X.U.NamedScratchpads: Fill NSPState when necessary

Since 3fc830aa09, scratchpads are now
added in namedScratchpadManageHook.  This, however, means that we need
some kind of MapRequestEvent to happen before processing scratchpads,
otherwise the manageHook didn't run yet and our extensible state is
being left empty.  When trying to open a scratchpad right after starting
xmonad—i.e., before having opened a window—this may not be the case.

Fixes: https://github.com/xmonad/xmonad-contrib/issues/728

XMonad/Util/NamedScratchpad.hs

@@ -131,9 +131,16 @@ instance ExtensionClass NSPState where
   initialValue :: NSPState
   initialValue = NSPState mempty
 
--- | Construct an 'NSPState' from an ordinary list of scratchpads.
-buildNSPState :: NamedScratchpads -> NSPState
-buildNSPState nsps = NSPState . Map.fromList $ zip (map name nsps) nsps
+-- | Try to fill the 'NSPState' with the given list of scratchpads.  In
+-- case the state is already non-empty, don't do anything and return
+-- that state.  Otherwise, fill the state with the given scratchpads.
+fillNSPState :: NamedScratchpads -> X NSPState
+fillNSPState nsps = do
+    nsp@(NSPState xs) <- XS.get
+    let nspState = NSPState . Map.fromList $ zip (map name nsps) nsps
+    if null xs
+        then nspState <$ XS.put nspState
+        else pure nsp
 
 -- | Manage hook that makes the window non-floating
 nonFloating :: ManageHook
@@ -160,7 +167,11 @@ runApplicationHere = spawnHere . cmd
 
 -- | Action to pop up specified named scratchpad
 --
--- NOTE: Ignores its first argument and uses 'NSPState' instead.
+-- Note [Ignored Arguments]: Most of the time, this function ignores its
+-- first argument and uses 'NSPState' instead.  The only time when it
+-- does not is when no other window has been opened before in the
+-- running xmonad instance.  If this is not your use-case, you can
+-- safely call this function with an empty list.
 namedScratchpadAction :: NamedScratchpads -- ^ Named scratchpads configuration
                       -> String           -- ^ Scratchpad name
                       -> X ()
@@ -168,7 +179,8 @@ namedScratchpadAction = customRunNamedScratchpadAction runApplication
 
 -- | Action to pop up specified named scratchpad, initially starting it on the current workspace.
 --
--- NOTE: Ignores its first argument and uses 'NSPState' instead.
+-- This function /almost always/ ignores its first argument; see Note
+-- [Ignored Arguments] for 'namedScratchpadAction'.
 spawnHereNamedScratchpadAction :: NamedScratchpads           -- ^ Named scratchpads configuration
                                -> String                     -- ^ Scratchpad name
                                -> X ()
@@ -176,7 +188,8 @@ spawnHereNamedScratchpadAction = customRunNamedScratchpadAction runApplicationHe
 
 -- | Action to pop up specified named scratchpad, given a custom way to initially start the application.
 --
--- NOTE: Ignores its second argument and uses 'NSPState' instead.
+-- This function /almost always/ ignores its second argument; see Note
+-- [Ignored Arguments] for 'namedScratchpadAction'.
 customRunNamedScratchpadAction :: (NamedScratchpad -> X ())  -- ^ Function initially running the application, given the configured @scratchpad@ cmd
                                -> NamedScratchpads           -- ^ Named scratchpads configuration
                                -> String                     -- ^ Scratchpad name
@@ -186,7 +199,8 @@ customRunNamedScratchpadAction = someNamedScratchpadAction (\f ws -> f $ NE.head
 -- | Like 'namedScratchpadAction', but execute the action for all
 -- scratchpads that match the query.
 --
--- NOTE: Ignores its first argument and uses 'NSPState' instead.
+-- This function /almost always/ ignores its first argument; see Note
+-- [Ignored Arguments] for 'namedScratchpadAction'.
 allNamedScratchpadAction :: NamedScratchpads
                          -> String
                          -> X ()
@@ -219,14 +233,15 @@ nsHideOnFocusLoss scratches = withWindowSet $ \winSet -> do
 
 -- | Execute some action on a named scratchpad.
 --
--- NOTE: Ignores its first argument and uses 'NSPState' instead.
+-- This function /almost always/ ignores its third argument; see Note
+-- [Ignored Arguments] for 'namedScratchpadAction'.
 someNamedScratchpadAction :: ((Window -> X ()) -> NE.NonEmpty Window -> X ())
                           -> (NamedScratchpad -> X ())
                           -> NamedScratchpads
                           -> String
                           -> X ()
 someNamedScratchpadAction f runApp _ns scratchpadName = do
-    NSPState scratchpadConfig <- XS.get
+    NSPState scratchpadConfig <- fillNSPState _ns  -- See Note [Filling NSPState]
     case scratchpadConfig !? scratchpadName of
         Just conf -> withWindowSet $ \winSet -> do
             let focusedWspWindows = maybe [] W.integrate (W.stack . W.workspace . W.current $ winSet)
@@ -244,6 +259,23 @@ someNamedScratchpadAction f runApp _ns scratchpadName = do
                 Just wins -> shiftToNSP (W.workspaces winSet) (`f` wins)
         Nothing -> return ()
 
+{- Note [Filling NSPState]
+
+We have to potentially populate the state with the given scratchpads
+here, in case the manageHook didn't run yet and it's still empty.
+
+For backwards compatibility, 3fc830aa09368dca04df24bf7ec4ac817f2de479
+introduced an internal state that's filled in the
+namedScratchpadManageHook.  A priori, this means that we would need some
+kind of MapRequestEvent to happen before processing scratchpads, since
+the manageHook doesn't run otherwise, leaving the extensible state empty
+until then.  When trying to open a scratchpad right after starting
+xmonad—i.e., before having opened a window—we thus have to populate the
+NSPState before looking for scratchpads.
+
+Related: https://github.com/xmonad/xmonad-contrib/issues/728
+-}
+
 -- | Tag of the scratchpad workspace
 scratchpadWorkspaceTag :: String
 scratchpadWorkspaceTag = "NSP"
@@ -252,10 +284,7 @@ scratchpadWorkspaceTag = "NSP"
 namedScratchpadManageHook :: NamedScratchpads -- ^ Named scratchpads configuration
                           -> ManageHook
 namedScratchpadManageHook nsps = do
-    ns <- liftX $ XS.get >>= \(NSPState xs) ->
-        if   null xs
-        then nsps <$ XS.put (buildNSPState nsps)
-        else pure $ Map.elems xs
+    ns <- Map.elems . coerce <$> liftX (fillNSPState nsps)
     composeAll $ fmap (\c -> query c --> hook c) ns
 
 -- | Shift some windows to the scratchpad workspace according to the