prepareAutogen skips its work if a cabal file does not exist.

src/GHCModi.hs

@@ -28,6 +28,7 @@ import Data.List (intercalate)
 import Data.List.Split (splitOn)
 import Data.Version (showVersion)
 import Language.Haskell.GhcMod
+import Language.Haskell.GhcMod.Internal (cradle)
 import Paths_ghc_mod
 import System.Console.GetOpt
 import System.Directory (setCurrentDirectory)
@@ -87,7 +88,7 @@ run opt ref = flip E.catches handlers $ do
     let rootdir = cradleRootDir cradle0
 --        c = cradle0 { cradleCurrentDir = rootdir } TODO: ?????
     setCurrentDirectory rootdir
-    prepareAutogen
+    prepareAutogen cradle0
     -- Asynchronous db loading starts here.
     symdbreq <- newSymDbReq opt
     (res, _) <- runGhcModT opt $ getCurrentWorld >>= loop symdbreq ref
@@ -129,7 +130,7 @@ loop symdbreq ref world = do
     when changed $ do
         liftIO $ ungetCommand ref cmdArg
         E.throw Restart
-    liftIO $ prepareAutogen
+    cradle >>= liftIO . prepareAutogen
     let (cmd,arg') = break (== ' ') cmdArg
         arg = dropWhile (== ' ') arg'
     (ret,ok) <- case cmd of

src/Misc.hs

@@ -21,15 +21,16 @@ import Control.Applicative ((<$>))
 import Control.Concurrent (threadDelay)
 import Control.Concurrent.Async (Async, async, wait)
 import Control.Exception (Exception)
-import Control.Monad (unless)
+import Control.Monad (unless, when)
 import CoreMonad (liftIO)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
 import Data.List (isPrefixOf)
+import Data.Maybe (isJust)
 import Data.Time (UTCTime)
 import Data.Typeable (Typeable)
 import System.Directory (getModificationTime, doesDirectoryExist, getDirectoryContents)
-import System.Process
 import System.IO (openBinaryFile, IOMode(..))
+import System.Process
 
 import Language.Haskell.GhcMod
 import Language.Haskell.GhcMod.Internal
@@ -168,8 +169,8 @@ watch n hdl = do
         threadDelay 100000
         watch (n - 1) hdl
 
-prepareAutogen :: IO ()
-prepareAutogen = do
+prepareAutogen :: Cradle -> IO ()
+prepareAutogen crdl = when (isJust $ cradleCabalFile crdl) $ do
     prepared <- isAutogenPrepared
     unless prepared $ do
         hdl <- build