Requesting explanation of flag in project-development.rst

[jerbaroo]

nix-shell -A shells.ghcjs --run "cabal --project-file=cabal-ghcjs.project --builddir=dist-ghcjs new-build all"

Would the following be a shorter alternative?

nix-shell -A shells.ghcjs --run "cabal --builddir=dist-ghcjs new-build frontend"

My guess is the cabal-ghcjs.project file is passed to ensure that the backend package is not compiled. However passing the package frontend should be enough since backend is not a dependency and neither is is specified in shelld.ghcjs.

Does passing shells.ghcjs not specify that GHCJS should be used to compile? Or what is the purpose of using that shell over shells.ghc in this case?

Thanks you!