Move over a few more commands.

server/Scion/Server/Commands2.hs

@@ -1,6 +1,11 @@
 {-# LANGUAGE OverloadedStrings, ExistentialQuantification #-}
 {-# LANGUAGE ScopedTypeVariables, PatternGuards #-}
-module Scion.Server.Commands2 where
+{-# OPTIONS_GHC -fwarn-unused-binds -fwarn-unused-imports #-}
+-- Warn unused binds is important, because it allows us to notice when
+-- we forgot to add a command to 'allCommands'.
+module Scion.Server.Commands2 
+  ( handleRequest, KeepGoing )
+where
 
 import Scion.Server.Message
 
@@ -218,6 +223,9 @@ allCommands =
   , cmdListSupportedFlags
   , cmdListExposedModules
   , cmdLoad
+  , cmdListCabalComponents
+  , cmdCurrentComponent
+  , cmdForceUnload
   ]
 
 instance Message ModuleName where
@@ -364,3 +372,8 @@ cmdLoad =
                optArg "output" False $
       loadComponent'
 
+cmdCurrentComponent :: Cmd
+cmdCurrentComponent = Cmd "current-component" $ noArgs $ getActiveComponent
+
+cmdForceUnload :: Cmd
+cmdForceUnload = Cmd "force-unload" $ noArgs $ unload

server/Scion/Server/Message.hs

@@ -212,6 +212,18 @@ instance Message a => Message [a] where
   toMsg ls = MsgList $ map toMsg ls
   fromMsg MsgNull = pure []
   fromMsg (MsgList l) = mapM fromMsg l
+
+-- TODO: Is this instance OK?  It does not allow nested Maybe types.
+-- It's meant to be more in line with the JSON/BSON data model.  I.e.,
+--
+--     Maybe X = nullable X
+--
+instance Message a => Message (Maybe a) where
+  toMsg Nothing = MsgNull
+  toMsg (Just x) = toMsg x
+  fromMsg MsgNull = pure Nothing -- Masks 'Just ()' and 'Just Nothing'
+                                 -- as 'Nothing'
+  fromMsg x = Just <$> fromMsg x
 
 ------------------------------------------------------------------------
 -- * Sending and Receiving Messages