Action_msgs not findable, because of relocation from /ros_ws/install/action_msgs/share/action_msgs/rust to /ros_ws/install/share/action_msgs/rust/

[Guelakais]

Since this error is relatively new, I wanted to show it. So colcon tries to find the action_msgs when building my package and searches incorrectly.

--- stderr: simple_ros_rs                                                                                                                                                                                             
error: failed to load source for dependency `action_msgs`

Caused by:
  Unable to update /ros_ws/install/action_msgs/share/action_msgs/rust

Caused by:
  failed to read `/ros_ws/install/action_msgs/share/action_msgs/rust/Cargo.toml`

Caused by:
  No such file or directory (os error 2)
---

As you can see, it looks for the library in the /ros_ws/install/action_msgs/share/action_msgs/rust path, where it can't find it. Actually, the library is in the path /ros_ws/install/share/action_msgs/rust/.
The comand, with whicht I'm building my packages is colcon build --continue-on-error --build-base /ros_ws/build --install-base /ros_ws/install --base-paths /ros_default /ros_ws /microros_ws --merge-install

[Guelakais]

So actually the colcon flag --merge-install makes the dependencies appear in install/share/ folder instead of directly in /install folder, which leads to confusion when building. If I see this correctly, the whole thing is rather a bug of cargo-ament-build than of colcon directly.

[esteve]

This is intended, Rust source files are installed into the share directory. Did you run this on a clean workspace or did you reuse an existing one?

[Guelakais]

That was a clean installation. I know now how the --merge-install flag works. I just didn't realise that -cargo-ament-build couldn't handle it.