From 43d32ac16d930f733041478bbcc1c7125a208664 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aleix=20Bon=C3=A9?= <aleix.boneribo@bsc.es>
Date: Fri, 28 Feb 2025 13:23:28 +0100
Subject: [PATCH] Use nixpkgs from flake.lock and support attrs when importing
 bscpkgs
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This makes `nix-build` and friends use the current flake lock instead of
the outdated pinned version we had in `./nixpkgs.nix`

With this, `nix-build -A ovni` and `nix build .#ovni` should produce the
same result.

This will fail if the flake nixpkgs input does not come from NixOS/nixpkgs.
We could use edolstra/flake-compat instead, but it's overkill imho.

Additionally, I made default.nix behave like nixpkgs, so that we can
import bscpkgs à la nixpkgs (Apply overlays and other options that nixpkgs
accepts):

```nix
let pkgs = import bscpkgs { inherit system; }; in <...>
```

Reviewed-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
---
 default.nix | 22 +++++++++++++++-------
 nixpkgs.nix |  9 ---------
 2 files changed, 15 insertions(+), 16 deletions(-)
 delete mode 100644 nixpkgs.nix

diff --git a/default.nix b/default.nix
index a28f7599..14c06c63 100644
--- a/default.nix
+++ b/default.nix
@@ -1,11 +1,19 @@
 let
   bscOverlay = import ./overlay.nix;
 
-  # Pin the nixpkgs
-  nixpkgsPath = import ./nixpkgs.nix;
-
-  pkgs = import nixpkgsPath {
-    overlays = [ bscOverlay ];
+  # read flake.lock and determine revision from there
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  inherit (lock.nodes.nixpkgs.locked) rev narHash;
+  fetchedNixpkgs = builtins.fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
+    sha256 = narHash;
   };
-
-in pkgs
+in
+{ overlays ? [ ]
+, nixpkgs ? fetchedNixpkgs
+, ...
+}@attrs:
+import nixpkgs (
+  (builtins.removeAttrs attrs [ "overlays" "nixpkgs" ]) //
+  { overlays = [ bscOverlay ] ++ overlays; }
+)
diff --git a/nixpkgs.nix b/nixpkgs.nix
deleted file mode 100644
index 20756970..00000000
--- a/nixpkgs.nix
+++ /dev/null
@@ -1,9 +0,0 @@
-let
-  commit = "e4ad989506ec7d71f7302cc3067abd82730a4beb";
-in builtins.fetchTarball {
-    # Descriptive name to make the store path easier to identify
-    name = "nixpkgs-${commit}";
-    url = "https://github.com/nixos/nixpkgs/archive/${commit}.tar.gz";
-    # Hash obtained using `nix-prefetch-url --unpack <url>`
-    sha256 = "sha256-de9KYi8rSJpqvBfNwscWdalIJXPo8NjdIZcEJum1mH0=";
-}