Deprecate the shared_ptr<MessageT> subscription callback signatures

[mini-1235]

Description

• Add static assert for removed subscription callback signatures

Fixes #2972

Is this user-facing behavior change?

Yes

Did you use Generative AI?

No

Additional Information

When working on this PR, I noticed that #1713 only deprecates MessageT. However, looking at the comment here:

rclcpp/rclcpp/include/rclcpp/any_subscription_callback.hpp

Lines 140 to 154 in eb49444

	// Deprecated signatures:
	using SharedPtrCallback =
	std::function<void (std::shared_ptr<SubscribedType>)>;
	using SharedPtrROSMessageCallback =
	std::function<void (std::shared_ptr<ROSMessageType>)>;
	using SharedPtrWithInfoCallback =
	std::function<void (std::shared_ptr<SubscribedType>, const rclcpp::MessageInfo &)>;
	using SharedPtrWithInfoROSMessageCallback =
	std::function<void (
	std::shared_ptr<ROSMessageType>,
	const rclcpp::MessageInfo &)>;
	using SharedPtrSerializedMessageCallback =
	std::function<void (std::shared_ptr<rclcpp::SerializedMessage>)>;
	using SharedPtrSerializedMessageWithInfoCallback =
	std::function<void (std::shared_ptr<rclcpp::SerializedMessage>, const rclcpp::MessageInfo &)>;

it looks like the type_adaptation/serialized message are not yet deprecated, how should we proceed?

In the meantime, I have also updated the tests for type_adaptation/serialized to use std::shared_ptr<const>

[mini-1235]

I have pulled and built the ROS2 repos from https://raw.githubusercontent.com/ros2/ros2/rolling/ros2.repos (Please let me know if there are any other repos I should include)

Removing std::shared_ptr<MessageT> would have an impact on:

• robot_state_publisher: Update subscription callback signatures ros/robot_state_publisher#241
• real_time_support: Update subscription callback signatures realtime_support#135 (example)
• message filter: Update subscription callback signatures message_filters#222 (test only)
• demos: Update subscription callback signatures demos#754

Removing/Deprecating std::shared_ptr<TypeAdapter/Serialize Message> would affect:

• demos: Update subscription callback signatures demos#754
• ros2 tracing: Update subscription callback signatures ros2_tracing#217 (test only)
• rosbag2 (examples and test): Update subscription callback signatures rosbag2#2225
• system test: Update subscription callback signatures system_tests#575

[fujitatomoya]

@mini-1235 thanks for fixing up all the related packages and repositories.

changing signatures are totally fine things to do including this PR, but i want to discuss with you on either we should enforcement or deprecation here for the next release.

[fujitatomoya]

It is true that those signatures have been deprecated for a long time as comment states, but my concern is that can we really enforce this all the sudden? i understand this is right thing to do, but this can possibly break the user space without any notification.

IMO, Deprecation Period should still be given for user space for next release, and then we can enforce the invalid signature assertion?

@mini-1235 @mjcarroll @ahcorde what do you think?

[mini-1235]

I think there are two points to discuss here:

1. std::shared_ptr<MessageT>: this was deprecated back in August 2021, but the deprecation warning was accidentally removed in February 2024. It looks like the majority of the ROS 2 core repositories are fine, but I am not entirely sure about other packages. For example, Nav2 still uses std::shared_ptr<MessageT> a lot: mini-1235/navigation2@9a6aca5

2. std::shared_ptr<TypeAdapter/Serialize Message>: this signature was actually never deprecated, so I think it should be deprecated instead of removed

In my current PR, I removed all forms of std::shared_ptr<> mainly for testing purposes. I am open to any suggestions on how this should be handled :)

[wjwwood]

Do you have a link to the commit that removed the deprecation?

We could re-deprecate it, just to be safe, and add the static asserts after a cycle.

I'm actually curious what the shared_ptr<T> does right now. I guess it must be taking a copy (e.g. as a unique_ptr<T>) and making a new shared_ptr<T> for each callback?

[mini-1235]

Do you have a link to the commit that removed the deprecation?

#2431

We could re-deprecate it, just to be safe, and add the static asserts after a cycle.

OK!

I'm actually curious what the shared_ptr does right now. I guess it must be taking a copy (e.g. as a unique_ptr) and making a new shared_ptr for each callback?

I haven't had time to look into the implementation deeply yet, so I can only speak based on the experiments I have run so far. With intra-process communication enabled, I am seeing that for n subscribers, there are n-1 copies made

[mini-1235]

I am not sure how to deal with the deprecated tests here

rclcpp/rclcpp/test/rclcpp/test_any_subscription_callback.cpp

Lines 683 to 723 in 1500449

	void shared_ptr_ta_free_func(std::shared_ptr<MyEmpty>) {}
	void shared_ptr_ta_w_info_free_func(
	std::shared_ptr<MyEmpty>, const rclcpp::MessageInfo &)
	{}
	INSTANTIATE_TEST_SUITE_P(
	SharedPtrCallbackTests,
	DispatchTestsWithTA,
	::testing::Values(
	// lambda
	InstanceContext<MyTA>{"lambda_ta", rclcpp::AnySubscriptionCallback<MyTA>().set(
	[](std::shared_ptr<MyEmpty>) {})},
	InstanceContext<MyTA>{"lambda_ta_with_info",
	rclcpp::AnySubscriptionCallback<MyTA>().set(
	[](std::shared_ptr<MyEmpty>, const rclcpp::MessageInfo &) {})},
	InstanceContext<MyTA>{"lambda", rclcpp::AnySubscriptionCallback<MyTA>().set(
	[](std::shared_ptr<test_msgs::msg::Empty>) {})},
	InstanceContext<MyTA>{"lambda_with_info",
	rclcpp::AnySubscriptionCallback<MyTA>().set(
	[](std::shared_ptr<test_msgs::msg::Empty>, const rclcpp::MessageInfo &) {})},
	// free function
	InstanceContext<MyTA>{"free_function_ta", rclcpp::AnySubscriptionCallback<MyTA>().set(
	shared_ptr_ta_free_func)},
	InstanceContext<MyTA>{"free_function_ta_with_info",
	rclcpp::AnySubscriptionCallback<MyTA>().set(
	shared_ptr_ta_w_info_free_func)},
	InstanceContext<MyTA>{"free_function", rclcpp::AnySubscriptionCallback<MyTA>().set(
	shared_ptr_free_func)},
	InstanceContext<MyTA>{"free_function_with_info",
	rclcpp::AnySubscriptionCallback<MyTA>().set(
	shared_ptr_w_info_free_func)},
	// bind function
	BindContext<MyTA, std::shared_ptr<MyEmpty>>("bind_method_ta"),
	BindContext<MyTA, std::shared_ptr<MyEmpty>, const rclcpp::MessageInfo &>(
	"bind_method_ta_with_info"),
	BindContext<MyTA, std::shared_ptr<test_msgs::msg::Empty>>("bind_method"),
	BindContext<MyTA, std::shared_ptr<test_msgs::msg::Empty>, const rclcpp::MessageInfo &>(
	"bind_method_with_info")
	),
	format_parameter_with_ta
	);

Should I add #define RCLCPP_AVOID_DEPRECATIONS_FOR_UNIT_TESTS 1 like the previous PR or any other better approach?