{
  composerDependencies,
  lib,
  php83Packages,
  root,
  stdenvNoCC,
}:
let
  fs = lib.fileset;
  sourceFiles = fs.unions [
    (root + "/composer.json")
    (root + "/composer.lock")
  ];
  composerFiles = fs.toSource {
    fileset = sourceFiles;
    inherit root;
  };
in
stdenvNoCC.mkDerivation {
  name = "composer-dev-dependencies";
  src = composerFiles;
  nativeBuildInputs = [ php83Packages.composer ];
  buildPhase = ''
    cp -r ${composerDependencies}/vendor vendor
    chmod -R 755 vendor
    export COMPOSER_HOME=$TMPDIR
    composer install --no-interaction --no-scripts --no-ansi --no-autoloader
  '';
  installPhase = ''
    mkdir -p $out/
    cp -r vendor $out/
  '';
  dontFixup = true;
  outputHashAlgo = "sha256";
  outputHashMode = "recursive";
  outputHash = "sha256-oHkogPJiwXE+XBJxh0yTsFRYptLkgCG5v6ExFuef72Y=";
}

1. my-app -> would be made with buildComposerProject, using regular attributes. This is ready to go in prod if needed, it doesn't contain any require-dev stuff.

1. my-app-dev -> would also be made with buildComposerProject but this time, you can add an attribute that will install the require-dev dependencies.

In reply to @nebucatnetzer13:matrix.org
Okay, yeah that was my last idea as well, the problem with that is that the code for the project lands twice in the store right? It's not a killer, just a bit inelegant.

In reply to @rikudou:lemmings.world
Added php84 to https://history.nix-packages.com/search?packageName=php%2Ftag