From 0dfac33429194a9713a38891aeacab68cc6084ab Mon Sep 17 00:00:00 2001
From: Felix Stupp <felix.stupp@banananet.work>
Date: Sun, 25 Aug 2024 20:48:08 +0000
Subject: [PATCH] extract & rework backports overlay

---
 flake.nix                     |  2 ++
 nix/nixos-modules/default.nix |  9 +--------
 nix/overlays/backports.nix    | 20 ++++++++++++++++++++
 nix/overlays/default.nix      | 14 ++++++++++++++
 4 files changed, 37 insertions(+), 8 deletions(-)
 create mode 100644 nix/overlays/backports.nix
 create mode 100644 nix/overlays/default.nix

diff --git a/flake.nix b/flake.nix
index 02c6b1d..b6e0d14 100644
--- a/flake.nix
+++ b/flake.nix
@@ -100,6 +100,8 @@
 
       nixosModules = importFlakeMod ./nix/nixos-modules;
 
+      overlays = importFlakeMod ./nix/overlays;
+
       packages = importFlakeModWithSystem ./nix/packages;
 
     };
diff --git a/nix/nixos-modules/default.nix b/nix/nixos-modules/default.nix
index 0442f49..85ac52d 100644
--- a/nix/nixos-modules/default.nix
+++ b/nix/nixos-modules/default.nix
@@ -49,14 +49,7 @@
         outputs.nixosModules.banananetwork
       ];
       config = {
-        nixpkgs.overlays = [
-          # TODO until 24.11
-          (lib.mkIf (!lib.versionAtLeast lib.version "24.11") (
-            final: prev: {
-              inherit ((lib.systemSpecificVars pkgs.system).pkgs_unstable) nixfmt-rfc-style wcurl;
-            }
-          ))
-        ];
+        nixpkgs.overlays = lib.singleton outputs.overlays.backports;
       };
     };
 
diff --git a/nix/overlays/backports.nix b/nix/overlays/backports.nix
new file mode 100644
index 0000000..3821df3
--- /dev/null
+++ b/nix/overlays/backports.nix
@@ -0,0 +1,20 @@
+{ lib, ... }@flakeArg:
+{ pkgs_unstable, ... }@systemArg:
+final: prev:
+let
+  list = [
+    # TODO until 24.11
+    "nixfmt-rfc-style"
+    "wcurl"
+  ];
+  backport =
+    pkgAttrName:
+    let
+      alreadyStable = builtins.hasAttr pkgAttrName prev;
+      stableSource = lib.warn "consider removing ${pkgAttrName} from backports list as it is now available on stable" prev;
+      source = if alreadyStable then stableSource else pkgs_unstable;
+      pkg = builtins.getAttr pkgAttrName source;
+    in
+    pkg;
+in
+lib.genAttrs list backport
diff --git a/nix/overlays/default.nix b/nix/overlays/default.nix
new file mode 100644
index 0000000..76f0c08
--- /dev/null
+++ b/nix/overlays/default.nix
@@ -0,0 +1,14 @@
+{ lib, ... }@flakeArg:
+let
+  inherit (lib) systemSpecificVars;
+  rawImport = path: import path flakeArg;
+  wrapOverlay =
+    overlay: final: prev:
+    overlay (systemSpecificVars prev.system) final prev;
+  importOverlay = path: wrapOverlay (rawImport path);
+in
+{
+
+  backports = importOverlay ./backports.nix;
+
+}