An alias can't put arguments in the middle

In a Rails app that runs in Docker Compose, every rake task, migration and console goes through docker compose run web bundle exec .... In apps that don’t use Docker, it’s plain bundle exec. I type be for bundle exec all day, and I wanted it to decide for me. If the compose project is up, run the command in the web container. If not, run it on the host.

The first version was a one-line alias:

alias be="[ -n \"$(docker compose ls -q --filter name=$(basename $(pwd)))\" ] && docker compose run web bundle exec || bundle exec"

be rake db:migrate with the project running:

bundler: exec needs a command to run

An alias is text replacement. The shell pastes the alias in and puts your arguments after all of it, so the line becomes:

[ ... ] && docker compose run web bundle exec || bundle exec rake db:migrate

The docker branch gets no command at all. Only the last bundle exec sees rake db:migrate.

That alias had two more bugs. The $(...) parts sit inside double quotes, so they run once, when .zshrc loads, and never again. And A && B || C is not if/else. If the docker command fails, C runs as well, and the command runs a second time on the host.

A function fixes all three:

be() {
  if [ -n "$(docker compose ps --status running -q web 2>/dev/null)" ]; then
    docker compose run --rm web bundle exec "$@"
  else
    bundle exec "$@"
  fi
}

"$@" passes the arguments exactly as typed, quotes and spaces included. Since the check already knows the container is running, docker compose exec web would also work in place of run --rm, and it skips starting a new container.