Don't depend on external nixos-unstable channel

modules can now use unstablePkgs argument

nix-os/account.nix

@@ -1,9 +1,9 @@
-{ config, pkgs, ... }:
+{ config, pkgs, unstablePkgs, ... }:
 
-let
-  unstable = import <nixos-unstable> { config = config.nixpkgs.config; };
-in
 {
+  imports = [
+    ./unstable-packages.nix
+  ];
   users.users.wroclaw = {
     isNormalUser = true;
     description = "Rafał";
@@ -20,7 +20,7 @@ in
       firefox
       vivaldi
       discord-canary
-      unstable.vscode
+      unstablePkgs.vscode
     ];
   };
   users.groups.wroclaw.gid = 1000;

nix-os/desktop/gnome.nix

@@ -1,9 +1,9 @@
-{lib, config, pkgs, ...}:
+{lib, config, pkgs, unstablePkgs, ...}:
 
-let
-  unstable = import <nixos-unstable> {};
-in
 {
+  imports = [
+    ../unstable-packages.nix
+  ];
   config = rec {
     services.xserver.enable = true;
     services.xserver.desktopManager.gnome.enable = true;
@@ -207,7 +207,7 @@ in
       gnomeExtensions.tray-icons-reloaded
       gnomeExtensions.color-picker
       gnomeExtensions.top-bar-organizer
-      # unstable.gnomeExtensions.translate-indicator
+      # unstablePkgs.gnomeExtensions.translate-indicator
       # translate-shell
       pavucontrol
       #FIXME: Apply the cursor theme also in GTK3 config

nix-os/shell.nix

@@ -1,7 +1,6 @@
-{ config, pkgs, ... }:
+{ config, pkgs, unstablePkgs, ... }:
 
 let
-  unstable = import <nixos-unstable> {};
   rangerGit = pkgs.ranger.overrideAttrs (old: {
     version = "git";
     src = pkgs.fetchFromGitHub {
@@ -20,6 +19,9 @@ let
   });
 in
 {
+  imports = [
+    ./unstable-packages.nix
+  ];
   environment.systemPackages = with pkgs; [
     rangerGit
     kitty
@@ -50,7 +52,7 @@ in
     set vcs_aware true
     set show_hidden true
 
-    alias drag shell ${unstable.ripdrag}/bin/ripdrag -Axd %p &
+    alias drag shell ${unstablePkgs.ripdrag}/bin/ripdrag -Axd %p &
     map <C-d> drag
   '';
 

nix-os/unstable-packages.nix

@@ -0,0 +1,36 @@
+{config, pkgs, lib, ...}:
+
+let
+  nixos-unstable-exprs = builtins.fetchTarball https://channels.nixos.org/nixos-unstable/nixexprs.tar.xz;
+  nixos-unstable = import nixos-unstable-exprs {
+    inherit (config.nixpkgs) config localSystem crossSystem;
+    overlays = if config.unstable.usePkgsOverlays then config.pkgs.overlays else [];
+  };
+  nixos-unstable-version = builtins.concatStringsSep "." [
+    (builtins.readFile "${builtins.toString nixos-unstable-exprs}/.version")
+    (builtins.readFile "${builtins.toString nixos-unstable-exprs}/.version-suffix")
+  ];
+in
+{
+  options.unstable = {
+    enable = lib.mkEnableOption (lib.mkDoc ''
+      use of unstable packages in configuration. You can use `unstablePkgs` in configuration modules
+    '') // { default = true; };
+    usePkgsOverlays = lib.mkEnableOption (lib.mkDoc ''
+      use overlays from `nixpkgs.overlays`
+    '');
+    pkgs = lib.mkOption {
+      default = if config.unstable.enable then nixos-unstable else pkgs;
+      description = lib.mkDoc ''
+        acts like pkgs, but it has unstable packages if `unstable.enable` is enabled.
+        You can also use `unstablePkgs` in module arguments.
+      '';
+      visible = true;
+      readOnly = true;
+      type = lib.types.pkgs;
+    };
+  };
+  config._module.args.unstablePkgs = config.unstable.pkgs;
+  # FIXME: move it to the system derivation output (overrideAttrs config.system.build.toplevel?)
+  config.environment.etc."NIXOS-UNSTABLE-VERSION".text = nixos-unstable-version;
+}