Add setConfig as an analogue to getConfig (#414)

Author: pgujjula

lsp/src/Language/LSP/Server.hs

@@ -26,6 +26,7 @@ module Language.LSP.Server
 
   , getClientCapabilities
   , getConfig
+  , setConfig
   , getRootPath
   , getWorkspaceFolders
 

lsp/src/Language/LSP/Server/Core.hs

@@ -441,12 +441,18 @@ freshLspId = do
 -- ---------------------------------------------------------------------
 
 -- | The current configuration from the client as set via the @initialize@ and
--- @workspace/didChangeConfiguration@ requests.
+-- @workspace/didChangeConfiguration@ requests, as well as by calls to
+-- 'setConfig'.
 getConfig :: MonadLsp config m => m config
 getConfig = getsState resConfig
 
 {-# INLINE getConfig #-}
 
+setConfig :: MonadLsp config m => config -> m ()
+setConfig config = stateState resConfig (const ((), config))
+
+{-# INLINE setConfig #-}
+
 getClientCapabilities :: MonadLsp config m => m J.ClientCapabilities
 getClientCapabilities = resClientCapabilities <$> getLspEnv