Remove all uses of fromJust

src/IHaskell/Convert/Args.hs

@@ -35,11 +35,11 @@ fromJustConvertSpec convertSpec = convertSpec
   , convertLhsStyle = Identity $ fromMaybe (LT.pack <$> lhsStyleBird) (convertLhsStyle convertSpec)
   }
   where
-    toIpynb = fromMaybe (error "Error: direction for conversion unknown")
+    toIpynb = fromMaybe (error "fromJustConvertSpec: direction for conversion unknown")
                 (convertToIpynb convertSpec)
     (inputFile, outputFile) =
       case (convertInput convertSpec, convertOutput convertSpec) of
-        (Nothing, Nothing) -> error "Error: no files specified for conversion"
+        (Nothing, Nothing) -> error "fromJustConvertSpec: no files specified for conversion"
         (Just i, Nothing)
           | toIpynb -> (i, dropExtension i <.> "ipynb")
           | otherwise -> (i, dropExtension i <.> "lhs")

src/IHaskell/Eval/Evaluate.hs

@@ -36,7 +36,7 @@ import           System.IO (hGetChar, hSetEncoding, utf8)
 import           System.Random (getStdGen, randomRs)
 import           System.Process
 import           System.Exit
-import           Data.Maybe (fromJust)
+import           Data.Maybe (mapMaybe)
 import           System.Environment (getEnv)
 
 import qualified GHC.Paths
@@ -532,7 +532,7 @@ evalCommand _output (Directive SetDynFlag flagsStr) state = safely state $ do
           }
     else do
       -- Apply all IHaskell flag updaters to the state to get the new state
-      let state' = foldl' (.) id (map (fromJust . ihaskellFlagUpdater) ihaskellFlags) state
+      let state' = foldl' (.) id (mapMaybe ihaskellFlagUpdater ihaskellFlags) state
       errs <- setFlags ghcFlags
       let disp =
             case errs of
@@ -689,21 +689,18 @@ evalCommand publish (Directive ShellCmd cmd) state = wrapExecution state $
             modifyMVar_ outputAccum (return . (++ nextChunk))
 
             -- Check if we're done.
-            exitCode <- getProcessExitCode process
-            let computationDone = isJust exitCode
-
-            when computationDone $ do
-              next <- readChars pipe "" maxSize
-              modifyMVar_ outputAccum (return . (++ next))
-
-            if not computationDone
-              then do
+            mExitCode <- getProcessExitCode process
+            case mExitCode of
+              Nothing -> do
+                -- Process still running
+                next <- readChars pipe "" maxSize
+                modifyMVar_ outputAccum (return . (++ next))
                 -- Write to frontend and repeat.
                 readMVar outputAccum >>= output
                 loop
-              else do
+              Just exitCode -> do
                 out <- readMVar outputAccum
-                case fromJust exitCode of
+                case exitCode of
                   ExitSuccess -> return $ Display [plain out]
                   ExitFailure code -> do
                     let errMsg = "Process exited with error code " ++ show code

src/IHaskell/Eval/Hoogle.hs

@@ -248,11 +248,8 @@ extractPackageName lnk = do
   return $ pieces List.!! (latestLoc - 1)
 
 extractModuleName :: String -> Maybe String
-extractModuleName lnk = do
-  let pieces = split "/" lnk
-  guard $ not $ null pieces
-  let html = fromJust $ lastMay pieces
-  return $ replace "-" "." $ takeWhile (/= '.') html
+extractModuleName lnk =
+  replace "-" "." . takeWhile (/= '.') <$> lastMay (split "/" lnk)
 
 div' :: String -> String -> String
 div' = printf "<div class='%s'>%s</div>"

src/IHaskell/IPython.hs

@@ -196,9 +196,8 @@ subHome path = SH.shelly $ do
 parseVersion :: String -> Maybe [Int]
 parseVersion versionStr =
   let versions = map readMay $ split "." versionStr
-      parsed = all isJust versions
-  in if parsed
-       then Just $ map fromJust versions
+  in if all isJust versions
+       then Just $ catMaybes versions
        else Nothing
 
 -- | Get the absolute path to this IHaskell executable.

src/IHaskell/IPython/Stdin.hs

@@ -31,6 +31,7 @@ import           Control.Concurrent
 import           Control.Applicative ((<$>))
 import           GHC.IO.Handle
 import           GHC.IO.Handle.Types
+import           System.FilePath ((</>))
 import           System.Posix.IO
 import           System.IO.Unsafe
 
@@ -47,7 +48,9 @@ stdinInterface = unsafePerformIO newEmptyMVar
 fixStdin :: String -> IO ()
 fixStdin dir = do
   -- Initialize the stdin interface.
-  profile <- fromJust . readMay <$> readFile (dir ++ "/.kernel-profile")
+  let fpath = dir </> ".kernel-profile"
+  profile <- fromMaybe (error $ "fixStdin: Failed reading " ++ fpath)
+              . readMay <$> readFile fpath
   interface <- serveStdin profile
   putMVar stdinInterface interface
   void $ forkIO $ stdinOnce dir
@@ -86,7 +89,9 @@ getInputLine dir = do
 
   -- Send a request for input.
   uuid <- UUID.random
-  parentHdr <- fromJust . readMay <$> readFile (dir ++ "/.last-req-header")
+  let fpath = dir </> ".last-req-header"
+  parentHdr <- fromMaybe (error $ "getInputLine: Failed reading " ++ fpath)
+                . readMay <$> readFile fpath
   let hdr = MessageHeader (mhIdentifiers parentHdr) (Just parentHdr) mempty
               uuid (mhSessionId parentHdr) (mhUsername parentHdr) InputRequestMessage
   let msg = RequestInput hdr ""