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|
{-# LANGUAGE CPP, DeriveFunctor, RankNTypes #-}
{-# OPTIONS_GHC -funbox-strict-fields #-}
-- -----------------------------------------------------------------------------
--
-- (c) The University of Glasgow, 2010
--
-- The Session type and related functionality
--
-- -----------------------------------------------------------------------------
module GhcMonad (
-- * 'Ghc' monad stuff
GhcMonad(..),
Ghc(..),
GhcT(..), liftGhcT,
reflectGhc, reifyGhc,
getSessionDynFlags,
liftIO,
Session(..), withSession, modifySession, withTempSession,
-- ** Warnings
logWarnings, printException,
WarnErrLogger, defaultWarnErrLogger
) where
import GhcPrelude
import MonadUtils
import HscTypes
import DynFlags
import Exception
import ErrUtils
import Control.Monad
import Data.IORef
-- -----------------------------------------------------------------------------
-- | A monad that has all the features needed by GHC API calls.
--
-- In short, a GHC monad
--
-- - allows embedding of IO actions,
--
-- - can log warnings,
--
-- - allows handling of (extensible) exceptions, and
--
-- - maintains a current session.
--
-- If you do not use 'Ghc' or 'GhcT', make sure to call 'GHC.initGhcMonad'
-- before any call to the GHC API functions can occur.
--
class (Functor m, MonadIO m, ExceptionMonad m, HasDynFlags m) => GhcMonad m where
getSession :: m HscEnv
setSession :: HscEnv -> m ()
-- | Call the argument with the current session.
withSession :: GhcMonad m => (HscEnv -> m a) -> m a
withSession f = getSession >>= f
-- | Grabs the DynFlags from the Session
getSessionDynFlags :: GhcMonad m => m DynFlags
getSessionDynFlags = withSession (return . hsc_dflags)
-- | Set the current session to the result of applying the current session to
-- the argument.
modifySession :: GhcMonad m => (HscEnv -> HscEnv) -> m ()
modifySession f = do h <- getSession
setSession $! f h
withSavedSession :: GhcMonad m => m a -> m a
withSavedSession m = do
saved_session <- getSession
m `gfinally` setSession saved_session
-- | Call an action with a temporarily modified Session.
withTempSession :: GhcMonad m => (HscEnv -> HscEnv) -> m a -> m a
withTempSession f m =
withSavedSession $ modifySession f >> m
-- -----------------------------------------------------------------------------
-- | A monad that allows logging of warnings.
logWarnings :: GhcMonad m => WarningMessages -> m ()
logWarnings warns = do
dflags <- getSessionDynFlags
liftIO $ printOrThrowWarnings dflags warns
-- -----------------------------------------------------------------------------
-- | A minimal implementation of a 'GhcMonad'. If you need a custom monad,
-- e.g., to maintain additional state consider wrapping this monad or using
-- 'GhcT'.
newtype Ghc a = Ghc { unGhc :: Session -> IO a } deriving (Functor)
-- | The Session is a handle to the complete state of a compilation
-- session. A compilation session consists of a set of modules
-- constituting the current program or library, the context for
-- interactive evaluation, and various caches.
data Session = Session !(IORef HscEnv)
instance Applicative Ghc where
pure a = Ghc $ \_ -> return a
g <*> m = do f <- g; a <- m; return (f a)
instance Monad Ghc where
m >>= g = Ghc $ \s -> do a <- unGhc m s; unGhc (g a) s
instance MonadIO Ghc where
liftIO ioA = Ghc $ \_ -> ioA
instance MonadFix Ghc where
mfix f = Ghc $ \s -> mfix (\x -> unGhc (f x) s)
instance ExceptionMonad Ghc where
gcatch act handle =
Ghc $ \s -> unGhc act s `gcatch` \e -> unGhc (handle e) s
gmask f =
Ghc $ \s -> gmask $ \io_restore ->
let
g_restore (Ghc m) = Ghc $ \s -> io_restore (m s)
in
unGhc (f g_restore) s
instance HasDynFlags Ghc where
getDynFlags = getSessionDynFlags
instance GhcMonad Ghc where
getSession = Ghc $ \(Session r) -> readIORef r
setSession s' = Ghc $ \(Session r) -> writeIORef r s'
-- | Reflect a computation in the 'Ghc' monad into the 'IO' monad.
--
-- You can use this to call functions returning an action in the 'Ghc' monad
-- inside an 'IO' action. This is needed for some (too restrictive) callback
-- arguments of some library functions:
--
-- > libFunc :: String -> (Int -> IO a) -> IO a
-- > ghcFunc :: Int -> Ghc a
-- >
-- > ghcFuncUsingLibFunc :: String -> Ghc a -> Ghc a
-- > ghcFuncUsingLibFunc str =
-- > reifyGhc $ \s ->
-- > libFunc $ \i -> do
-- > reflectGhc (ghcFunc i) s
--
reflectGhc :: Ghc a -> Session -> IO a
reflectGhc m = unGhc m
-- > Dual to 'reflectGhc'. See its documentation.
reifyGhc :: (Session -> IO a) -> Ghc a
reifyGhc act = Ghc $ act
-- -----------------------------------------------------------------------------
-- | A monad transformer to add GHC specific features to another monad.
--
-- Note that the wrapped monad must support IO and handling of exceptions.
newtype GhcT m a = GhcT { unGhcT :: Session -> m a }
deriving (Functor)
liftGhcT :: m a -> GhcT m a
liftGhcT m = GhcT $ \_ -> m
instance Applicative m => Applicative (GhcT m) where
pure x = GhcT $ \_ -> pure x
g <*> m = GhcT $ \s -> unGhcT g s <*> unGhcT m s
instance Monad m => Monad (GhcT m) where
m >>= k = GhcT $ \s -> do a <- unGhcT m s; unGhcT (k a) s
instance MonadIO m => MonadIO (GhcT m) where
liftIO ioA = GhcT $ \_ -> liftIO ioA
instance ExceptionMonad m => ExceptionMonad (GhcT m) where
gcatch act handle =
GhcT $ \s -> unGhcT act s `gcatch` \e -> unGhcT (handle e) s
gmask f =
GhcT $ \s -> gmask $ \io_restore ->
let
g_restore (GhcT m) = GhcT $ \s -> io_restore (m s)
in
unGhcT (f g_restore) s
instance MonadIO m => HasDynFlags (GhcT m) where
getDynFlags = GhcT $ \(Session r) -> liftM hsc_dflags (liftIO $ readIORef r)
instance ExceptionMonad m => GhcMonad (GhcT m) where
getSession = GhcT $ \(Session r) -> liftIO $ readIORef r
setSession s' = GhcT $ \(Session r) -> liftIO $ writeIORef r s'
-- | Print the error message and all warnings. Useful inside exception
-- handlers. Clears warnings after printing.
printException :: GhcMonad m => SourceError -> m ()
printException err = do
dflags <- getSessionDynFlags
liftIO $ printBagOfErrors dflags (srcErrorMessages err)
-- | A function called to log warnings and errors.
type WarnErrLogger = forall m. GhcMonad m => Maybe SourceError -> m ()
defaultWarnErrLogger :: WarnErrLogger
defaultWarnErrLogger Nothing = return ()
defaultWarnErrLogger (Just e) = printException e
|
