Adding :m + and :m -. Closes #298.

src/IHaskell/Eval/Evaluate.hs

@@ -452,6 +452,22 @@ evalCommand output (Directive SetExtension opts) state = do
   let set = concatMap (" -X" ++) $ words opts
   evalCommand output (Directive SetDynFlag set) state
 
+evalCommand output (Directive LoadModule mods) state = wrapExecution state $ do
+  write $ "Load Module: " ++ mods
+  let stripped@(firstChar:remainder) = mods
+      (modules, removeModule) =
+        case firstChar of
+          '+' -> (words remainder, False)
+          '-' -> (words remainder, True)
+          _ -> (words stripped, False)
+
+  forM_ modules $ \modl ->
+    if removeModule
+    then removeImport modl
+    else evalImport $ "import " ++ modl
+
+  return mempty
+
 evalCommand a (Directive SetOption opts) state = do
   write $ "Option: " ++ opts
   let (existing, nonExisting) = partition optionExists $ words opts

src/IHaskell/Eval/Parser.hs

@@ -67,6 +67,7 @@ data DirectiveType
   | SearchHoogle    -- ^ Search for something via Hoogle.
   | GetDoc          -- ^ Get documentation for an identifier via Hoogle.
   | GetKind         -- ^ Get the kind of a type via ':kind'.
+  | LoadModule      -- ^ Load and unload modules via ':module'.
   deriving (Show, Eq)
 
 -- | Pragma types. Only LANGUAGE pragmas are currently supported.
@@ -268,7 +269,8 @@ parseDirective (':':directive) line = case find rightDirective directives of
       [] -> False
       dir:_ -> dir `elem` tail (inits dirname)
     directives =
-      [ (GetType,      "type")
+      [ (LoadModule,   "module")
+      , (GetType,      "type")
       , (GetKind,      "kind")
       , (GetInfo,      "info")
       , (SearchHoogle, "hoogle")

src/IHaskell/Eval/Util.hs

@@ -11,6 +11,7 @@ module IHaskell.Eval.Util (
 
   -- * Code Evaluation
   evalImport,
+  removeImport,
   evalDeclarations,
   getType,
   getDescription,
@@ -196,6 +197,18 @@ evalImport imports = do
                            Just (True, _) -> True
                            _ -> False
 
+removeImport :: GhcMonad m => String -> m ()
+removeImport moduleName = do
+  flags <- getSessionDynFlags
+  ctx <- getContext
+  let ctx' = filter (not . (isImportOf $ mkModuleName moduleName)) ctx
+  setContext ctx'
+
+  where
+    isImportOf :: ModuleName -> InteractiveImport -> Bool
+    isImportOf name (IIModule modName) = name == modName
+    isImportOf name (IIDecl impDecl) = name == unLoc (ideclName impDecl)
+
 -- | Evaluate a series of declarations.
 -- Return all names which were bound by these declarations.
 evalDeclarations :: GhcMonad m => String -> m [String]