Specifying different package sets for packages within the same project

[newton-migosi]

I have a project with the following directory structure

my-app/
├─ frontend/
│  ├─ app/
│  │  ├─ Main.hs
│  ├─ frontend.cabal
├─ backend/
│  ├─ app/
│  │  ├─ Main.hs
│  ├─ backend.cabal
flake.nix

I'd like to build the subdirs frontend and backend using different package sets. How do I do this?

[newton-migosi]

The current version in the example only caters to using the default project.cabal https://github.com/srid/haskell-multi-nix/blob/c85563721c388629fa9e538a1d97274861bc8321/flake.nix

[newton-migosi]

It looks like the documentation is out of sync, comparing
https://zero-to-flakes.com/haskell-flake/modules/

{
  # Inside flake-parts' `perSystem`:
  haskellProjects.default = {
    imports = [
      inputs.common.haskellFlakeProjectModules.default
    ];
    packages = {
      myapp.root = ./.;
    };
  };
}

and
https://zero-to-flakes.com/haskell-flake/package-set

{
  haskellProjects.myproject = {
    packages.mypackage.source = ./.;

    basePackages = config.haskellProjects.ghc810.outputs.finalPackages;
  };
}

[srid]

The current version in the example only caters to using the default project.cabal https://github.com/srid/haskell-multi-nix/blob/c85563721c388629fa9e538a1d97274861bc8321/flake.nix

Local packages can be specified in the same manner as packages pointing to custom source paths: https://zero-to-flakes.com/haskell-flake/dependency#path

If you want them to use different package sets, you want to define distinct projects (because each project has its own package set and overrides):

haskellProjects.frontend-project = {
  packages = {
    frontend.source = ./frontend;
  };
};

haskellProjects.backend-project = {
  packages = {
    backend.source = ./backend;
  };
};

[newton-migosi]

thanks.. the library is changing pretty often (active development is good), I had missed out on the changes