From 88f348a2c9d3593bc0b0aafaa5d73d7d56ac1f41 Mon Sep 17 00:00:00 2001
From: Wroclaw <wroclaw223@outlook.com>
Date: Mon, 17 Jun 2024 07:24:06 +0200
Subject: [PATCH] pkgs/overlays: create, move unstable there

also in unstable: use nixpkgs option to define
if unstable nixpkgs expressions should be from
nixos or nixpkgs channel
(default true, use nixos channel)
---
 nix-os/unstable-packages.nix | 37 ++++++++++--------------------------
 pkgs/overlays/unstable.nix   | 36 +++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 27 deletions(-)
 create mode 100644 pkgs/overlays/unstable.nix

diff --git a/nix-os/unstable-packages.nix b/nix-os/unstable-packages.nix
index 27e0727..4c41240 100644
--- a/nix-os/unstable-packages.nix
+++ b/nix-os/unstable-packages.nix
@@ -1,37 +1,20 @@
 {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")
-  ];
+  cfg = config.unstable;
+  unstableOverlay = import ../pkgs/overlays/unstable.nix;
 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;
-  config.system.extraSystemBuilderCmds = lib.mkIf config.unstable.enable ''
-    echo ${nixos-unstable-version} > $out/nixos-unstable-version
-  '';
-}
\ No newline at end of file
+  config = {
+    _module.args.unstablePkgs = if config.unstable.enable then pkgs.unstable else pkgs;
+    nixpkgs.overlays = lib.mkIf cfg.enable [ unstableOverlay ];
+    system.extraSystemBuilderCmds = lib.mkIf config.unstable.enable ''
+      echo ${pkgs.unstableVersion} > $out/nixos-unstable-version
+    '';
+  };
+}
diff --git a/pkgs/overlays/unstable.nix b/pkgs/overlays/unstable.nix
new file mode 100644
index 0000000..9aa8f2c
--- /dev/null
+++ b/pkgs/overlays/unstable.nix
@@ -0,0 +1,36 @@
+self: super:
+
+let
+  nixos = self.config.nixos or true;
+  useUnstable = self.config.useUnstable or true;
+
+  unstablePkgsExprs = if nixos
+    then builtins.fetchTarball "https://channels.nixos.org/nixos-unstable/nixexprs.tar.xz"
+    else builtins.fetchTarball "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
+  
+  # Compiled nixpkgs expression eg expressions from a nix channel
+  nixpkgsVersion = builtins.concatStringsSep "." [
+    (builtins.readFile "${unstablePkgsExprs}/.version")
+    (builtins.readFile "${unstablePkgsExprs}/.version-suffix")
+  ];
+
+  nixpkgsRevision = (builtins.readFile "${unstablePkgsExprs}/.git-revision");
+  unstablePkgsForNixpkgs = nixpkgs: import unstablePkgsExprs {
+    # localSystem -> pkgs.stdenv.hostPlatform or pkgs.stdenv.hostPlatform ???
+    localSystem = nixpkgs.stdenv.hostPlatform;
+    # crossSystem -> nixpkgs.stdenv.targetPlatform
+    crossSystem = nixpkgs.stdenv.targetPlatform;
+    # config -> pkgs.config
+    config = nixpkgs.config;
+    # overlays -> partial of pkgs.overlays
+    overlays = nixpkgs.overlays;
+    # crossOverlays -> partial of pkgs.overlays
+    # crossOverlays are merged to overlays, not sure what issues that might raise.
+    # ignoring.
+  };
+in
+{
+  unstable = if useUnstable then unstablePkgsForNixpkgs self else self;
+  unstableVersion = self.lib.optionalString useUnstable nixpkgsVersion;
+  unstableRevision = self.lib.optionalString useUnstable nixpkgsRevision;
+}