add flake!

default.nix

@@ -0,0 +1,13 @@
+(import
+  (
+    let
+      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+    in
+    fetchTarball {
+      url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  {
+    src = ./.;
+  }).defaultNix

flake.lock

@@ -0,0 +1,60 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1641205782,
+        "narHash": "sha256-4jY7RCWUoZ9cKD8co0/4tFARpWB+57+r1bLLvXNJliY=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "b7547d3eed6f32d06102ead8991ec52ab0a4f1a7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1644151317,
+        "narHash": "sha256-TpXGBYCFKvEN7Q+To45rn4kqTbLPY4f56rF6ymUGGRE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "942b0817e898262cc6e3f0a5f706ce09d8f749f1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": "nixpkgs",
+        "utils": "utils"
+      }
+    },
+    "utils": {
+      "locked": {
+        "lastModified": 1644229661,
+        "narHash": "sha256-1YdnJAsNy69bpcjuoKdOYQX0YxZBiCYZo4Twxerqv7k=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "3cecb5b042f7f209c56ffd8371b2711a290ec797",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,72 @@
+{
+  description = "A tool for organising a music library";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    utils.url = "github:numtide/flake-utils";
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
+
+  outputs = { self, nixpkgs, utils, ... }:
+    {
+      overlay = final: prev:
+        let
+          system = final.system;
+          fold-to-ascii = final.python3Packages.callPackage ./nix-extra-deps/fold-to-ascii.nix { };
+        in {
+          fold-to-ascii = {fold-to-ascii = fold-to-ascii;};
+          musicutil = {
+            musicutil = final.python3Packages.buildPythonApplication rec {
+              pname = "musicutil";
+              version = "latest";
+
+              src = ./.;
+
+              postPatch = ''
+                substituteInPlace musicutil/meta.py --replace 'ffmpeg_path = "ffmpeg"' 'ffmpeg_path = "${final.ffmpeg}/bin/ffmpeg"'
+                substituteInPlace musicutil/meta.py --replace 'ffprobe_path = "ffprobe"' 'ffprobe_path = "${final.ffmpeg}/bin/ffprobe"'
+                substituteInPlace musicutil/meta.py --replace 'r128gain_path = "r128gain"' 'r128gain_path = "${final.r128gain}/bin/r128gain"'
+              '';
+
+              doCheck = false;
+
+              propagatedBuildInputs = with final.python3Packages; [
+                mutagen
+                fold-to-ascii
+                pyyaml
+              ];
+            };
+          };
+        };
+    } // utils.lib.eachSystem (utils.lib.defaultSystems) (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ self.overlay ];
+        };
+      in {
+        defaultPackage = self.packages."${system}".musicutil;
+        packages.musicutil = pkgs.musicutil.musicutil;
+
+        defaultApp = self.apps."${system}".musicutil;
+        apps.musicutil = {
+          type = "app";
+          program = "${self.defaultPackage."${system}"}/bin/musicutil";
+        };
+
+        devShell = pkgs.mkShell {
+          inputsFrom = [ self.packages.${system}.musicutil ];
+          buildInputs = with pkgs;
+            [
+              nixUnstable
+              mutagen
+              self.packages.${system}.fold-to-ascii
+              pyyaml
+            ];
+        };
+        lib = pkgs.musicutil.lib;
+      });
+}

result

@@ -0,0 +1 @@
+/nix/store/inz0v6slr3z7akjy6j7ds34rgxa08bnf-musicutil-latest

shell.nix

@@ -1,7 +0,0 @@
-{ pkgs ? import <nixpkgs> { } }:
-let
-  fold-to-ascii = (py: py.callPackage ./nix-extra-deps/fold-to-ascii.nix { });
-  my_python = pkgs.python39.withPackages
-    (py: with py; [ (fold-to-ascii py) py.mutagen py.autopep8 py.pyyaml ]);
-
-in pkgs.mkShell { packages = with pkgs; [ my_python ffmpeg fd r128gain ]; }