Action message support #417
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| # `ros2_rust` Message Generation | ||
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| The `ros2_rust` project strives to maintain consistency with the upstream ROS 2 message generation | ||
| system. To this end, it provides two main packages: `rosidl_generator_rs` and `rosidl_runtime_rs`. | ||
| These packages provide the infrastructure required for defining and using ROS 2 messages, services, | ||
| and actions in Rust. | ||
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| At a high level, the `rosidl_generator_rs` package handles generation of interface crates from the | ||
| `.msg`, `.srv`, and `.action` files defined by a user. The `rosidl_runtime_rs` package provides | ||
| common functionality shared across message packages, such as support types and traits. Each of these | ||
| packages is described in more detail below. | ||
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| ## `rosidl_generator_rs` | ||
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| `rosidl_generator_rs` follows a very similar pattern to the other message generation packages for | ||
| ROS 2. To tie into this pipeline, it registers itself as a `"rosidl_generate_idl_interfaces"` | ||
| extension with `ament`. Doing so ensures that message packages calling `rosidl_generate_interfaces` | ||
| will invoke the Rust language generator in addition to any others. This is accomplished using the | ||
| various CMake scripts under the `cmake` directory. When this happens, the input interface files will | ||
| be converted into IDL files which, along with additional metadata, are fed into the `generate_rs` | ||
| function of `rosidl_generator_rs/__init__.py`. | ||
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| From here, the IDL files are parsed into an internal representation using the upstream | ||
| [`rosidl_parser`](https://github.com/ros2/rosidl/tree/rolling/rosidl_parser) package. This abstract | ||
| representation is then used to instantiate the various template files under the `resource` | ||
| subdirectory, producing a full Rust crate for each package. | ||
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| For each input message type, two `struct`s are generated: | ||
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| - An ergonomic representation of the message, using more idiomatic `std` types like `Vec` and | ||
| `String` for sequence and string fields. These are placed directly in the `msg` submodule of the | ||
| crate. | ||
| - A FFI-suitable `struct` that is ABI-compatible with the layout expected by the RMW layer. While | ||
| less ergonomic, these avoid the conversion overhead when passed to RMW. These `struct`s are placed | ||
| under the `msg::rmw` submodule. | ||
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| All the produced `struct`s implement the standard traits from `std` when possible, such as `Clone`, | ||
| `PartialEq`, and `Debug`. Additionally, when the generated crate's `serde` feature is enabled, these | ||
| structs implement the `Serialize` and `Deserialize` traits. | ||
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| ## `rosidl_runtime_rs` | ||
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| `rosidl_runtime_rs` is a runtime support package, providing `Message`, `Service`, and `Action` | ||
| traits that are implemented by the corresponding structs generated by `rosidl_generator_rs`. These | ||
| allow for generic interaction with these various interface types, both in client libraries like | ||
| `rclrs` and in user code. | ||
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| The package also provides a number of string and sequence types that are ABI-compatible with their | ||
| `rosidl_runtime_c` equivalents. This allows for more ergonomic use of the RMW-native message types. |
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| @{ | ||
| from rosidl_parser.definition import ( | ||
| ACTION_FEEDBACK_MESSAGE_SUFFIX, | ||
| ACTION_FEEDBACK_SUFFIX, | ||
| ACTION_GOAL_SERVICE_SUFFIX, | ||
| ACTION_GOAL_SUFFIX, | ||
| ACTION_RESULT_SERVICE_SUFFIX, | ||
| ACTION_RESULT_SUFFIX, | ||
| SERVICE_REQUEST_MESSAGE_SUFFIX, | ||
| SERVICE_RESPONSE_MESSAGE_SUFFIX, | ||
| ) | ||
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| action_msg_specs = [] | ||
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| for subfolder, action in action_specs: | ||
| action_msg_specs.append((subfolder, action.goal)) | ||
| action_msg_specs.append((subfolder, action.result)) | ||
| action_msg_specs.append((subfolder, action.feedback)) | ||
| action_msg_specs.append((subfolder, action.feedback_message)) | ||
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| action_srv_specs = [] | ||
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| for subfolder, action in action_specs: | ||
| action_srv_specs.append((subfolder, action.send_goal_service)) | ||
| action_srv_specs.append((subfolder, action.get_result_service)) | ||
| }@ | ||
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| pub mod rmw { | ||
| @{ | ||
| TEMPLATE( | ||
| 'msg_rmw.rs.em', | ||
| package_name=package_name, interface_path=interface_path, | ||
