ihaskell: Remove partial-fields

GHC 8.4 and later have the `-Wpartial-fields` warning flag, so add it and
fix the warnings.

ihaskell.cabal

@@ -50,6 +50,10 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   ghc-options:         -Wall
+
+  if impl (ghc >= 8.4)
+    ghc-options:       -Wpartial-fields
+
   build-depends:
                        aeson                >=1.0,
                        base                 >=4.9,
@@ -123,6 +127,9 @@ executable ihaskell
                    Paths_ihaskell
   ghc-options: -threaded -rtsopts -Wall
 
+  if impl (ghc >= 8.4)
+    ghc-options:       -Wpartial-fields
+
   -- Other library packages from which modules are imported.
   default-language:    Haskell2010
   build-depends:
@@ -143,6 +150,10 @@ executable ihaskell
 Test-Suite hspec
     Type: exitcode-stdio-1.0
     Ghc-Options: -threaded -Wall
+
+    if impl (ghc >= 8.4)
+      ghc-options:     -Wpartial-fields
+
     Main-Is: Hspec.hs
     hs-source-dirs: src/tests
     other-modules:

src/IHaskell/Publish.hs

@@ -1,5 +1,7 @@
 {-# language NoImplicitPrelude, DoAndIfThenElse, OverloadedStrings, ExtendedDefaultRules #-}
-module IHaskell.Publish (publishResult) where
+module IHaskell.Publish
+  ( publishResult
+  ) where
 
 import           IHaskellPrelude
 
@@ -30,7 +32,7 @@ publishResult send replyHeader displayed updateNeeded poutput upager result = do
         case result of
           IntermediateResult{} -> False
           FinalResult{}        -> True
-      outs = outputs result
+      outs = evaluationOutputs result
 
   -- If necessary, clear all previous output and redraw.
   clear <- readMVar updateNeeded
@@ -49,11 +51,13 @@ publishResult send replyHeader displayed updateNeeded poutput upager result = do
     modifyMVar_ displayed (return . (outs :))
 
     -- If this has some pager output, store it for later.
-    let pager = pagerOut result
-    unless (null pager) $
-      if upager
-        then modifyMVar_ poutput (return . (++ pager))
-        else sendOutput $ Display pager
+    case result of
+      IntermediateResult _ -> pure ()
+      FinalResult _ pager _ ->
+        unless (null pager) $
+          if upager
+            then modifyMVar_ poutput (return . (++ pager))
+            else sendOutput $ Display pager
 
   where
     clearOutput = do

src/IHaskell/Types.hs

@@ -19,6 +19,7 @@ module IHaskell.Types (
     MimeType(..),
     DisplayData(..),
     EvaluationResult(..),
+    evaluationOutputs,
     ExecuteReplyStatus(..),
     KernelState(..),
     LintStatus(..),
@@ -248,21 +249,23 @@ instance ToJSON WidgetMethod where
   toJSON (CustomContent v) = object ["method" .= ("custom" :: Text), "content" .= v]
 
 -- | Output of evaluation.
-data EvaluationResult =
-                      -- | An intermediate result which communicates what has been printed thus
-                      -- far.
-                        IntermediateResult
-                          { outputs :: Display -- ^ Display outputs.
-                          }
-                      |
-                        FinalResult
-                          { outputs :: Display       -- ^ Display outputs.
-                          , pagerOut :: [DisplayData] -- ^ Mimebundles to display in the IPython
-                                                      -- pager.
-                          , commMsgs :: [WidgetMsg]  -- ^ Comm operations
-                          }
+data EvaluationResult
+  -- | An intermediate result which communicates what has been printed thus far.
+  = IntermediateResult
+        !Display -- ^ Display outputs.
+  | FinalResult
+        !Display       -- ^ Display outputs.
+        ![DisplayData] -- ^ Mimebundles to display in the IPython pager.
+        ![WidgetMsg]  -- ^ Comm operations
   deriving Show
 
+
+evaluationOutputs :: EvaluationResult -> Display
+evaluationOutputs er =
+  case er of
+    IntermediateResult outputs -> outputs
+    FinalResult outputs _ _ -> outputs
+
 -- | Duplicate a message header, giving it a new UUID and message type.
 dupHeader :: MessageHeader -> MessageType -> IO MessageHeader
 dupHeader hdr messageType = do

stack-8.4.yaml

@@ -26,7 +26,7 @@ extra-deps:
 ghc-options:
   # Eventually we want "$locals": -Wall -Wpartial-fields -Werror
   ghc-parser: -Wall -Wpartial-fields -Werror
-  ihaskell: -Wall -Werror
+  ihaskell: -Wall -Wpartial-fields -Werror
   ihaskell-widgets: -Wall -Wpartial-fields -Werror
 
 nix: