/parameter_value.hpp"
 #include "rclcpp/visibility_control.hpp"
 
@@ -221,8 +222,12 @@ template<typename T>
 decltype(auto)
 Parameter::get_value() const
 {
+  try {
     // use the helper to specialize for the ParameterValue and Parameter cases.
     return detail::get_value_helper<T>(this);
+  } catch (const ParameterTypeException & ex) {
+    throw exceptions::InvalidParameterTypeException(this->name_, ex.what());
+  }
 }
 
 }  // namespace rclcpp

rclcpp/test/test_node.cpp

@@ -574,7 +574,7 @@ TEST_F(TestNode, declare_parameter_with_overrides) {
     // default type and initial value type do not match
     EXPECT_THROW(
       {node->declare_parameter("parameter_type_mismatch", 42);},
-      rclcpp::ParameterTypeException);
+      rclcpp::exceptions::InvalidParameterTypeException);
   }
 }
 
@@ -1717,7 +1717,7 @@ TEST_F(TestNode, get_parameter_undeclared_parameters_not_allowed) {
       int value;
       node->get_parameter(name, value);
     },
-      rclcpp::ParameterTypeException);
+      rclcpp::exceptions::InvalidParameterTypeException);
   }
 }
 
@@ -1951,7 +1951,7 @@ TEST_F(TestNode, get_parameters_undeclared_parameters_not_allowed) {
       {
         node_local->get_parameters("", actual);
       },
-        rclcpp::ParameterTypeException);
+        rclcpp::exceptions::InvalidParameterTypeException);
     }
   }
 }