Remove state cwd

app/MainHie.hs

@@ -5,6 +5,7 @@
 module Main where
 
 import           Control.Monad
+import           Control.Monad.Trans.Maybe
 import           Control.Concurrent
 import           Control.Exception
 import           Control.Logging
@@ -24,6 +25,8 @@ import           Haskell.Ide.Engine.Transport.JsonStdio
 import           Haskell.Ide.Engine.Types
 import           Options.Applicative.Simple
 import qualified Paths_haskell_ide_engine as Meta
+import           System.Directory
+import           System.Environment
 
 -- ---------------------------------------------------------------------
 -- plugins
@@ -92,6 +95,14 @@ run opts = do
       then setLogLevel LevelDebug
       else setLogLevel LevelError
 
+    -- We change the current working dirextory of HIE to user home
+    -- directory so that plugins do not depend on cwd. All paths to
+    -- all project files referenced in commands are expected to be
+    -- absolute. Cwd is state and we do not want state in what is
+    -- async system.
+
+    getUserHomeDirectory >>= mapM_ setCurrentDirectory
+
     logm $  "run entered for HIE " ++ version
     cin <- newChan :: IO (Chan ChannelRequest)
 
@@ -114,6 +125,13 @@ run opts = do
     -- At least one needs to be launched, othewise a threadDelay with a large
     -- number should be given. Or some other waiting action.
 
+getUserHomeDirectory :: IO (Maybe String)
+getUserHomeDirectory = do
+    -- On POSIX-like $HOME points to user home directory.
+    -- On Windows %USERPROFILE% points to user home directory.
+    runMaybeT (msum [ MaybeT $ lookupEnv "HOME"
+                    , MaybeT $ lookupEnv "USERPROFILE"])
+
 -- ---------------------------------------------------------------------
 
 -- |Do whatever it takes to get a request from the IDE.

haskell-ide-engine.cabal

@@ -66,6 +66,7 @@ executable hie
                      , Cabal >= 1.22
                      , aeson
                      , containers
+                     , directory
                      , ghc
                      , ghc-mod
                      , gitrev >= 1.1

src/Haskell/Ide/Engine/BasePlugin.hs

@@ -4,7 +4,6 @@
 module Haskell.Ide.Engine.BasePlugin where
 
 import           Control.Monad
-import           Control.Monad.IO.Class
 import           Data.Aeson
 import           Data.Foldable
 import           Data.List
@@ -20,7 +19,6 @@ import           Haskell.Ide.Engine.PluginUtils
 import           Options.Applicative.Simple (simpleVersion)
 import qualified Paths_haskell_ide_engine as Meta
 import           Prelude hiding (log)
-import           System.Directory
 
 -- ---------------------------------------------------------------------
 
@@ -70,26 +68,6 @@ baseDescriptor = PluginDescriptor
                         }
           , cmdFunc = commandDetailCmd
           }
-      , Command
-          { cmdDesc = CommandDesc
-                        { cmdName = "pwd"
-                        , cmdUiDescription = "return the current working directory for the HIE process"
-                        , cmdFileExtensions = []
-                        , cmdContexts = [CtxNone]
-                        , cmdAdditionalParams = []
-                        }
-          , cmdFunc = pwdCmd
-          }
-      , Command
-          { cmdDesc = CommandDesc
-                        { cmdName = "cwd"
-                        , cmdUiDescription = "change the current working directory for the HIE process"
-                        , cmdFileExtensions = []
-                        , cmdContexts = [CtxNone]
-                        , cmdAdditionalParams = [RP "dir" "the new working directory" PtFile]
-                       }
-          , cmdFunc = cwdCmd
-          }
       ]
   , pdExposedServices = []
   , pdUsedServices    = []
@@ -136,21 +114,6 @@ commandDetailCmd _ req = do
     Right _ -> return (IdeResponseError (IdeError
                 InternalError "commandDetailCmd: ghc’s exhaustiveness checker is broken" Nothing))
 
-
-pwdCmd :: CommandFunc
-pwdCmd _ _ = do
-  dir <- liftIO $ getCurrentDirectory
-  return (IdeResponseOk (String $ T.pack dir))
-
-cwdCmd :: CommandFunc
-cwdCmd _ req = do
-  case Map.lookup "dir" (ideParams req) of
-    Nothing -> return $ missingParameter "dir"
-    Just (ParamFileP dir) -> do
-      liftIO $ setCurrentDirectory (T.unpack dir)
-      return (IdeResponseOk Null)
-    Just x -> return $ incorrectParameter "dir" ("ParamFile"::String) x
-
 -- ---------------------------------------------------------------------
 
 version :: String