Hopefully everything necessary is in the nix-shell. If not, feel free to modify nix-stuff and make it work.

Common things are kept in the justfile, for ease of execution. Just is in the nix-shell, if you don't have just and have Nix.

Formatting of Haskell should be done with stylish-haskell, which is in the nix-shell if you don't have it. This is the command I used: stylish-haskell --inplace -r app/*.hs

Formatting of the Cabal file can be done with cabal-fmt, which is also in the nix-shell. This is the command I used: cabal-fmt --inplace --indent 2 ./datatypetool.cabal

Formatting of Nix should be done with nixfmt, which is also in the nix-shell. This is the command I used: nixfmt shell.nix nix/*