nixosTests.xmonad: test configured recompilation

Add test coverage for the enableConfiguredRecompile option, checking
that we can compile and exec a new xmonad from a user's local config, as
well as restart the originally configured xmonad.

As I needed a reliable way to wait for recompilation to finish before
proceeding with subsequent test steps, I adjusted the startup behavior
to write a file ("oldXMonad" or "newXMonad") to /etc upon startup, and
replaced some "sleep" calls with "wait_for_file".

nixos/tests/xmonad.nix

@@ -1,4 +1,55 @@
-import ./make-test-python.nix ({ pkgs, ...} : {
+import ./make-test-python.nix ({ pkgs, ...}:
+
+let
+  mkConfig = name: keys: ''
+    import XMonad
+    import XMonad.Operations (restart)
+    import XMonad.Util.EZConfig
+    import XMonad.Util.SessionStart
+    import Control.Monad (when)
+    import Text.Printf (printf)
+    import System.Posix.Process (executeFile)
+    import System.Info (arch,os)
+    import System.Environment (getArgs)
+    import System.FilePath ((</>))
+
+    main = launch $ def { startupHook = startup } `additionalKeysP` myKeys
+
+    startup = isSessionStart >>= \sessInit ->
+      spawn "touch /tmp/${name}"
+        >> if sessInit then setSessionStarted else spawn "xterm"
+
+    myKeys = [${builtins.concatStringsSep ", " keys}]
+
+    compiledConfig = printf "xmonad-%s-%s" arch os
+
+    compileRestart resume =
+      whenX (recompile True) $
+        when resume writeStateToFile
+          *> catchIO
+            ( do
+                dir <- getXMonadDataDir
+                args <- getArgs
+                executeFile (dir </> compiledConfig) False args Nothing
+            )
+  '';
+
+  oldKeys =
+    [ ''("M-C-x", spawn "xterm")''
+      ''("M-q", restart "xmonad" True)''
+      ''("M-C-q", compileRestart True)''
+      ''("M-C-t", spawn "touch /tmp/somefile")'' # create somefile
+    ];
+
+  newKeys =
+    [ ''("M-C-x", spawn "xterm")''
+      ''("M-q", restart "xmonad" True)''
+      ''("M-C-q", compileRestart True)''
+      ''("M-C-r", spawn "rm /tmp/somefile")'' # delete somefile
+    ];
+
+  newConfig = pkgs.writeText "xmonad.hs" (mkConfig "newXMonad" newKeys);
+in {
   name = "xmonad";
   meta = with pkgs.lib.maintainers; {
     maintainers = [ nequissimus ];
@@ -10,21 +61,10 @@ import ./make-test-python.nix ({ pkgs, ...} : {
     services.xserver.displayManager.defaultSession = "none+xmonad";
     services.xserver.windowManager.xmonad = {
       enable = true;
+      enableConfiguredRecompile = true;
       enableContribAndExtras = true;
       extraPackages = with pkgs.haskellPackages; haskellPackages: [ xmobar ];
-      config = ''
-        import XMonad
-        import XMonad.Operations (restart)
-        import XMonad.Util.EZConfig
-        import XMonad.Util.SessionStart
-
-        main = launch $ def { startupHook = startup } `additionalKeysP` myKeys
-
-        startup = isSessionStart >>= \sessInit ->
-          if sessInit then setSessionStarted else spawn "xterm"
-
-        myKeys = [ ("M-C-x", spawn "xterm"), ("M-q", restart "xmonad" True) ]
-      '';
+      config = mkConfig "oldXMonad" oldKeys;
     };
   };
 
@@ -38,10 +78,40 @@ import ./make-test-python.nix ({ pkgs, ...} : {
     machine.wait_for_window("${user.name}.*machine")
     machine.sleep(1)
     machine.screenshot("terminal1")
+    machine.succeed("rm /tmp/oldXMonad")
     machine.send_key("alt-q")
-    machine.sleep(3)
+    machine.wait_for_file("/tmp/oldXMonad")
     machine.wait_for_window("${user.name}.*machine")
     machine.sleep(1)
     machine.screenshot("terminal2")
+
+    # /tmp/somefile should not exist yet
+    machine.fail("stat /tmp/somefile")
+
+    # original config has a keybinding that creates somefile
+    machine.send_key("alt-ctrl-t")
+    machine.sleep(1)
+    machine.succeed("stat /tmp/somefile")
+
+    # set up the new config
+    machine.succeed("mkdir -p ${user.home}/.xmonad")
+    machine.copy_from_host("${newConfig}", "${user.home}/.xmonad/xmonad.hs")
+
+    # recompile xmonad using the new config
+    machine.send_key("alt-ctrl-q")
+    machine.wait_for_file("/tmp/newXMonad")
+
+    # new config has a keybinding that deletes somefile
+    machine.send_key("alt-ctrl-r")
+    machine.sleep(1)
+    machine.fail("stat /tmp/somefile")
+
+    # restart with the old config, and confirm the old keybinding is back
+    machine.succeed("rm /tmp/oldXMonad")
+    machine.send_key("alt-q")
+    machine.wait_for_file("/tmp/oldXMonad")
+    machine.send_key("alt-ctrl-t")
+    machine.sleep(1)
+    machine.succeed("stat /tmp/somefile")
   '';
 })