move build-tarball to a flake module

configuration.nix

@@ -5,10 +5,13 @@ let
   defaultUser = "nixos";
   automountPath = "/mnt";
   syschdemd = import ./syschdemd.nix { inherit lib pkgs config defaultUser; };
+  nixos-wsl = import ./default.nix;
 in
 {
-  imports = [
+  imports = with nixos-wsl.nixosModules; [
     "${modulesPath}/profiles/minimal.nix"
+
+    build-tarball
   ];
 
   # WSL is closer to a container than anything else
@@ -68,4 +71,5 @@ in
         ${pkgs.rsync}/bin/rsync -ar --delete $systemConfig/sw/share/$x/. /usr/share/$x
       done
     '';
+  };
 }

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

@@ -1,5 +1,21 @@
 {
   "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"
+      }
+    },
     "flake-utils": {
       "locked": {
         "lastModified": 1623875721,
@@ -32,6 +48,7 @@
     },
     "root": {
       "inputs": {
+        "flake-compat": "flake-compat",
         "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs"
       }

flake.nix

@@ -1,19 +1,30 @@
 {
   description = "NixOS WSL";
 
-  inputs.nixpkgs.url = "nixpkgs/nixos-20.09";
-  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-20.09";
+    flake-utils.url = "github:numtide/flake-utils";
+
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
 
   outputs = { self, nixpkgs, flake-utils, ... }:
     {
+      nixosModules = {
+        build-tarball = import ./modules/build-tarball.nix;
+      };
+
       nixosConfigurations.mysystem = nixpkgs.lib.nixosSystem {
         system = "x86_64-linux";
         modules = [
-          (import ./configuration.nix)
-          (import ./build-tarball.nix)
+          ./configuration.nix
         ];
         specialArgs = { inherit nixpkgs; };
       };
+
     } //
     flake-utils.lib.eachDefaultSystem (system:
       let

modules/build-tarball.nix

@@ -1,6 +1,5 @@
-{ config, pkgs, lib, nixpkgs ? <nixpkgs>, ... }:
-
-with lib;
+{ config, pkgs, lib, ... }:
+with builtins; with lib;
 let
   pkgs2storeContents = l: map (x: { object = x; symlink = "none"; }) l;
 
@@ -15,9 +14,9 @@ let
       if [ ! -e $out/nixos/nixpkgs ]; then
         ln -s . $out/nixos/nixpkgs
       fi
-      echo -n ${config.system.nixos.revision} > $out/nixos/.git-revision
-      echo -n ${config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
-      echo ${config.system.nixos.versionSuffix} | sed -e s/pre// > $out/nixos/svn-revision
+      echo -n ${toString config.system.nixos.revision} > $out/nixos/.git-revision
+      echo -n ${toString config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
+      echo ${toString config.system.nixos.versionSuffix} | sed -e s/pre// > $out/nixos/svn-revision
     '';
 
   preparer = pkgs.writeShellScriptBin "wsl-prepare" ''
@@ -49,16 +48,17 @@ let
 
     # Copy the system configuration
     mkdir -p ./etc/nixos
-    cp ${./configuration.nix} ./etc/nixos/configuration.nix
-    cp ${./syschdemd.nix} ./etc/nixos/syschdemd.nix
-    cp ${./syschdemd.sh} ./etc/nixos/syschdemd.sh
+    cp -R ${../.}/. ./etc/nixos/
   '';
+
 in
 {
   system.build.tarball = pkgs.callPackage "${nixpkgs}/nixos/lib/make-system-tarball.nix" {
     # No contents, structure will be added by prepare script
     contents = [ ];
 
+    fileName = "nixos-wsl-${config.system.nixos.release}-${pkgs.hostPlatform.system}";
+
     storeContents = pkgs2storeContents [
       config.system.build.toplevel
       channelSources

nixos.nix

@@ -2,12 +2,7 @@
 #   nix-build -A system -A config.system.build.tarball ./nixos.nix
 
 import <nixpkgs/nixos> {
-  configuration = {
-    imports = [
-      ./configuration.nix
-      ./build-tarball.nix
-    ];
-  };
+  configuration = import ./configuration.nix;
 
   system = "x86_64-linux";
 }