Add --env-file flag

main/Main.hs

@@ -98,6 +98,8 @@ parseKernelArgs = foldl' addFlag defaultKernelSpecOptions
       kernelSpecOpts { kernelSpecInstallPrefix = Just prefix }
     addFlag kernelSpecOpts KernelspecUseStack =
       kernelSpecOpts { kernelSpecUseStack = True }
+    addFlag kernelSpecOpts (KernelspecEnvFile fp) =
+      kernelSpecOpts { kernelSpecEnvFile = Just fp }
     addFlag _kernelSpecOpts flag = error $ "Unknown flag" ++ show flag
 
 -- | Run the IHaskell language kernel.
@@ -127,13 +129,12 @@ runKernel kOpts profileSrc = do
 
     -- If we're in a stack directory, use `stack` to set the environment
     -- We can't do this with base <= 4.6 because setEnv doesn't exist.
-    when stack $ do
-      stackEnv <- lines <$> readProcess "stack" ["exec", "env"] ""
-      forM_ stackEnv $ \line ->
-        let (var, val) = break (== '=') line
-        in case tailMay val of
-            Nothing -> return ()
-            Just val' -> setEnv var val'
+    when stack $
+      readProcess "stack" ["exec", "env"] "" >>= parseAndSetEnv
+
+  case kernelSpecEnvFile kOpts of
+    Nothing -> return ()
+    Just envFile -> readFile envFile >>= parseAndSetEnv
 
   -- Serve on all sockets and ports defined in the profile.
   interface <- serveProfile profile debug
@@ -210,6 +211,12 @@ runKernel kOpts profileSrc = do
 
     isCommMessage req = mhMsgType (header req) `elem` [CommDataMessage, CommCloseMessage]
 
+    parseAndSetEnv envLines =
+      forM_ (lines envLines) $ \line -> do
+        case break (== '=') line of
+          (_, []) -> return ()
+          (key, _:val) -> setEnv key val
+
 -- Initial kernel state.
 initialKernelState :: IO (MVar KernelState)
 initialKernelState = newMVar defaultKernelState

src/IHaskell/Flags.hs

@@ -39,6 +39,7 @@ data Argument = ConfFile String     -- ^ A file with commands to load at startup
               | ConvertLhsStyle (LhsStyle String)
               | KernelspecInstallPrefix String
               | KernelspecUseStack
+              | KernelspecEnvFile FilePath
   deriving (Eq, Show)
 
 data LhsStyle string =
@@ -124,6 +125,14 @@ kernelStackFlag = flagNone ["stack"] addStack
   where
     addStack (Args md prev) = Args md (KernelspecUseStack : prev)
 
+kernelEnvFileFlag :: Flag Args
+kernelEnvFileFlag =
+  flagReq
+    ["env-file"]
+    (store KernelspecEnvFile)
+    "<file>"
+    "Load environment from this file when kernel is installed"
+
 confFlag :: Flag Args
 confFlag = flagReq ["conf", "c"] (store ConfFile) "<rc.hs>"
              "File with commands to execute at start; replaces ~/.ihaskell/rc.hs."
@@ -144,11 +153,11 @@ store constructor str (Args md prev) = Right $ Args md $ constructor str : prev
 installKernelSpec :: Mode Args
 installKernelSpec =
   mode "install" (Args InstallKernelSpec []) "Install the Jupyter kernelspec." noArgs
-    [ghcLibFlag, ghcRTSFlag, kernelDebugFlag, confFlag, installPrefixFlag, helpFlag, kernelStackFlag]
+    [ghcLibFlag, ghcRTSFlag, kernelDebugFlag, confFlag, installPrefixFlag, helpFlag, kernelStackFlag, kernelEnvFileFlag]
 
 kernel :: Mode Args
 kernel = mode "kernel" (Args (Kernel Nothing) []) "Invoke the IHaskell kernel." kernelArg
-           [ghcLibFlag, kernelDebugFlag, confFlag, kernelStackFlag, kernelCodeMirrorFlag]
+           [ghcLibFlag, kernelDebugFlag, confFlag, kernelStackFlag, kernelEnvFileFlag, kernelCodeMirrorFlag]
   where
     kernelArg = flagArg update "<json-kernel-file>"
     update filename (Args _ flags) = Right $ Args (Kernel $ Just filename) flags

src/IHaskell/IPython.hs

@@ -43,6 +43,7 @@ data KernelSpecOptions =
          , kernelSpecConfFile :: IO (Maybe String) -- ^ Filename of profile JSON file.
          , kernelSpecInstallPrefix :: Maybe String
          , kernelSpecUseStack :: Bool              -- ^ Whether to use @stack@ environments.
+         , kernelSpecEnvFile :: Maybe FilePath
          }
 
 defaultKernelSpecOptions :: KernelSpecOptions
@@ -55,6 +56,7 @@ defaultKernelSpecOptions = KernelSpecOptions
   , kernelSpecConfFile = defaultConfFile
   , kernelSpecInstallPrefix = Nothing
   , kernelSpecUseStack = False
+  , kernelSpecEnvFile = Nothing
   }
 
 -- | The IPython kernel name.