Why not go all the way? Have that in your aliases section of mix.exs:

      check: [
        "compile --warnings-as-errors",
        "format --check-formatted",
        "credo --strict",
        "coveralls.html",
        "dialyzer --format short"
      ]

Then just run mix check and voila, you almost have locally running CI.

For my Elixir, Rust, JavaScript, JSON and OCaml editing I use formatters even if I don’t like all of their decisions how things should look like.

Truth is, our code will be read by other people so I prefer to be a good citizen.

I love using the formatter, and specifically format on save in my editor, because it allows me to see if my code is right as it happens. If I save my file and everything snaps into place, I know I did things right. If it doesn’t, I know that I have a syntax error somewhere in the code I just wrote. Saves me from flicking back and forth to the server and my editor.