Add --ide flag (#1668)

* Add --ide flag to the Demo

* Fix things in the .cabal file

* Add tracing messages to Demo.hs

compiler/haskell-ide-core/haskell-ide-core.cabal

@@ -22,10 +22,12 @@ library
     default-language:   Haskell2010
     build-depends:
         aeson,
+        async,
         base == 4.*,
         binary,
         bytestring,
         containers,
+        data-default,
         deepseq,
         directory,
         either,
@@ -38,6 +40,7 @@ library
         haskell-lsp,
         haskell-lsp-types,
         mtl,
+        network-uri,
         pretty,
         rope-utf16-splay,
         safe-exceptions,
@@ -87,6 +90,11 @@ library
         Development.IDE.State.FileStore
         Development.IDE.State.Rules
         Development.IDE.Compat
+        Development.IDE.LSP.LanguageServer
+        Development.IDE.LSP.Definition
+        Development.IDE.LSP.Hover
+        Development.IDE.LSP.Protocol
+        Development.IDE.LSP.Server
         Development.IDE.Types.Options
         Development.IDE.State.RuleTypes
         Development.IDE.State.Service

compiler/haskell-ide-core/test/Demo.hs

@@ -36,7 +36,7 @@ import GHC.Paths
 
 main :: IO ()
 main = do
-    (ghcOptions, map toNormalizedFilePath -> files) <- getCmdLine
+    (ghcOptions, map toNormalizedFilePath -> files, isIde) <- getCmdLine
 
     -- lock to avoid overlapping output on stdout
     lock <- newLock
@@ -52,8 +52,10 @@ main = do
             ,optShakeProfiling = Nothing -- Just "output.html"
             }
 
-    if null files then
-        runLanguageServer logger $ \event vfs ->
+    if isIde then do
+        putStrLn "Starting IDE server"
+        runLanguageServer logger $ \event vfs -> do
+            putStrLn "Server started"
             initialise mainRule event logger options vfs
     else do
         vfs <- makeVFSHandle
@@ -92,16 +94,17 @@ newSession flags = runGhc (Just libdir) $ do
 
 
 -- | Convert the command line into GHC options and files to load.
-getCmdLine :: IO ([String], [FilePath])
+getCmdLine :: IO ([String], [FilePath], Bool)
 getCmdLine = do
     args <- getArgs
-    args <- return $ if null args then [".ghci"] else args
+    let isIde = "--ide" `elem` args
+    args <- return $ delete "--ide" $ if null args then [".ghci"] else args
     let (flags, files) = partition ("-" `isPrefixOf`) args
     let (ghci, hs) = partition ((==) ".ghci" . takeExtension) files
     (flags, files) <- both concat . unzip . ((flags,hs):) <$> mapM readGhci ghci
     when (null files) $
         fail "Expected some files to load, but didn't find any"
-    return (flags, files)
+    return (flags, files, isIde)
 
 readGhci :: FilePath -> IO ([String], [FilePath])
 readGhci file = do