| msg_specs=action_msg_specs, | ||
| get_rs_name=get_rs_name, get_rmw_rs_type=get_rmw_rs_type, | ||
| pre_field_serde=pre_field_serde, | ||
| get_idiomatic_rs_type=get_idiomatic_rs_type, | ||
| constant_value_to_rs=constant_value_to_rs) | ||
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| TEMPLATE( | ||
| 'srv_rmw.rs.em', | ||
| package_name=package_name, interface_path=interface_path, | ||
| srv_specs=action_srv_specs, | ||
| get_rs_name=get_rs_name, get_rmw_rs_type=get_rmw_rs_type, | ||
| pre_field_serde=pre_field_serde, | ||
| get_idiomatic_rs_type=get_idiomatic_rs_type, | ||
| constant_value_to_rs=constant_value_to_rs) | ||
| }@ | ||
| } // mod rmw | ||
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| @{ | ||
| TEMPLATE( | ||
| 'msg_idiomatic.rs.em', | ||
| package_name=package_name, interface_path=interface_path, | ||
| msg_specs=action_msg_specs, | ||
| get_rs_name=get_rs_name, get_rmw_rs_type=get_rmw_rs_type, | ||
| pre_field_serde=pre_field_serde, | ||
| get_idiomatic_rs_type=get_idiomatic_rs_type, | ||
| constant_value_to_rs=constant_value_to_rs) | ||
| }@ | ||
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| @{ | ||
| TEMPLATE( | ||
| 'srv_idiomatic.rs.em', | ||
| package_name=package_name, interface_path=interface_path, | ||
| srv_specs=action_srv_specs, | ||
| get_rs_name=get_rs_name, get_rmw_rs_type=get_rmw_rs_type, | ||
| pre_field_serde=pre_field_serde, | ||
| get_idiomatic_rs_type=get_idiomatic_rs_type, | ||
| constant_value_to_rs=constant_value_to_rs) | ||
| }@ | ||
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| @[for subfolder, action_spec in action_specs] | ||
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| @{ | ||
| type_name = action_spec.namespaced_type.name | ||
| }@ | ||
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| #[link(name = "@(package_name)__rosidl_typesupport_c")] | ||
| extern "C" { | ||
| fn rosidl_typesupport_c__get_action_type_support_handle__@(package_name)__@(subfolder)__@(type_name)() -> *const std::ffi::c_void; | ||
| } | ||
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| // Corresponds to @(package_name)__@(subfolder)__@(type_name) | ||
| pub struct @(type_name); | ||
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| impl rosidl_runtime_rs::Action for @(type_name) { | ||
| type Goal = crate::@(subfolder)::@(type_name)@(ACTION_GOAL_SUFFIX); | ||
| type Result = crate::@(subfolder)::@(type_name)@(ACTION_RESULT_SUFFIX); | ||
| type Feedback = crate::@(subfolder)::@(type_name)@(ACTION_FEEDBACK_SUFFIX); | ||
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| fn get_type_support() -> *const std::ffi::c_void { | ||
| // SAFETY: No preconditions for this function. | ||
| unsafe { rosidl_typesupport_c__get_action_type_support_handle__@(package_name)__@(subfolder)__@(type_name)() } | ||
| } | ||
| } | ||
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| impl rosidl_runtime_rs::ActionImpl for @(type_name) { | ||
| type GoalStatusMessage = action_msgs::msg::rmw::GoalStatusArray; | ||
| type FeedbackMessage = crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_MESSAGE_SUFFIX); | ||
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| type SendGoalService = crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX); | ||
| type CancelGoalService = action_msgs::srv::rmw::CancelGoal; | ||
| type GetResultService = crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX); | ||
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| fn create_goal_request( | ||
| goal_id: &[u8; 16], | ||
| goal: crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SUFFIX), | ||
| ) -> crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX) { | ||
| crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX) { | ||
| goal_id: unique_identifier_msgs::msg::rmw::UUID { uuid: *goal_id }, | ||
|
There was a problem hiding this comment. I thought we didn't want to have a dependency on There was a problem hiding this comment. We want to avoid creating a dependency on However, the crates generated by the There was a problem hiding this comment. Ahh, I see. So the function signature of Yeah, we should explore some of the ideas discussed earlier to simplify this. Not needed for this PR though. |
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| goal, | ||
| } | ||
| } | ||
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| fn get_goal_request_uuid( | ||
| request: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX), | ||
| ) -> &[u8; 16] { | ||
| &request.goal_id.uuid | ||
| } | ||
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| fn create_goal_response( | ||
| accepted: bool, | ||
| stamp: (i32, u32), | ||
| ) -> crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX) { | ||
| crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX) { | ||
| accepted, | ||
| stamp: builtin_interfaces::msg::rmw::Time { | ||
| sec: stamp.0, | ||
| nanosec: stamp.1, | ||
| }, | ||
| } | ||
| } | ||
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| fn get_goal_response_accepted( | ||
| response: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX), | ||
| ) -> bool { | ||
| response.accepted | ||
| } | ||
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| fn get_goal_response_stamp( | ||
