Declare parameters uninitialized (ros2#1673)

* Declare parameters uninitialized

Fixes ros2#1649

Allow declaring parameters without an initial value or override.
This was possible prior to Galactic, but was made impossible since we started enforcing the types of parameters in Galactic.

Signed-off-by: Jacob Perron <[email protected]>

* Remove assertion

Signed-off-by: Jacob Perron <[email protected]>

* Throw NoParameterOverrideProvided exception if accessed before initialized

Signed-off-by: Jacob Perron <[email protected]>

* Add test getting static parameter after it is set

Signed-off-by: Jacob Perron <[email protected]>

* Do not throw on access of uninitialized dynamically typed parameter

Signed-off-by: Jacob Perron <[email protected]>

* Rename exception type

Signed-off-by: Jacob Perron <[email protected]>

* Remove unused exception type

Signed-off-by: Jacob Perron <[email protected]>

* Uncrustify

Signed-off-by: Jacob Perron <[email protected]>

Author: jacobperron

rclcpp/include/rclcpp/exceptions/exceptions.hpp

@@ -282,17 +282,17 @@ class ParameterModifiedInCallbackException : public std::runtime_error
   using std::runtime_error::runtime_error;
 };
 
-/// Thrown when a parameter override wasn't provided and one was required.
-class NoParameterOverrideProvided : public std::runtime_error
+/// Thrown when an uninitialized parameter is accessed.
+class ParameterUninitializedException : public std::runtime_error
 {
 public:
   /// Construct an instance.
   /**
    * \param[in] name the name of the parameter.
    * \param[in] message custom exception message.
    */
-  explicit NoParameterOverrideProvided(const std::string & name)
-  : std::runtime_error("parameter '" + name + "' requires an user provided parameter override")
+  explicit ParameterUninitializedException(const std::string & name)
+  : std::runtime_error("parameter '" + name + "' is not initialized")
   {}
 };
 

rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp

@@ -349,6 +349,21 @@ __declare_parameter_common(
     initial_value = &overrides_it->second;
   }
 
+  // If there is no initial value, then skip initialization
+  if (initial_value->get_type() == rclcpp::PARAMETER_NOT_SET) {
+    // Add declared parameters to storage (without a value)
+    parameter_infos[name].descriptor.name = name;
+    if (parameter_descriptor.dynamic_typing) {
+      parameter_infos[name].descriptor.type = rclcpp::PARAMETER_NOT_SET;
+    } else {
+      parameter_infos[name].descriptor.type = parameter_descriptor.type;
+    }
+    parameters_out[name] = parameter_infos.at(name);
+    rcl_interfaces::msg::SetParametersResult result;
+    result.successful = true;
+    return result;
+  }
+
   // Check with the user's callback to see if the initial value can be set.
   std::vector<rclcpp::Parameter> parameter_wrappers {rclcpp::Parameter(name, *initial_value)};
   // This function also takes care of default vs initial value.
@@ -413,14 +428,6 @@ declare_parameter_helper(
     parameter_descriptor.type = static_cast<uint8_t>(type);
   }
 
-  if (
-    rclcpp::PARAMETER_NOT_SET == default_value.get_type() &&
-    overrides.find(name) == overrides.end() &&
-    parameter_descriptor.dynamic_typing == false)
-  {
-    throw rclcpp::exceptions::NoParameterOverrideProvided(name);
-  }
-
   rcl_interfaces::msg::ParameterEvent parameter_event;
   auto result = __declare_parameter_common(
     name,
@@ -806,14 +813,21 @@ NodeParameters::get_parameters(const std::vector<std::string> & names) const
 rclcpp::Parameter
 NodeParameters::get_parameter(const std::string & name) const
 {
-  rclcpp::Parameter parameter;
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
 
-  if (get_parameter(name, parameter)) {
-    return parameter;
+  auto param_iter = parameters_.find(name);
+  if (
+    parameters_.end() != param_iter &&
+    (param_iter->second.value.get_type() != rclcpp::ParameterType::PARAMETER_NOT_SET ||
+    param_iter->second.descriptor.dynamic_typing))
+  {
+    return rclcpp::Parameter{name, param_iter->second.value};
   } else if (this->allow_undeclared_) {
-    return parameter;
-  } else {
+    return rclcpp::Parameter{};
+  } else if (parameters_.end() == param_iter) {
     throw rclcpp::exceptions::ParameterNotDeclaredException(name);
+  } else {
+    throw rclcpp::exceptions::ParameterUninitializedException(name);
   }
 }
 

rclcpp/test/rclcpp/test_node.cpp

@@ -335,9 +335,14 @@ TEST_F(TestNode, declare_parameter_with_no_initial_values) {
     rcl_interfaces::msg::ParameterDescriptor descriptor;
     descriptor.dynamic_typing = true;
     // no default, no initial
+    const std::string parameter_name = "parameter"_unq;
     rclcpp::ParameterValue value = node->declare_parameter(
-      "parameter"_unq, rclcpp::ParameterValue{}, descriptor);
+      parameter_name, rclcpp::ParameterValue{}, descriptor);
     EXPECT_EQ(value.get_type(), rclcpp::PARAMETER_NOT_SET);
+    // Does not throw if unset before access
+    EXPECT_EQ(
+      rclcpp::PARAMETER_NOT_SET,
+      node->get_parameter(parameter_name).get_parameter_value().get_type());
   }
   {
     // int default, no initial
@@ -2798,9 +2803,20 @@ TEST_F(TestNode, static_and_dynamic_typing) {
     EXPECT_EQ("hello!", param);
   }
   {
+    auto param = node->declare_parameter("integer_override_not_given", rclcpp::PARAMETER_INTEGER);
+    EXPECT_EQ(rclcpp::PARAMETER_NOT_SET, param.get_type());
+    // Throws if not set before access
     EXPECT_THROW(
-      node->declare_parameter("integer_override_not_given", rclcpp::PARAMETER_INTEGER),
-      rclcpp::exceptions::NoParameterOverrideProvided);
+      node->get_parameter("integer_override_not_given"),
+      rclcpp::exceptions::ParameterUninitializedException);
+  }
+  {
+    auto param = node->declare_parameter("integer_set_after_declare", rclcpp::PARAMETER_INTEGER);
+    EXPECT_EQ(rclcpp::PARAMETER_NOT_SET, param.get_type());
+    auto result = node->set_parameter(rclcpp::Parameter{"integer_set_after_declare", 44});
+    ASSERT_TRUE(result.successful) << result.reason;
+    auto get_param = node->get_parameter("integer_set_after_declare");
+    EXPECT_EQ(44, get_param.as_int());
   }
   {
     EXPECT_THROW(