Install different gems in Docker container

I have a development environment that is used locally within docker containers, and deployed to a Heroku-like environment, which has a different setup than the local Docker setup. When running locally in Docker containers, I want to install debase and the ruby-debug-ide gems, so that I can use RubyMine locally, but these are not needed when deployed to the development instance. The deployment does not use the Docker / docker-compose files, so I'm okay with having them be local-development specific.

The trick I found was to use groups in the Gemfile.

In my Dockerfile, I'd call out the groups with the --with={groups} arguments:

RUN bundler install --with=development,docker