diff options
Diffstat (limited to 'nixpkgs/nixos/modules/misc/nixpkgs-flake.nix')
-rw-r--r-- | nixpkgs/nixos/modules/misc/nixpkgs-flake.nix | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/misc/nixpkgs-flake.nix b/nixpkgs/nixos/modules/misc/nixpkgs-flake.nix new file mode 100644 index 000000000000..8bfe05ca1994 --- /dev/null +++ b/nixpkgs/nixos/modules/misc/nixpkgs-flake.nix @@ -0,0 +1,105 @@ +{ config, options, lib, pkgs, ... }: + +with lib; + +let + cfg = config.nixpkgs.flake; +in +{ + options.nixpkgs.flake = { + source = mkOption { + # In newer Nix versions, particularly with lazy trees, outPath of + # flakes becomes a Nix-language path object. We deliberately allow this + # to gracefully come through the interface in discussion with @roberth. + # + # See: https://github.com/NixOS/nixpkgs/pull/278522#discussion_r1460292639 + type = types.nullOr (types.either types.str types.path); + + default = null; + defaultText = "if (using nixpkgsFlake.lib.nixosSystem) then self.outPath else null"; + + example = ''builtins.fetchTarball { name = "source"; sha256 = "${lib.fakeHash}"; url = "https://github.com/nixos/nixpkgs/archive/somecommit.tar.gz"; }''; + + description = mdDoc '' + The path to the nixpkgs sources used to build the system. This is automatically set up to be + the store path of the nixpkgs flake used to build the system if using + `nixpkgs.lib.nixosSystem`, and is otherwise null by default. + + This can also be optionally set if the NixOS system is not built with a flake but still uses + pinned sources: set this to the store path for the nixpkgs sources used to build the system, + as may be obtained by `builtins.fetchTarball`, for example. + + Note: the name of the store path must be "source" due to + <https://github.com/NixOS/nix/issues/7075>. + ''; + }; + + setNixPath = mkOption { + type = types.bool; + + default = cfg.source != null; + defaultText = "config.nixpkgs.flake.source != null"; + + description = mdDoc '' + Whether to set {env}`NIX_PATH` to include `nixpkgs=flake:nixpkgs` such that `<nixpkgs>` + lookups receive the version of nixpkgs that the system was built with, in concert with + {option}`nixpkgs.flake.setFlakeRegistry`. + + This is on by default for NixOS configurations built with flakes. + + This makes {command}`nix-build '<nixpkgs>' -A hello` work out of the box on flake systems. + + Note that this option makes the NixOS closure depend on the nixpkgs sources, which may add + undesired closure size if the system will not have any nix commands run on it. + ''; + }; + + setFlakeRegistry = mkOption { + type = types.bool; + + default = cfg.source != null; + defaultText = "config.nixpkgs.flake.source != null"; + + description = mdDoc '' + Whether to pin nixpkgs in the system-wide flake registry (`/etc/nix/registry.json`) to the + store path of the sources of nixpkgs used to build the NixOS system. + + This is on by default for NixOS configurations built with flakes. + + This option makes {command}`nix run nixpkgs#hello` reuse dependencies from the system, avoid + refetching nixpkgs, and have a consistent result every time. + + Note that this option makes the NixOS closure depend on the nixpkgs sources, which may add + undesired closure size if the system will not have any nix commands run on it. + ''; + }; + }; + + config = mkIf (cfg.source != null) (mkMerge [ + { + assertions = [ + { + assertion = cfg.setNixPath -> cfg.setFlakeRegistry; + message = '' + Setting `nixpkgs.flake.setNixPath` requires that `nixpkgs.flake.setFlakeRegistry` also + be set, since it is implemented in terms of indirection through the flake registry. + ''; + } + ]; + } + (mkIf cfg.setFlakeRegistry { + nix.registry.nixpkgs.to = mkDefault { + type = "path"; + path = cfg.source; + }; + }) + (mkIf cfg.setNixPath { + # N.B. This does not include nixos-config in NIX_PATH unlike modules/config/nix-channel.nix + # because we would need some kind of evil shim taking the *calling* flake's self path, + # perhaps, to ever make that work (in order to know where the Nix expr for the system came + # from and how to call it). + nix.nixPath = mkDefault ([ "nixpkgs=flake:nixpkgs" ] + ++ optional config.nix.channel.enable "/nix/var/nix/profiles/per-user/root/channels"); + }) + ]); +} |