From 5d2e4f01a5cc8b49c4a16372e8402598601ae0dc Mon Sep 17 00:00:00 2001
From: Konrad Malik <konrad.malik@gmail.com>
Date: Wed, 14 Aug 2024 12:27:20 +0200
Subject: [PATCH] fix: nix-path, registry

---
 hosts/common/modules/nix/not-hm.nix |  7 +++
 hosts/common/modules/nix/shared.nix | 72 +++++++++++++++--------------
 2 files changed, 45 insertions(+), 34 deletions(-)
 create mode 100644 hosts/common/modules/nix/not-hm.nix

diff --git a/hosts/common/modules/nix/not-hm.nix b/hosts/common/modules/nix/not-hm.nix
new file mode 100644
index 00000000..d1137077
--- /dev/null
+++ b/hosts/common/modules/nix/not-hm.nix
@@ -0,0 +1,7 @@
+{ inputs, ... }:
+{
+  # should be >= max-jobs
+  nix.nrBuildUsers = 16;
+  # Make `nix repl '<nixpkgs>'` use the same nixpkgs as the one used by this flake.
+  environment.etc."nix/inputs/nixpkgs".source = "${inputs.nixpkgs}";
+}
diff --git a/hosts/common/modules/nix/shared.nix b/hosts/common/modules/nix/shared.nix
index b3bda435..6eef2ec1 100644
--- a/hosts/common/modules/nix/shared.nix
+++ b/hosts/common/modules/nix/shared.nix
@@ -1,11 +1,15 @@
 {
-  config,
   pkgs,
   lib,
   inputs,
   ...
 }:
+let
+  isHomeManager = builtins.hasAttr "hm" lib;
+in
 {
+  imports = lib.optionals (!isHomeManager) [ ./not-hm.nix ];
+
   nixpkgs = {
     overlays = [
       (
@@ -25,38 +29,38 @@
       permittedInsecurePackages = [ ];
     };
   };
-  nix =
-    {
-      package = pkgs.nixVersions.latest;
-      settings = {
-        auto-optimise-store = lib.mkDefault true;
-        experimental-features = [
-          "nix-command"
-          "flakes"
-        ];
-        keep-derivations = true;
-        keep-outputs = true;
-        trusted-users =
-          [ "root" ]
-          ++ lib.optional pkgs.stdenvNoCC.isLinux "@wheel" ++ lib.optional pkgs.stdenvNoCC.isDarwin "@admin";
-        extra-substituters = [
-          "https://konradmalik.cachix.org"
-          "https://nix-community.cachix.org"
-        ];
-        extra-trusted-public-keys = [
-          "konradmalik.cachix.org-1:9REXmCYRwPNL0kAB0IMeTxnMB1Gl9VY5I8w7UVBTtSI="
-          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs"
-        ];
-        min-free = lib.mkDefault (10 * 1000 * 1000 * 1000); # 10gb
-        cores = lib.mkDefault 0;
-        max-jobs = lib.mkDefault "auto";
-      };
-    }
-    # below does not exist in plain home-manager
-    # but it will work for nixos config and for nix-darwin config
-    # this check is needed because of generic linux entry in homeConfigurations
-    // lib.optionalAttrs (builtins.hasAttr "nrBuildUsers" config.nix) {
-      # should be >= max-jobs
-      nrBuildUsers = 16;
+  nix = {
+    package = pkgs.nixVersions.latest;
+    # make `nix run nixpkgs#nixpkgs` use the same nixpkgs as the one used by this flake.
+    registry = {
+      nixpkgs.flake = inputs.nixpkgs;
+      nixpkgs-stable.flake = inputs.nixpkgs-stable;
     };
+    settings = {
+      # NIX_PATH is still used by many useful tools, so we set it to the same value as the one used by this flake.
+      # https://github.com/NixOS/nix/issues/9574
+      nix-path = lib.mkForce "nixpkgs=/etc/nix/inputs/nixpkgs";
+      auto-optimise-store = lib.mkDefault true;
+      experimental-features = [
+        "nix-command"
+        "flakes"
+      ];
+      keep-derivations = true;
+      keep-outputs = true;
+      trusted-users =
+        [ "root" ]
+        ++ lib.optional pkgs.stdenvNoCC.isLinux "@wheel" ++ lib.optional pkgs.stdenvNoCC.isDarwin "@admin";
+      extra-substituters = [
+        "https://konradmalik.cachix.org"
+        "https://nix-community.cachix.org"
+      ];
+      extra-trusted-public-keys = [
+        "konradmalik.cachix.org-1:9REXmCYRwPNL0kAB0IMeTxnMB1Gl9VY5I8w7UVBTtSI="
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs"
+      ];
+      min-free = lib.mkDefault (10 * 1000 * 1000 * 1000); # 10gb
+      cores = lib.mkDefault 0;
+      max-jobs = lib.mkDefault "auto";
+    };
+  };
 }