Use haskeline-0.8 (#540)

The `MonadException` class was removed in favor of `MonadCatch`, so we
can remove its instances, enabling us to remove the library dependency
on haskeline.

To simplify dependency resolution with GHC < 8.10, this also disables
the executable in that configuration.

hnix.cabal

@@ -910,7 +910,6 @@ library
         Nix.Options.Parser
     build-depends:
         base16-bytestring >= 0.1.1 && < 0.2
-      , haskeline >= 0.7.4.2 && < 0.8
       , pretty-show >= 1.9.5 && < 1.11
       , serialise >= 0.2.1 && < 0.3
   -- if !flag(profiling)
@@ -938,7 +937,7 @@ executable hnix
     , exceptions
     , filepath
     , free
-    , haskeline
+    , haskeline >= 0.8.0.0 && < 0.9
     , hnix
     , mtl
     , optparse-applicative
@@ -954,6 +953,10 @@ executable hnix
     , unordered-containers
   if flag(optimize)
     ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively -O2
+  if impl(ghc < 8.10)
+    -- GHC < 8.10 comes with haskeline < 0.8, which we don't support.
+    -- To simplify CI, we just disable the component.
+    buildable: False
   if impl(ghcjs)
     buildable: False
   default-language: Haskell2010

main/Repl.hs

@@ -52,19 +52,14 @@ import           Control.Monad.Identity
 import           Control.Monad.Reader
 import           Control.Monad.State.Strict
 
-import           System.Console.Haskeline.MonadException
-import           System.Console.Repline        hiding ( options )
+import           System.Console.Repline        hiding ( options, prefix )
 import           System.Environment
 import           System.Exit
 
 
-main :: (MonadNix e t f m, MonadIO m, MonadException m) => m ()
+main :: (MonadNix e t f m, MonadIO m, MonadMask m) => m ()
 main = flip evalStateT initState
-#if MIN_VERSION_repline(0, 2, 0)
     $ evalRepl (return prefix) cmd options (Just ':') completer welcomeText
-#else
-    $ evalRepl prefix cmd options completer welcomeText
-#endif
  where
   prefix = "hnix> "
   welcomeText =
@@ -86,7 +81,7 @@ initState :: MonadIO m => IState t f m
 initState = IState M.empty
 
 type Repl e t f m = HaskelineT (StateT (IState t f m) m)
-hoistErr :: MonadIO m => Result a -> Repl e t f m a
+hoistErr :: (MonadIO m, MonadThrow m) => Result a -> Repl e t f m a
 hoistErr (Success val) = return val
 hoistErr (Failure err) = do
   liftIO $ print err
@@ -98,7 +93,7 @@ hoistErr (Failure err) = do
 
 exec
   :: forall e t f m
-   . (MonadNix e t f m, MonadIO m, MonadException m)
+   . (MonadNix e t f m, MonadIO m)
   => Bool
   -> Text.Text
   -> Repl e t f m (NValue t f m)
@@ -129,7 +124,7 @@ exec update source = do
 
 
 cmd
-  :: (MonadNix e t f m, MonadIO m, MonadException m)
+  :: (MonadNix e t f m, MonadIO m)
   => String
   -> Repl e t f m ()
 cmd source = do
@@ -153,7 +148,7 @@ browse _ = do
 
 -- :load command
 load
-  :: (MonadNix e t f m, MonadIO m, MonadException m)
+  :: (MonadNix e t f m, MonadIO m)
   => [String]
   -> Repl e t f m ()
 load args = do
@@ -162,7 +157,7 @@ load args = do
 
