Flake from the Template fails to build

[mirosval]

Describe the issue

When I start a new project using the Flake Template, I get error: attribute 'legacyPackages' missing.

❯ nix build
warning: Git tree '/Users/mirosval/work/tests/poetry' is dirty
warning: creating lock file '/Users/mirosval/work/tests/poetry/flake.lock'
warning: Git tree '/Users/mirosval/work/tests/poetry' is dirty
error:
       … while evaluating the attribute 'packages.aarch64-darwin.myapp'

         at /nix/store/r04lcfxjaqj6v96fjzd9l053fw8yn4zm-source/flake.nix:22:11:

           21|         packages = {
           22|           myapp = mkPoetryApplication { projectDir = self; };
             |           ^
           23|           default = self.packages.${system}.myapp;

       error: attribute 'legacyPackages' missing

       at /nix/store/r04lcfxjaqj6v96fjzd9l053fw8yn4zm-source/flake.nix:17:18:

           16|         # see https://github.com/nix-community/poetry2nix/tree/master#api for more functions and examples.
           17|         inherit (poetry2nix.legacyPackages.${system}) mkPoetryApplication;
             |                  ^
           18|         pkgs = nixpkgs.legacyPackages.${system};

Additional context

I'm trying to integrate poetry2nix into a flake-based project but can't figure out where to find mkPoetryApplication given

    poetry2nix = {
      url = "github:nix-community/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

in the inputs and the only example in this repo that I was able to find is the template, which is also broken it seems.

[cpcloud]

Thanks for the issue!

I've put up #1368 to fix this, and I've added a test to catch future regressions.