Enforce utf8 in eval plugin

Author: berberman

Diff for: plugins/hls-eval-plugin/src/Ide/Plugin/Eval/Code.hs

@@ -21,10 +21,11 @@ import           Ide.Plugin.Eval.Types          (Language (Plain), Loc,
                                                  Section (sectionLanguage),
                                                  Test (..), Txt, locate,
                                                  locate0)
-import           InteractiveEval                (getContext, parseImportDecl,
-                                                 runDecls, setContext)
+import           InteractiveEval                (execOptions, getContext,
+                                                 parseImportDecl, runDecls,
+                                                 setContext)
 import           Language.LSP.Types.Lens        (line, start)
-import           System.IO.Extra                (newTempFile, readFile')
+import           System.IO.Extra                (newTempFile, readFileUTF8')
 
 -- | Return the ranges of the expression and result parts of the given test
 testRanges :: Test -> (Range, Range)
@@ -95,8 +96,13 @@ evalExtensions =
 evalSetup :: Ghc ()
 evalSetup = do
     preludeAsP <- parseImportDecl "import qualified Prelude as P"
+    encodingAsP <- parseImportDecl "import GHC.IO.Encoding as P"
     context <- getContext
-    setContext (IIDecl preludeAsP : context)
+    setContext (IIDecl encodingAsP : IIDecl preludeAsP : context)
+    execStmt "P.setLocaleEncoding P.utf8" execOptions >>= \case
+        ExecComplete (Left err) _ -> error $ "failed to set encoding in eval setup: " <> show err
+        ExecComplete (Right _) _ -> pure ()
+        ExecBreak{} -> error "breakpoints are not supported"
 
 -- | A wrapper of 'InteractiveEval.execStmt', capturing the execution result
 myExecStmt :: String -> ExecOptions -> Ghc (Either String (Maybe String))
@@ -106,7 +112,7 @@ myExecStmt stmt opts = do
     modifySession $ \hsc -> hsc {hsc_IC = setInteractivePrintName (hsc_IC hsc) evalPrint}
     result <- execStmt stmt opts >>= \case
               ExecComplete (Left err) _ -> pure $ Left $ show err
-              ExecComplete (Right _) _ -> liftIO $ Right . (\x -> if null x then Nothing else Just x) <$> readFile' temp
+              ExecComplete (Right _) _ -> liftIO $ Right . (\x -> if null x then Nothing else Just x) <$> readFileUTF8' temp
               ExecBreak{} -> pure $ Right $ Just "breakpoints are not supported"
     liftIO purge
     pure result