 -- :type command
 typeof
-  :: (MonadNix e t f m, MonadException m, MonadIO m)
+  :: (MonadNix e t f m, MonadIO m)
   => [String]
   -> Repl e t f m ()
 typeof args = do
@@ -199,7 +194,7 @@ comp n = do
                                       )
 
 options
-  :: (MonadNix e t f m, MonadIO m, MonadException m)
+  :: (MonadNix e t f m, MonadIO m)
   => [(String, [String] -> Repl e t f m ())]
 options =
   [ ( "load"
@@ -213,7 +208,7 @@ options =
 
 help
   :: forall e t f m
-   . (MonadNix e t f m, MonadIO m, MonadException m)
+   . (MonadNix e t f m, MonadIO m)
   => [String]
   -> Repl e t f m ()
 help _ = liftIO $ do

src/Nix/Fresh.hs

@@ -21,9 +21,6 @@ import           Control.Monad.Reader
 import           Control.Monad.Ref
 import           Control.Monad.ST
 import           Data.Typeable
-#ifdef MIN_VERSION_haskeline
-import System.Console.Haskeline.MonadException hiding(catch)
-#endif
 
 import           Nix.Var
 import           Nix.Thunk
@@ -42,9 +39,7 @@ newtype FreshIdT i m a = FreshIdT { unFreshIdT :: ReaderT (Var m i) m a }
     , MonadIO
     , MonadCatch
     , MonadThrow
-#ifdef MIN_VERSION_haskeline
-    , MonadException
-#endif
+    , MonadMask
     )
 
 instance MonadTrans (FreshIdT i) where

src/Nix/Standard.hs

@@ -47,9 +47,6 @@ import           Nix.Utils.Fix1
 import           Nix.Value
 import           Nix.Value.Monad
 import           Nix.Var
-#ifdef MIN_VERSION_haskeline
-import           System.Console.Haskeline.MonadException hiding(catch)
-#endif
 
 -- All of the following type classes defer to the underlying 'm'.
 
@@ -69,21 +66,6 @@ deriving instance MonadInstantiate (t (Fix1T t m) m) => MonadInstantiate (Fix1T
 deriving instance MonadExec (t (Fix1T t m) m) => MonadExec (Fix1T t m)
 deriving instance MonadIntrospect (t (Fix1T t m) m) => MonadIntrospect (Fix1T t m)
 
-#ifdef MIN_VERSION_haskeline
--- For whatever reason, using the default StateT instance provided by
--- haskeline does not work.
-instance MonadException m
-  => MonadException(StateT(HashMap FilePath NExprLoc) m) where
-  controlIO f = StateT $ \s -> controlIO $ \(RunIO run) -> let
-    run' = RunIO(fmap(StateT . const) . run . flip runStateT s)
-    in fmap(flip runStateT s) $ f run'
-
-instance MonadException m => MonadException(Fix1T StandardTF m) where
-  controlIO f = mkStandardT $ controlIO $ \(RunIO run) ->
-    let run' = RunIO(fmap mkStandardT . run . runStandardT)
-    in runStandardT <$> f run'
-#endif
-
 type MonadFix1T t m = (MonadTrans (Fix1T t), Monad (t (Fix1T t m) m))
 
 instance (MonadFix1T t m, MonadRef m) => MonadRef (Fix1T t m) where
@@ -219,6 +201,7 @@ newtype StandardTF r m a
     , MonadIO
     , MonadCatch
     , MonadThrow
+    , MonadMask
     , MonadReader (Context r (StdValue r))
     , MonadState (HashMap FilePath NExprLoc)
     )

src/Nix/Utils/Fix1.hs

@@ -48,6 +48,7 @@ deriving instance MonadFix (t (Fix1T t m) m) => MonadFix (Fix1T t m)
 deriving instance MonadIO (t (Fix1T t m) m) => MonadIO (Fix1T t m)
 deriving instance MonadCatch (t (Fix1T t m) m) => MonadCatch (Fix1T t m)
 deriving instance MonadThrow (t (Fix1T t m) m) => MonadThrow (Fix1T t m)
+deriving instance MonadMask (t (Fix1T t m) m) => MonadMask (Fix1T t m)
 
 deriving instance MonadReader e (t (Fix1T t m) m) => MonadReader e (Fix1T t m)
 deriving instance MonadState s (t (Fix1T t m) m) => MonadState s (Fix1T t m)