Currently the action.rs template (here) makes use of the msg_idiomatic template at the top level module in the file. However, that template begins by importing (conditionally on a feature flag) serde::{Serialize, Deserialize} (here). If more than one msg is being added to the action.rs, that can result in a compilation error.

I've managed to get such an example while using mvukov/rules_ros2 with this library in a large project. I'll try to get a minimum reproducible example, but I suspect that import should be at the top level to avoid the chance of duplication.