| response: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_GOAL_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX), | ||
| ) -> (i32, u32) { | ||
| (response.stamp.sec, response.stamp.nanosec) | ||
| } | ||
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| fn create_feedback_message( | ||
| goal_id: &[u8; 16], | ||
| feedback: crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_SUFFIX), | ||
| ) -> crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_MESSAGE_SUFFIX) { | ||
| let mut message = crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_MESSAGE_SUFFIX)::default(); | ||
| message.goal_id.uuid = *goal_id; | ||
| message.feedback = feedback; | ||
| message | ||
| } | ||
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| fn get_feedback_message_uuid( | ||
| feedback: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_MESSAGE_SUFFIX), | ||
| ) -> &[u8; 16] { | ||
| &feedback.goal_id.uuid | ||
| } | ||
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| fn get_feedback_message_feedback( | ||
| feedback: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_MESSAGE_SUFFIX), | ||
| ) -> &crate::@(subfolder)::rmw::@(type_name)@(ACTION_FEEDBACK_SUFFIX) { | ||
| &feedback.feedback | ||
| } | ||
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| fn create_result_request( | ||
| goal_id: &[u8; 16], | ||
| ) -> crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX) { | ||
| crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX) { | ||
| goal_id: unique_identifier_msgs::msg::rmw::UUID { uuid: *goal_id }, | ||
| } | ||
| } | ||
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| fn get_result_request_uuid( | ||
| request: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_REQUEST_MESSAGE_SUFFIX), | ||
| ) -> &[u8; 16] { | ||
| &request.goal_id.uuid | ||
| } | ||
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| fn create_result_response( | ||
| status: i8, | ||
| result: crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SUFFIX), | ||
| ) -> crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX) { | ||
| crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX) { | ||
| status, | ||
| result, | ||
| } | ||
| } | ||
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| fn get_result_response_result( | ||
| response: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX), | ||
| ) -> &crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SUFFIX) { | ||
| &response.result | ||
| } | ||
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| fn get_result_response_status( | ||
| response: &crate::@(subfolder)::rmw::@(type_name)@(ACTION_RESULT_SERVICE_SUFFIX)@(SERVICE_RESPONSE_MESSAGE_SUFFIX), | ||
| ) -> i8 { | ||
| response.status | ||
| } | ||
| } | ||
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| @[end for] | ||
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This is a little confusing to me. Looking at (what I believe to be) the impl for this typesupport function (link)
Why are we actually returning a void pointer here? This function is not marked as unsafe, but any handling of the return value may well need to use unsafe code. Could we not return a well formed type, such as
rosidl_service_type_support_t?This function seems to initialize the request and response members, but I don't actually see where those members are. The
@(type_name)struct appears empty. How is this working?There was a problem hiding this comment.
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c_void. However, doing so hasn't been necessary yet, and this is following the same pattern as the existingget_type_supportfunctions for messages and services. To make this happen, we would have to create a Rust binding for therosidl_{message,service,action}_type_support_tstructs, probably inrosidl_runtime_rs. I would be inclined to leave this for a separate PR to avoid growing the scope of this one.@(type_name)struct is empty since it's not really meant to be instantiated. It would only be used as a genericimpl Actionargument and to access the specificGoal,Feedback, andResultassociated message types.There was a problem hiding this comment.
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Sure, I'm fine leaving this to another PR. Just took a look at our usages (1) of this function historically and we do have
ascasts everywhere.ascasts can be problematic. So it would be nice to eventually not need this. However, maybe there is some other reason I'm missing as to why we returnvoid*here.I was referring to the data that function actually mutates in its implementation. I was misunderstanding and assumed that we actually held a handle to that data, but apparently we do not. It is a global variable managed by I guess the rosidl_runtime(?) that will be generated for each service.
This is outside the scope of this PR though. Just calling attention to it because we've been bitten by global variables we directly interact with via FFI before, see #386
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ascasts. I think the only thing preventing that would be defining the appropriate binding type in therosidl_runtime_rspackage. I can make an attempt at that in a follow-up PR.