Merge pull request 'base: stabilize system.build.toplevel.outPath for vmVariant' (!105) from no-flake-in-vm into main

Reviewed-on: https://git.pvv.ntnu.no/Drift/pvv-nixos-config/pulls/105
Reviewed-by: Oystein Kristoffer Tveit <oysteikt@pvv.ntnu.no>

base/nix.nix

@@ -1,4 +1,4 @@
-{ inputs, ... }:
+{ lib, config, inputs, ... }:
 {
   nix = {
     gc = {
@@ -21,11 +21,16 @@
     ** use the same channel the system
     ** was built with
     */
-    registry = {
-      "nixpkgs".flake = inputs.nixpkgs;
-      "nixpkgs-unstable".flake = inputs.nixpkgs-unstable;
-      "pvv-nix".flake = inputs.self;
-    };
+    registry = lib.mkMerge [
+      {
+        "nixpkgs".flake = inputs.nixpkgs;
+        "nixpkgs-unstable".flake = inputs.nixpkgs-unstable;
+      }
+      # We avoid the reference to self in vmVariant to get a stable system .outPath for equivalence testing
+      (lib.mkIf (!config.virtualisation.isVmVariant) {
+        "pvv-nix".flake = inputs.self;
+      })
+    ];
     nixPath = [
       "nixpkgs=${inputs.nixpkgs}"
       "unstable=${inputs.nixpkgs-unstable}"

base/services/auto-upgrade.nix

@@ -1,4 +1,4 @@
-{ inputs, pkgs, lib, ... }:
+{ config, inputs, pkgs, lib, ... }:
 
 let
   inputUrls = lib.mapAttrs (input: value: value.url) (import "${inputs.self}/flake.nix").inputs;
@@ -26,12 +26,14 @@ in
 
   # workaround for https://github.com/NixOS/nix/issues/6895
   # via https://git.lix.systems/lix-project/lix/issues/400
-  environment.etc."current-system-flake-inputs.json".source
-    = pkgs.writers.writeJSON "flake-inputs.json" (
-      lib.flip lib.mapAttrs inputs (name: input:
-        # inputs.*.sourceInfo sans outPath, since writeJSON will otherwise serialize sourceInfo like a derivation
-        lib.removeAttrs (input.sourceInfo or {}) [ "outPath" ]
-          // { store-path = input.outPath; } # comment this line if you don't want to retain a store reference to the flake inputs
-      )
-    );
+  environment.etc = lib.mkIf (!config.virtualisation.isVmVariant) {
+    "current-system-flake-inputs.json".source
+      = pkgs.writers.writeJSON "flake-inputs.json" (
+        lib.flip lib.mapAttrs inputs (name: input:
+          # inputs.*.sourceInfo sans outPath, since writeJSON will otherwise serialize sourceInfo like a derivation
+          lib.removeAttrs (input.sourceInfo or {}) [ "outPath" ]
+            // { store-path = input.outPath; } # comment this line if you don't want to retain a store reference to the flake inputs
+        )
+      );
+  };
 }

flake.nix

@@ -169,9 +169,9 @@
     };
 
     devShells = forAllSystems (system: {
-      default = nixpkgs.legacyPackages.${system}.callPackage ./shell.nix { };
+      default = nixpkgs-unstable.legacyPackages.${system}.callPackage ./shell.nix { };
       cuda = let
-        cuda-pkgs = import nixpkgs {
+        cuda-pkgs = import nixpkgs-unstable {
           inherit system;
           config = {
             allowUnfree = true;