Use mkDevShell for shell.nix

compat/fetch.nix

@@ -0,0 +1,17 @@
+let
+  inherit (builtins)
+    fetchTarball
+    fromJSON
+    readFile
+    ;
+  lockfile = fromJSON (readFile ../flake.lock);
+in
+input:
+let
+  locked = lockfile.nodes."${input}".locked;
+  inherit (locked) rev narHash owner repo;
+in
+fetchTarball {
+  url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+  sha256 = narHash;
+}

compat/nixpkgs.nix

@@ -0,0 +1,5 @@
+let
+  fetch = import ./fetch.nix;
+  nixpkgs = fetch "nixos";
+in
+nixpkgs

flake.nix

@@ -7,9 +7,10 @@
       nixos.url = "nixpkgs/release-20.09";
       home.url = "github:nix-community/home-manager/release-20.09";
       flake-utils.url = "github:numtide/flake-utils";
+      devshell.url = "github:numtide/devshell";
     };
 
-  outputs = inputs@{ self, home, nixos, master, flake-utils, nur }:
+  outputs = inputs@{ self, home, nixos, master, flake-utils, nur, devshell }:
     let
       inherit (builtins) attrNames attrValues readDir elem pathExists filter;
       inherit (flake-utils.lib) eachDefaultSystem mkApp;
@@ -23,7 +24,7 @@
 
       system = "x86_64-linux";
 
-      externOverlays = [ nur.overlay ];
+      externOverlays = [ nur.overlay devshell.overlay ];
       externModules = [ home.nixosModules.home-manager ];
 
       pkgset =
@@ -57,7 +58,7 @@
           pkgs' = pkgImport {
             pkgs = master;
             system = system';
-            overlays = [ ];
+            overlays = [ devshell.overlay ];
           };
 
           packages' = genPackages {
@@ -79,7 +80,6 @@
         {
           devShell = import ./shell.nix {
             pkgs = pkgs';
-            nixpkgs = nixos;
           };
 
           apps =

profiles/develop/zsh/default.nix

@@ -46,6 +46,7 @@ in
     systemPackages = with pkgs; [
       bat
       bzip2
+      devshell
       exa
       gitAndTools.hub
       gzip

shell.nix

@@ -1,7 +1,11 @@
 let
-  nixpkgs' = import ./nixpkgs-compat.nix;
+  nixpkgs = import ./compat/nixpkgs.nix;
+  fetch = import ./compat/fetch.nix;
+
+  devshell' = fetch "devshell";
+  pkgs' = import devshell' { inherit nixpkgs; };
 in
-{ pkgs ? import nixpkgs { }, nixpkgs ? nixpkgs' }:
+{ pkgs ? pkgs', ... }:
 let
   configs = "${toString ./.}#nixosConfigurations";
   build = "config.system.build";
@@ -22,29 +26,27 @@ let
       sudo nixos-rebuild --flake ".#$1" $@
     fi
   '';
+
+  nix = pkgs.writeShellScriptBin "nix" ''
+    ${pkgs.nixFlakes}/bin/nix --option experimental-features "nix-command flakes ca-references" "$@"
+  '';
 in
-pkgs.mkShell {
+pkgs.mkDevShell {
   name = "nixflk";
-  nativeBuildInputs = with pkgs; with installPkgs; [
+
+  packages = with pkgs; with installPkgs; [
     git
     git-crypt
     flk
-    nix-zsh-completions
+    nix
+    nixpkgs-fmt
     python38Packages.grip
     nixos-install
     nixos-generate-config
     nixos-enter
     nixos-rebuild
   ];
 
-  shellHook = ''
-    mkdir -p secrets
-    if ! nix flake show &> /dev/null; then
-      PATH=${
-        pkgs.writeShellScriptBin "nix" ''
-          ${pkgs.nixFlakes}/bin/nix --option experimental-features "nix-command flakes ca-references" "$@"
-        ''
-      }/bin:$PATH
-    fi
-  '';
+  env = { };
+
 }