Implement standardized "use flags" for Nixpkgs

pkgs/top-level/options.nix

@@ -0,0 +1,154 @@
+{lib, hostPlatform}:
+
+with lib;
+
+# Define some user flags. Each one will be passed as an argument to
+# callPackage and can be used directly by packages to configure
+# themselves. Note that none of these should be mutually exclusive.
+# For instance enabling X11 should not imply that Wayland is disabled.
+
+{
+
+  lang = mkOption {
+    default = "en";
+    type = types.string;
+    description = ''
+
+      The target language to compile packages with support for.
+
+    '';
+  };
+
+  withX11 = mkOption {
+    default = hostPlatform.isLinux; # also BSDs?
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the X Window System.
+
+    '';
+  };
+
+  withWayland = mkOption {
+    default = hostPlatform.isLinux; # also BSDs?
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the Wayland window system.
+
+    '';
+  };
+
+  withAlsa = mkOption {
+    default = hostPlatform.isLinux;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the ALSA sound system.
+
+    '';
+  };
+
+  withPulseAudio = mkOption {
+    default = hostPlatform.isLinux;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the PulseAudio sound system.
+
+    '';
+  };
+
+  withJack = mkOption {
+    default = false;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the JACK sound system
+
+    '';
+  };
+
+  withQt = mkOption {
+    default = true;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the Qt graphical toolkit
+
+    '';
+  };
+
+  withGtk = mkOption {
+    default = false;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the GTK graphical toolkit
+
+    '';
+  };
+
+  withApple = mkOption {
+    default = hostPlatform.isDarwin;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with Apple's proprietary frameworks.
+
+      Note that this only supports macOS currently.
+
+    '';
+  };
+
+  withSystemd = mkOption {
+    default = hostPlatform.isLinux;
+    type = types.bool;
+    description = ''
+
+      Whether to compile packages with support for the Systemd init system.
+
+      Note that this specifically means compiling packages with the
+      /Systemd/ libraries. Unit files should always be included in
+      packages.
+
+    '';
+  };
+
+  allowUnfree = mkOption {
+    default = false;
+    type = types.bool;
+    description = ''
+
+      Whether to support unfree software. This includes everything not
+      considered free software by the Free Software Foundation.
+
+    '';
+  };
+
+  enableShared = mkOption {
+    default = true;
+    type = types.bool;
+    description = ''
+
+      Whether to build packages with shared linking. This has
+      historically been the default everywhere in Nixpkgs.
+
+    '';
+  };
+
+  enableStatic = mkOption {
+    default = targetPlatform.isiOS;
+    type = types.bool;
+    description = ''
+
+      Whether to build packages with static linking if available. Note
+      that not all packages support this.
+
+      Packages using this option may or may not also build shared
+      libraries. Set enableShare to disable those.
+
+    '';
+  };
+
+}

pkgs/top-level/release-options.nix

@@ -0,0 +1,45 @@
+{ pkgs ? import ../..
+, lib ? import ../../lib }:
+
+lib.mapAttrs (n: v: pkgs v) {
+  headlessLinux = {
+    config = {
+      withGtk = false;
+      withQt = false;
+      withPulseAudio = false;
+      withJack = false;
+      withAlsa = false;
+      withWayland = false;
+      withX11 = false;
+    };
+    localSystem = { system = "x86_64-linux"; };
+  };
+  freeDarwin = {
+    config = {
+      withApple = false;
+      allowUnfree = false;
+    };
+    localSystem = { system = "x86_64-darwin"; };
+  };
+  slnosLinux = {
+    config = {
+      withSystemd = false;
+      withPulseAudio = false;
+    };
+    localSystem = { system = "x86_64-linux"; };
+  };
+  staticLinux = {
+    config = {
+      enableStatic = true;
+      enableShared = false;
+    };
+    localSystem = { system = "x86_64-linux"; };
+  };
+  staticDarwin = {
+    config = {
+      enableStatic = true;
+      enableShared = false;
+    };
+    localSystem = { system = "x86_64-darwin"; };
+  };
+}

pkgs/top-level/splice.nix

@@ -36,7 +36,13 @@ let
   # whether `nativeDrv` or `crossDrv` is the default in `defaultScope`.
   pkgsWithoutFetchers = lib.filterAttrs (n: _: !lib.hasPrefix "fetch" n) pkgs;
   targetPkgsWithoutFetchers = lib.filterAttrs (n: _: !lib.hasPrefix "fetch" n) pkgs.targetPackages;
-  defaultHostTargetScope = pkgsWithoutFetchers // pkgs.xorg;
+
+  # Allow users to specify global use flags that are applied in all
+  # packages.
+  options = lib.mapAttrs (name: option: pkgs.config.${name} or option.default)
+              (import ./options.nix { inherit lib; inherit (pkgs) hostPlatform; });
+
+  defaultHostTargetScope = pkgsWithoutFetchers // pkgs.xorg // options;
   defaultTargetTargetScope = targetPkgsWithoutFetchers // targetPkgsWithoutFetchers.xorg or {};
 
   splicer = pkgsBuildBuild: pkgsBuildHost: pkgsBuildTarget: