ihaskell: add `use-hlint` flag

ihaskell.cabal

@@ -49,6 +49,11 @@ data-files:
     jupyterlab-ihaskell/labextension/static/*.js
     jupyterlab-ihaskell/labextension/static/*.json
 
+flag use-hlint
+  description: Include HLint support
+  default:     True
+  manual:      True
+
 library
   hs-source-dirs:      src
   default-language:    Haskell2010
@@ -72,7 +77,6 @@ library
                        ghc-parser           >=0.2.1,
                        ghc-paths            >=0.1,
                        haskeline            -any,
-                       hlint                >=1.9,
                        http-client          >= 0.4,
                        http-client-tls      >= 0.2,
                        mtl                  >=2.1,
@@ -93,10 +97,6 @@ library
                        ipython-kernel       >=0.10.2.0,
                        ghc-boot             >=8.0 && <9.1
 
-  if impl (ghc < 8.10)
-    build-depends:
-                       haskell-src-exts     >=1.18
-
   exposed-modules: IHaskell.Display
                    IHaskell.Convert
                    IHaskell.Convert.Args
@@ -106,7 +106,6 @@ library
                    IHaskell.Eval.Inspect
                    IHaskell.Eval.Evaluate
                    IHaskell.Eval.Info
-                   IHaskell.Eval.Lint
                    IHaskell.Eval.Parser
                    IHaskell.Eval.Hoogle
                    IHaskell.Eval.ParseShell
@@ -124,6 +123,14 @@ library
   other-modules:
                    StringUtils
 
+  if flag(use-hlint)
+    exposed-modules: IHaskell.Eval.Lint
+    build-depends: hlint >=1.9
+    cpp-options: -DUSE_HLINT
+
+  if flag(use-hlint) && impl (ghc < 8.10)
+    build-depends: haskell-src-exts     >=1.18
+
 executable ihaskell
   -- .hs or .lhs file containing the Main module.
   main-is:             Main.hs

src/IHaskell/Eval/Evaluate.hs

@@ -68,13 +68,16 @@ import           GHC hiding (Stmt, TypeSig)
 import           IHaskell.Types
 import           IHaskell.IPython
 import           IHaskell.Eval.Parser
-import           IHaskell.Eval.Lint
 import           IHaskell.Display
 import qualified IHaskell.Eval.Hoogle as Hoogle
 import           IHaskell.Eval.Util
 import           IHaskell.BrokenPackages
 import           StringUtils (replace, split, strip, rstrip)
 
+#ifdef USE_HLINT
+import           IHaskell.Eval.Lint
+#endif
+
 #if MIN_VERSION_ghc(9,0,0)
 import           GHC.Data.FastString
 #elif MIN_VERSION_ghc(8,2,0)
@@ -351,10 +354,13 @@ evaluate kernelState code output widgetHandler = do
   updated <- case errs of
                -- Only run things if there are no parse errors.
                [] -> do
+
+#ifdef USE_HLINT
                  when (getLintStatus kernelState /= LintOff) $ liftIO $ do
                    lintSuggestions <- lint code cmds
                    unless (noResults lintSuggestions) $
                      output (FinalResult lintSuggestions [] []) Success
+#endif
 
                  runUntilFailure kernelState (map unloc cmds ++ [storeItCommand execCount])
                -- Print all parse errors.