+-- | These functions are called in various places of the GHC API.
+--
+-- API clients can override any of these callbacks to change GHC's default
+-- behaviour.
+data GhcApiCallbacks
+ = GhcApiCallbacks {
+
+ -- | Called by 'load' after the compilating of each module.
+ --
+ -- The default implementation simply prints all warnings and errors to
+ -- @stderr@. Don't forget to call 'clearWarnings' when implementing your
+ -- own call.
+ --
+ -- The first argument is the module that was compiled.
+ --
+ -- The second argument is @Nothing@ if no errors occured, but there may
+ -- have been warnings. If it is @Just err@ at least one error has
+ -- occured. If 'srcErrorMessages' is empty, compilation failed due to
+ -- @-Werror@.
+ reportModuleCompilationResult :: GhcMonad m =>
+ ModSummary -> Maybe SourceError
+ -> m ()
+ }
+
+-- | Temporarily modify the callbacks. After the action is executed all
+-- callbacks are reset (not, however, any other modifications to the session
+-- state.)
+withLocalCallbacks :: GhcMonad m =>
+ (GhcApiCallbacks -> GhcApiCallbacks)
+ -> m a -> m a
+withLocalCallbacks f m = do
+ hsc_env <- getSession
+ let cb0 = hsc_callbacks hsc_env
+ let cb' = f cb0
+ setSession (hsc_env { hsc_callbacks = cb' `seq` cb' })
+ r <- m
+ hsc_env' <- getSession
+ setSession (hsc_env' { hsc_callbacks = cb0 })
+ return r
+
+\end{code}
+
+\begin{code}
+-- | Hscenv is like 'Session', except that some of the fields are immutable.