With No Flakes

Suppose you have a default.nix that looks like:

let
  sources = import ./npins;
in
{
  nixosConfigurations.my-laptop = ...; # use sources
}

First step is adding flake-like input definitions on it, or in a separate ./flake-file.nix file.

{
  flake-file.inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
  };
}

Boostraping using `./flake-file.nix`

And now, lets generate ./npins from ./flake-file.nix.

nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
  -A flake-file.sh --run write-npins --arg modules ./flake-file.nix

See also: all bootstrap command args

Run the same command whenever your input changes and they will be reflected into your pins.

Enabling Modular non-flakes.

Lets make use of Nix Modules in our non-flake.

First, create a ./modules directory and move our previous default.nix and flake-file.nix on it.

mkdir modules
mv flake-file.nix modules/inputs.nix
mv default.nix modules/default.nix

 { inputs, lib, ... }:
  let
   sources = import ./npins;
  in
  {
   imports = [ ./inputs.nix ];

   nixosConfigurations.my-laptop = ...; # use sources
   nixosConfigurations.my-laptop = ...; # use inputs
  }

Now create a new defualt.nix as follows:

let
  sources = import ./npins;
  nixpkgs = import sources.nixpkgs { };
  outputs = (nixpkgs.lib.evalModules {
    modules = ./modules;
    specialArgs = {
      inputs = sources; # (A) NOTE: Not flake-like inputs.
    };
  }).config;
in
outputs

To update npins from inputs at ./modules do:

nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
  -A flake-file.sh --run write-npins --arg modules ./modules

`(A)` flake-like inputs

If you wish to have flake-like resolved inputs to use flakes from non-flake world, take a look at with-inputs.nix used by templates/npins

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