nixos/etc.nix: Make independent

(cherry picked from commit 56c283e5c8dfd4d8d5daa15dfa3896beef2ac012)

nixos/modules/module-list.nix

···
   ./system/boot/systemd-nspawn.nix
   ./system/boot/timesyncd.nix
   ./system/boot/tmp.nix
-  ./system/etc/etc.nix
+  ./system/etc/etc-activation.nix
   ./tasks/auto-upgrade.nix
   ./tasks/bcache.nix
   ./tasks/cpu-freq.nix

nixos/modules/system/etc/etc-activation.nix

···
+{ config, lib, ... }:
+let
+  inherit (lib) stringAfter;
+in {
+
+  imports = [ ./etc.nix ];
+
+  config = {
+    system.activationScripts.etc =
+      stringAfter [ "users" "groups" ] config.system.build.etcActivationCommands;
+  };
+}

nixos/modules/system/etc/etc.nix

···
 
 {
 
+  imports = [ ../build.nix ];
+
   ###### interface
 
   options = {
···
   config = {
 
     system.build.etc = etc;
-
-    system.activationScripts.etc = stringAfter [ "users" "groups" ]
+    system.build.etcActivationCommands =
       ''
         # Set up the statically computed bits of /etc.
         echo "setting up /etc..."
         ${pkgs.perl.withPackages (p: [ p.FileSlurp ])}/bin/perl ${./setup-etc.pl} ${etc}/etc
       '';
-
   };
 
 }

nixos/modules/system/etc/test.nix

···
+{ lib
+, coreutils
+, fakechroot
+, fakeroot
+, evalMinimalConfig
+, pkgsModule
+, runCommand
+, util-linux
+, vmTools
+, writeText
+}:
+let
+  node = evalMinimalConfig ({ config, ... }: {
+    imports = [ pkgsModule ../etc/etc.nix ];
+    environment.etc."passwd" = {
+      text = passwdText;
+    };
+    environment.etc."hosts" = {
+      text = hostsText;
+      mode = "0751";
+    };
+  });
+  passwdText = ''
+    root:x:0:0:System administrator:/root:/run/current-system/sw/bin/bash
+  '';
+  hostsText = ''
+    127.0.0.1 localhost
+    ::1 localhost
+    # testing...
+  '';
+in
+lib.recurseIntoAttrs {
+  test-etc-vm =
+    vmTools.runInLinuxVM (runCommand "test-etc-vm" { } ''
+      mkdir -p /etc
+      ${node.config.system.build.etcActivationCommands}
+      set -x
+      [[ -L /etc/passwd ]]
+      diff /etc/passwd ${writeText "expected-passwd" passwdText}
+      [[ 751 = $(stat --format %a /etc/hosts) ]]
+      diff /etc/hosts ${writeText "expected-hosts" hostsText}
+      set +x
+      touch $out
+    '');
+
+  # fakeroot is behaving weird
+  test-etc-fakeroot =
+    runCommand "test-etc"
+      {
+        nativeBuildInputs = [
+          fakeroot
+          fakechroot
+          # for chroot
+          coreutils
+          # fakechroot needs getopt, which is provided by util-linux
+          util-linux
+        ];
+        fakeRootCommands = ''
+          mkdir -p /etc
+          ${node.config.system.build.etcActivationCommands}
+          diff /etc/hosts ${writeText "expected-hosts" hostsText}
+          touch $out
+        '';
+      } ''
+      mkdir fake-root
+      export FAKECHROOT_EXCLUDE_PATH=/dev:/proc:/sys:${builtins.storeDir}:$out
+      fakechroot fakeroot chroot $PWD/fake-root bash -c 'source $stdenv/setup; eval "$fakeRootCommands"'
+    '';
+
+}

nixos/tests/all-tests.nix

···
   env = handleTest ./env.nix {};
   ergo = handleTest ./ergo.nix {};
   ergochat = handleTest ./ergochat.nix {};
+  etc = pkgs.callPackage ../modules/system/etc/test.nix { inherit evalMinimalConfig; };
   etcd = handleTestOn ["x86_64-linux"] ./etcd.nix {};
   etcd-cluster = handleTestOn ["x86_64-linux"] ./etcd-cluster.nix {};
   etebase-server = handleTest ./etebase-server.nix {};