From 5206857e0240940f17fba05851098dbedee70cac Mon Sep 17 00:00:00 2001
From: Anton-Latukha <anton.latukha@gmail.com>
Date: Sun, 11 Oct 2020 02:16:11 +0300
Subject: [PATCH] WIP

M  exe/Wrapper.hs
M  src/Ide/Version.hs
---
 exe/Wrapper.hs     | 20 +++++++++++++++++---
 src/Ide/Version.hs |  1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/exe/Wrapper.hs b/exe/Wrapper.hs
index 61dc26cd99..eda47fc075 100644
--- a/exe/Wrapper.hs
+++ b/exe/Wrapper.hs
@@ -1,6 +1,4 @@
 {-# LANGUAGE RecordWildCards #-}
--- | This module is based on the hie-wrapper.sh script in
--- https://github.com/alanz/vscode-hie-server
 module Main where
 
 import Control.Monad.Extra
@@ -42,9 +40,25 @@ main = do
       VersionMode PrintNumericVersion ->
           putStrLn haskellLanguageServerNumericVersion
 
+      NixMode nixModeArgs -> loadNixEnv nixArgs
+
       LspMode lspArgs ->
           launchHaskellLanguageServer lspArgs
 
+loadNixEnv :: NixArguments -> IO ()
+loadNixEnv nixModeArgs = do
+  s <- doesFileExist $ "shell.nix"
+  if s then loadNixShell s else do
+    d <- doesFileExist $ "default.nix"
+    if d then loadNixShell d else do
+      die $ "Nix environment requires `shell.nix` or `default.nix`, but none of them was found. Nix environment can be bootstrapped by `cabal2nix --shell . > default.nix`."
+ where
+  loadNixShell nixModeArgs = do
+    nixShell <- findExecutable "nix-shell"
+    case nixShell of
+      Nothing -> die $ "`--nix` option was provided, which requires `nix-shell` to load Nix enviroment, but this executable was not found."
+      Just nsexe -> callProcess nsexe nixModArgs
+
 launchHaskellLanguageServer :: LspArguments -> IO ()
 launchHaskellLanguageServer LspArguments{..} = do
   whenJust argsCwd setCurrentDirectory
@@ -104,6 +118,7 @@ getRuntimeGhcVersion' cradle = do
   case actionName (cradleOptsProg cradle) of
     Stack   -> checkToolExists "stack"
     Cabal   -> checkToolExists "cabal"
+    Nix     -> checkToolExists "nix"
     Default -> checkToolExists "ghc"
     Direct  -> checkToolExists "ghc"
     _       -> pure ()
@@ -143,4 +158,3 @@ findLocalCradle fp = do
     Nothing -> loadImplicitCradle fp
   hPutStrLn stderr $ "Module \"" ++ fp ++ "\" is loaded by Cradle: " ++ show crdl
   return crdl
-
diff --git a/src/Ide/Version.hs b/src/Ide/Version.hs
index 61b45fe3fa..ee732a2f03 100644
--- a/src/Ide/Version.hs
+++ b/src/Ide/Version.hs
@@ -54,6 +54,7 @@ findProgramVersions :: IO ProgramsOfInterest
 findProgramVersions = ProgramsOfInterest
   <$> findVersionOf "cabal"
   <*> findVersionOf "stack"
+  <*> findVersionOf "nix"
   <*> findVersionOf "ghc"
 
 -- | Find the version of the given program.