Switch from rcpputils::fs to std::filesystem

[christophebedard]

Part of ros2/rcpputils#164

I split the PR into two commits: internal changes and API changes.

[christophebedard]

I opened this as a draft because I'm not sure how to deal with the public API change for rclcpp::get_logging_directory(). I changed the return type from rcpputils::fs::path to std::filesystem::path because we can't have both, but they're functionally the same. I can't find any non-test calls to rclcpp::get_logging_directory() in the ROS 2 core.

The "cleanest" option is probably to deprecate the current function and create a new one with a different name, but that's unfortunate.

[fujitatomoya]

so your concern is, this breaks the followings, right? i mean basically we need to provide deprecation period for the user space, but we can not define both of the functions here.

// Compile Error Case-1
rcpputils::fs::path my_path = rclcpp::get_logging_directory();
// Compile Error Case-2
auto your_path = rclcpp::get_logging_directory();
bool directory_flag = your_path.is_directory(); // std::filesystem::path does not have this method.

just idea, i am not even sure if this is actually feasible.

• keep this function rclcpp as implemented, just change into std::filesystem:path.
• add copy constructor and copy assignment operator to rcpputils::fs::path to take std::filesystem::path.
• (as planned) add deprecation to rcpputils::fs::path, so that user can see that rcpputils::fs::path will be removed in next release?

again, this might not be doable idea...

I can't find any non-test calls to rclcpp::get_logging_directory() in the ROS 2 core.

the other part of me, asking myself if we need the deprecation period for this. but that is not something we cannot guarantee.

[mjcarroll]

I think that should work? It's a relatively cheap copy-constructor (basically string to string)

[christophebedard]

I'll give it a shot and will probably add a small test for it. I'm just wondering if it's too ambiguous if someone uses auto.

the other part of me, asking myself if we need the deprecation period for this. but that is not something we cannot guarantee.

Yeah it doesn't have a lot of users: https://github.com/search?q=rclcpp%3A%3Aget_logging_directory%28%29&type=code. Let's see if we can properly deprecate it first.

[christophebedard]

It might be too ambiguous, since both rcpputils::fs::path and std::filesystem::path have a conversion constructor for std::string.

[christophebedard]

Superseded by #2579