With clang-tidy-fix enabled we now can't use const shared pointers to const in subscription callbacks anymore (see https://travis-ci.com/github/ros-planning/moveit2/jobs/347903960#L809). Unfortunately, const references are not supported (ros2/rclcpp#281) so for now we basically have to pick one of the following options.

1. Disable linting for all callback functions and use callback(const Message::ConstSharedPtr msg)
2. callback(const Message::SharedPtr msg) errors because of const
3. callback(Message::ConstSharedPtr msg) errors because of const

I would opt for 2 since it's a rule that fits for all (also service callbacks and is closest to ROS 1 codebase) even though it's not really nice to have a non-const message access everywhere.

Update

So, apparently we need to disable clang-tidy rules to make this work. Do we want to do this on a case-by-case basis with // NOLINTNEXTLINE(performance-unnecessary-value-param) or project-wide? I would prefer keeping the rule enabled and keep an issue open to remove the lint ignores once const-ref callbacks are available. The only alternative we still have is to use fully non-const shared pointers, but I don't think we want to go that route.