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Setting start_type_description_service param can fail when automatically_declare_parameters_from_overrides is true #2892

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#2897
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Setting start_type_description_service param can fail when automatically_declare_parameters_from_overrides is true#2892
#2897
@roncapat

Description

@roncapat
roncapat
opened on Jul 7, 2025

This is the code that declares the parameter start_type_description_service.

It uses a try/catch idiom, but does not catches ParameterAlreadyDeclaredException.

rclcpp/rclcpp/src/rclcpp/node_interfaces/node_type_descriptions.cpp

Lines 70 to 84 in 7ebc9e4

bool enabled = false;
try {
auto enable_param = node_parameters->declare_parameter(
enable_param_name,
rclcpp::ParameterValue(true),
rcl_interfaces::msg::ParameterDescriptor()
.set__name(enable_param_name)
.set__type(rclcpp::PARAMETER_BOOL)
.set__description("Start the ~/get_type_description service for this node.")
.set__read_only(true));
enabled = enable_param.get<bool>();
} catch (const rclcpp::exceptions::InvalidParameterTypeException & exc) {
RCLCPP_ERROR(logger_, "%s", exc.what());
throw;
}

Notice how use_sim_time is declared instead:

rclcpp/rclcpp/src/rclcpp/time_source.cpp

Lines 254 to 274 in 7ebc9e4

rclcpp::ParameterValue use_sim_time_param;
const std::string use_sim_time_name = "use_sim_time";
if (!node_parameters_->has_parameter(use_sim_time_name)) {
use_sim_time_param = node_parameters_->declare_parameter(
use_sim_time_name,
rclcpp::ParameterValue(false));
} else {
use_sim_time_param = node_parameters_->get_parameter(use_sim_time_name).get_parameter_value();
}
if (use_sim_time_param.get_type() == rclcpp::PARAMETER_BOOL) {
if (use_sim_time_param.get<bool>()) {
parameter_state_ = SET_TRUE;
clocks_state_.enable_ros_time();
create_clock_sub();
}
} else {
RCLCPP_ERROR(
logger_, "Invalid type '%s' for parameter 'use_sim_time', should be 'bool'",
rclcpp::to_string(use_sim_time_param.get_type()).c_str());
throw std::invalid_argument("Invalid type for parameter 'use_sim_time', should be 'bool'");
}

While use_sim_time is checked with has_parameter() call for existence, start_type_description_service declaration does not.

I believe this is a bug and should be fixed. If maintainers agree, I can open a PR.

BTW, I strongly believe that this kind of "standard node parameters" should share an almost identical way of declaring them, for code commonality.

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