Add a few more session-inspection functions.

src/Scion/Session.hs

@@ -29,7 +29,7 @@ import Scion.Cabal ( CabalException )
 import           Control.Applicative
 import           Control.Concurrent
 import           Control.Exception ( throwIO )
-import           Control.Monad ( when, unless, forever )
+import           Control.Monad ( when, unless, forever, filterM )
 import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
 import           Data.Char ( ord )
@@ -39,14 +39,15 @@ import           Data.Time.Clock.POSIX ( posixSecondsToUTCTime )
 import           System.Directory ( doesFileExist, getTemporaryDirectory,
                                     removeDirectoryRecursive )
 import           System.Exit ( ExitCode(..) )
-import           System.FilePath ( dropFileName, (</>), takeFileName )
+import           System.FilePath ( dropFileName, (</>), takeFileName, makeRelative )
 import           System.IO
 import           System.IO.Temp ( createTempDirectory )
 import           System.PosixCompat.Files ( getFileStatus, modificationTime )
 import           System.Process ( getProcessExitCode, terminateProcess )
 
 -- -------------------------------------------------------------------
 
+-- | Throw a 'ScionException' if the file does not exist.
 ensureFileExists :: FilePath -> ScionM ()
 ensureFileExists file = do
   ok <- io $ doesFileExist  file
@@ -80,6 +81,7 @@ createSession sc0@FileConfig{ sc_fileName = file } = do
         , sessionOutputDir = outdir
         , sessionModuleGraph = graph
         , sessionLastCompilation = rslt
+        , sessionHomeDir = working_dir
         }
 
   registerSession sid sess0
@@ -115,6 +117,7 @@ createSession sc0@CabalConfig{ sc_cabalFile = file } = do
         , sessionOutputDir = build_dir
         , sessionModuleGraph = graph
         , sessionLastCompilation = rslt
+        , sessionHomeDir = working_dir
         }
 
   registerSession sid sess0
@@ -137,6 +140,7 @@ createSession sc@EmptyConfig{} = do
         , sessionOutputDir = outdir
         , sessionModuleGraph = graph
         , sessionLastCompilation = rslt
+        , sessionHomeDir = working_dir
         }
 
   registerSession sid sess0
@@ -162,6 +166,9 @@ sessionNotes :: SessionId -> ScionM Notes
 sessionNotes sid = do
   compilationNotes . sessionLastCompilation <$> getSessionState sid
 
+sessionModules :: SessionId -> ScionM [ModuleSummary]
+sessionModules sid = sessionModuleGraph <$> getSessionState sid
+
 supportedLanguagesAndExtensions :: ScionM [Extension]
 supportedLanguagesAndExtensions = do
   exts <- getExtensions
@@ -365,3 +372,13 @@ ignoreMostErrors act = do
      HandlerM $ \(ex :: RecConError) -> return (Left (show ex))
     ]
 
+fileSessions :: FilePath -> ScionM [SessionId]
+fileSessions path = do 
+  filterM (fileInSession path) =<< activeSessions
+
+fileInSession :: FilePath -> SessionId -> ScionM Bool
+fileInSession path0 sid = do
+  home <- sessionHomeDir <$> getSessionState sid
+  let path = makeRelative home path0
+  mods <- sessionModules sid
+  return $ not $ null [ m | m <- mods, ms_location m == path ]

src/Scion/Types/Monad.hs

@@ -102,6 +102,10 @@ doesSessionExist sid = ScionM $ \r -> do
     Just _  -> return True
     Nothing -> return False
 
+activeSessions :: ScionM [SessionId]
+activeSessions = ScionM $ \r -> do
+  M.keys . gsSessions <$> readIORef r
+
 -- | Unregister a 'SessionId'.  NOTE: Does not stop the worker.
 unregisterSession :: SessionId -> ScionM ()
 unregisterSession sid = ScionM $ \r ->

src/Scion/Types/Session.hs

@@ -124,6 +124,8 @@ data SessionState = SessionState
     -- caches to speed things up.
   , sessionModuleGraph :: [ModuleSummary]
   , sessionLastCompilation :: CompilationResult
+  , sessionHomeDir :: FilePath
+    -- ^ All file paths are relative to this directory.
   } deriving (Show)
 
 instance Binary SessionConfig where
@@ -217,7 +219,8 @@ data ModuleSummary = ModuleSummary
 
 instance Show ModuleSummary where
   show ms =
-    "<summary:" ++ show (ms_module ms) ++ ">"
+    "<summary:" ++ show (ms_module ms) ++ "," ++
+    ms_location ms ++ ">"
 
 instance Binary ModuleSummary where
   put (ModuleSummary mdl ft imps loc) =