Fix incomplete pattern matches

Add `-Wincomplete-patterns` to the `ghc-options` field of the cabal file
and fix all warnings.

ihaskell.cabal

@@ -49,6 +49,7 @@ data-files:
 library
   hs-source-dirs:      src
   default-language:    Haskell2010
+  ghc-options:         -Wincomplete-patterns
   build-depends:
                        aeson                >=1.0,
                        base                 >=4.9,
@@ -124,6 +125,7 @@ executable ihaskell
 
   -- Other library packages from which modules are imported.
   default-language:    Haskell2010
+  ghc-options:         -Wincomplete-patterns
   build-depends:
                        ihaskell -any,
                        base                 >=4.9 && < 4.13,
@@ -150,6 +152,7 @@ Test-Suite hspec
         IHaskell.Test.Util
         IHaskell.Test.Parser
     default-language: Haskell2010
+    ghc-options:         -Wincomplete-patterns
     build-depends:
         base,
         ihaskell,

main/Main.hs

@@ -469,6 +469,9 @@ handleComm send kernelState req replyHeader = do
           pgrOut <- liftIO $ readMVar pagerOutput
           liftIO $ publish $ FinalResult disp (if toUsePager then pgrOut else []) []
           return kernelState { openComms = Map.delete uuid widgets }
+        x ->
+          -- Only sensible thing to do.
+          return kernelState
 
   -- Notify the frontend that the kernel is idle once again
   idleHeader <- liftIO $ dupHeader replyHeader StatusMessage

src/IHaskell/Eval/Evaluate.hs

@@ -234,6 +234,7 @@ initializeImports = do
 
   -- Generate import statements all Display modules.
   let capitalize :: String -> String
+      capitalize [] = []
       capitalize (first:rest) = Char.toUpper first : rest
 
       importFmt = "import IHaskell.Display.%s"
@@ -655,8 +656,9 @@ evalCommand _ (Directive LoadFile names) state = wrapExecution state $ do
                 doLoadModule filename modName
   return (ManyDisplay displays)
 
-evalCommand publish (Directive ShellCmd ('!':cmd)) state = wrapExecution state $
-  case words cmd of
+evalCommand publish (Directive ShellCmd cmd) state = wrapExecution state $
+  -- Assume the first character of 'cmd' is '!'.
+  case words $ drop 1 cmd of
     "cd":dirs -> do
       -- Get home so we can replace '~` with it.
       homeEither <- liftIO (try $ getEnv "HOME" :: IO (Either SomeException String))

src/IHaskell/Eval/Hoogle.hs

@@ -110,9 +110,8 @@ search string = do
 document :: String -> IO [HoogleResult]
 document string = do
   matchingResults <- filter matches <$> search string
-  let results = map toDocResult matchingResults
   return $
-    case results of
+    case mapMaybe toDocResult matchingResults of
       []  -> [NoResult "no matching identifiers found."]
       res -> res
 
@@ -123,7 +122,9 @@ document string = do
         _      -> False
     matches _ = False
 
-    toDocResult (SearchResult resp) = DocResult resp
+    toDocResult (SearchResult resp) = Just $ DocResult resp
+    toDocResult (DocResult _) = Nothing
+    toDocResult (NoResult _) = Nothing
 
 -- | Render a Hoogle search result into an output format.
 render :: OutputFormat -> HoogleResult -> String
@@ -233,7 +234,10 @@ renderDocs doc =
       bothAreCode s1 s2 =
                            isPrefixOf ">" (strip s1) &&
                            isPrefixOf ">" (strip s2)
-      isCode (s:_) = isPrefixOf ">" $ strip s
+      isCode xs =
+        case xs of
+          [] -> False
+          (s:_) -> isPrefixOf ">" $ strip s
       makeBlock lines =
                          if isCode lines
                            then div' "hoogle-code" $ unlines $ nonull lines

src/IHaskell/Eval/Lint.hs

@@ -115,6 +115,9 @@ createModule mode (Located line block) =
         Import impt      -> impt
         Module mod       -> mod
 
+        -- TODO: Properly handle the other constructors
+        _ -> []
+
     unparse :: ParseResult a -> Maybe a
     unparse (ParseOk a) = Just a
     unparse _ = Nothing

src/IHaskell/Eval/Parser.hs

@@ -239,11 +239,11 @@ joinFunctions blocks =
 parsePragma :: String       -- ^ Pragma string.
             -> Int          -- ^ Line number at which the directive appears.
             -> CodeBlock    -- ^ Pragma code block or a parse error.
-parsePragma ('{':'-':'#':pragma) line =
+parsePragma pragma line =
   let commaToSpace :: Char -> Char
       commaToSpace ',' = ' '
       commaToSpace x = x
-      pragmas = words $ takeWhile (/= '#') $ map commaToSpace pragma
+      pragmas = words $ takeWhile (/= '#') $ map commaToSpace $ drop 3 pragma
   in case pragmas of
     --empty string pragmas are unsupported
     [] -> Pragma (PragmaUnsupported "") []

src/IHaskell/Eval/Util.hs

@@ -246,6 +246,7 @@ doc sdoc = do
     string_txt (Pretty.Str s1) s2 = s1 ++ s2
     string_txt (Pretty.PStr s1) s2 = unpackFS s1 ++ s2
     string_txt (Pretty.LStr s1 _) s2 = unpackLitString s1 ++ s2
+    string_txt (Pretty.ZStr s1) s2 = CBS.unpack (fastZStringToByteString s1) ++ s2
 #endif
 
 -- | Initialize the GHC API. Run this as the first thing in the `runGhc`. This initializes some dyn

src/IHaskell/Flags.hs

@@ -94,6 +94,7 @@ help mode = showText (Wrap 100) $ helpText [] HelpFormatAll $ chooseMode mode
     chooseMode InstallKernelSpec = installKernelSpec
     chooseMode (Kernel _) = kernel
     chooseMode ConvertLhs = convert
+    chooseMode (ShowDefault _) = error "IHaskell.Flags.help: Should never happen."
 
 ghcLibFlag :: Flag Args
 ghcLibFlag = flagReq ["ghclib", "l"] (store GhcLibDir) "<path>" "Library directory for GHC."

src/tests/IHaskell/Test/Eval.hs

@@ -27,7 +27,7 @@ eval string = do
   let publish evalResult =
         case evalResult of
           IntermediateResult{} -> return ()
-          FinalResult outs page [] -> do
+          FinalResult outs page _ -> do
             modifyIORef outputAccum (outs :)
             modifyIORef pagerAccum (page :)
       noWidgetHandling s _ = return s