Local hidir and hiedir folders to avoid conflicts with Cabal (#441)

* Local hidir and hiedir folders to avoid conflicts with Cabal

hi files created by ghcide would have different optimization settings,
triggering Cabal recompilation if they were stored in Cabal folders

hie files would end up in the src folder as -hiedir is not set by Cabal

Telling GHC to write interface/hie files is pointless since we do it ourselves,
and it also leads to the recompilation checker getting confused

Using hie-bios initSession does things like setting up the cache directory for
interface files and other things which ghcide would rather manage itself.

* linker options

Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>

exe/Main.hs

@@ -19,6 +19,9 @@ import Control.DeepSeq (NFData)
 import Control.Exception
 import Control.Monad.Extra
 import Control.Monad.IO.Class
+import qualified Crypto.Hash.SHA1 as H
+import qualified Data.ByteString.Char8 as B
+import Data.ByteString.Base16
 import Data.Default
 import System.Time.Extra
 import Development.IDE.Core.Debouncer
@@ -57,15 +60,28 @@ import qualified Data.Map.Strict as Map
 import GHC hiding (def)
 import GHC.Generics (Generic)
 import qualified GHC.Paths
+import           DynFlags
 
+import HIE.Bios.Environment
 import HIE.Bios
 import HIE.Bios.Cradle
 import HIE.Bios.Types
 
+-- Prefix for the cache path
+cacheDir :: String
+cacheDir = "ghcide"
+
 -- Set the GHC libdir to the nix libdir if it's present.
 getLibdir :: IO FilePath
 getLibdir = fromMaybe GHC.Paths.libdir <$> lookupEnv "NIX_GHC_LIBDIR"
 
+getCacheDir :: [String] -> IO FilePath
+getCacheDir opts = IO.getXdgDirectory IO.XdgCache (cacheDir </> opts_hash)
+    where
+        -- Create a unique folder per set of different GHC options, assuming that each different set of
+        -- GHC options will create incompatible interface files.
+        opts_hash = B.unpack $ encode $ H.finalize $ H.updates H.init (map B.pack opts)
+
 ghcideVersion :: IO String
 ghcideVersion = do
   path <- getExecutablePath
@@ -224,14 +240,50 @@ getComponentOptions cradle = do
 
 
 createSession :: ComponentOptions -> IO HscEnvEq
-createSession opts = do
+createSession (ComponentOptions theOpts _) = do
     libdir <- getLibdir
+
+    cacheDir <- Main.getCacheDir theOpts
+
     env <- runGhc (Just libdir) $ do
-        _targets <- initSession opts
+        dflags <- getSessionDynFlags
+        (dflags', _targets) <- addCmdOpts theOpts dflags
+        _ <- setSessionDynFlags $
+             -- disabled, generated directly by ghcide instead
+             flip gopt_unset Opt_WriteInterface $
+             -- disabled, generated directly by ghcide instead
+             -- also, it can confuse the interface stale check
+             dontWriteHieFiles $
+             setHiDir cacheDir $
+             setDefaultHieDir cacheDir $
+             setIgnoreInterfacePragmas $
+             setLinkerOptions $
+             disableOptimisation dflags'
         getSession
     initDynLinker env
     newHscEnvEq env
 
+-- we don't want to generate object code so we compile to bytecode
+-- (HscInterpreted) which implies LinkInMemory
+-- HscInterpreted
+setLinkerOptions :: DynFlags -> DynFlags
+setLinkerOptions df = df {
+    ghcLink   = LinkInMemory
+  , hscTarget = HscNothing
+  , ghcMode = CompManager
+  }
+
+setIgnoreInterfacePragmas :: DynFlags -> DynFlags
+setIgnoreInterfacePragmas df =
+    gopt_set (gopt_set df Opt_IgnoreInterfacePragmas) Opt_IgnoreOptimChanges
+
+disableOptimisation :: DynFlags -> DynFlags
+disableOptimisation df = updOptLevel 0 df
+
+setHiDir :: FilePath -> DynFlags -> DynFlags
+setHiDir f d =
+    -- override user settings to avoid conflicts leading to recompilation
+    d { hiDir      = Just f}
 
 cradleToSession :: Maybe FilePath -> Cradle a -> Action HscEnvEq
 cradleToSession mbYaml cradle = do

ghcide.cabal

@@ -171,7 +171,10 @@ executable ghcide
         hslogger,
         base == 4.*,
         binary,
+        base16-bytestring >=0.1.1 && <0.2,
+        bytestring,
         containers,
+        cryptohash-sha1 >=0.11.100 && <0.12,
         data-default,
         deepseq,
         directory,

src/Development/IDE/GHC/Compat.hs

@@ -12,6 +12,8 @@ module Development.IDE.GHC.Compat(
     mkHieFile,
     writeHieFile,
     readHieFile,
+    setDefaultHieDir,
+    dontWriteHieFiles,
     hPutStringBuffer,
     includePathsGlobal,
     includePathsQuote,
@@ -156,3 +158,19 @@ pattern IEThingAll a <-
 #else
     GHC.IEThingAll a
 #endif
+
+setDefaultHieDir :: FilePath -> DynFlags -> DynFlags
+setDefaultHieDir _f d =
+#if MIN_GHC_API_VERSION(8,8,0)
+    d { hieDir     = hieDir d `mappend` Just _f}
+#else
+    d
+#endif
+
+dontWriteHieFiles :: DynFlags -> DynFlags
+dontWriteHieFiles d =
+#if MIN_GHC_API_VERSION(8,8,0)
+    gopt_unset d Opt_WriteHie
+#else
+    d
+#endif

src/Development/IDE/GHC/Util.hs

@@ -19,6 +19,8 @@ module Development.IDE.GHC.Util(
     textToStringBuffer,
     readFileUtf8,
     hDuplicateTo',
+    setDefaultHieDir,
+    dontWriteHieFiles
     ) where
 
 import Control.Concurrent
@@ -27,7 +29,6 @@ import Data.Maybe
 import Data.Typeable
 import qualified Data.ByteString.Internal as BS
 import Fingerprint
-import GHC
 import GhcMonad
 import GhcPlugins hiding (Unique)
 import Data.IORef
@@ -52,6 +53,7 @@ import Lexer
 import StringBuffer
 import System.FilePath
 
+import Development.IDE.GHC.Compat as GHC
 import Development.IDE.Types.Location