Invert the dependency between ghcide and hls-plugin-api

This PR includes changes both to ghcide and HLS to implement the reorg described in https://github.com/haskell/ghcide/issues/936#issuecomment-751437853

To summarise:

- `hls-plugin-api` no longer depends on ghcide.
- `ghcide` now depends on `hls-plugin-api` and exposes:
  - The ghcide HLS plugin
  - The `asGhcIdePlugin` adaptor

The goals are:
- to be able to break the `ghcide` HLS plugin down
- to rewrite exe:ghcide on top of the HLS plugin model.

The ghcide side is reviewed in haskell/ghcide#963

If this change is accepted there are two further considerations:
- This would be a good moment to merge the 2 repos, so that there is no history loss.
- `hls-plugin-api` will need to be released to Hackage prior to merging haskell/ghcide#963

exe/Plugins.hs

@@ -3,12 +3,13 @@
 module Plugins where
 
 import           Ide.Types                 (IdePlugins)
-import           Ide.Plugin                (pluginDescToIdePlugins)
+import           Ide.PluginUtils           (pluginDescToIdePlugins)
 
 -- fixed plugins
 import           Ide.Plugin.Example        as Example
 import           Ide.Plugin.Example2       as Example2
-import           Ide.Plugin.GhcIde         as GhcIde
+import           Development.IDE           (IdeState)
+import           Development.IDE.Plugin.HLS.GhcIde as GhcIde
 
 -- haskell-language-server optional plugins
 
@@ -73,7 +74,7 @@ import           Ide.Plugin.Brittany       as Brittany
 -- These can be freely added or removed to tailor the available
 -- features of the server.
 
-idePlugins :: Bool -> IdePlugins
+idePlugins :: Bool -> IdePlugins IdeState
 idePlugins includeExamples = pluginDescToIdePlugins allPlugins
   where
     allPlugins = if includeExamples

ghcide/ghcide.cabal

@@ -56,6 +56,8 @@ library
         haskell-lsp-types == 0.22.*,
         haskell-lsp == 0.22.*,
         hie-compat,
+        hls-plugin-api,
+        lens,
         mtl,
         network-uri,
         parallel,
@@ -127,7 +129,6 @@ library
         include
     exposed-modules:
         Development.IDE
-        Development.IDE.Compat
         Development.IDE.Core.Debouncer
         Development.IDE.Core.FileStore
         Development.IDE.Core.IdeConfiguration
@@ -163,6 +164,8 @@ library
         Development.IDE.Plugin
         Development.IDE.Plugin.Completions
         Development.IDE.Plugin.CodeAction
+        Development.IDE.Plugin.HLS
+        Development.IDE.Plugin.HLS.GhcIde
         Development.IDE.Plugin.Test
 
     -- Unfortunately, we cannot use loadSession with ghc-lib since hie-bios uses
@@ -190,6 +193,7 @@ library
         Development.IDE.Plugin.CodeAction.RuleTypes
         Development.IDE.Plugin.Completions.Logic
         Development.IDE.Plugin.Completions.Types
+        Development.IDE.Plugin.HLS.Formatter
         Development.IDE.Types.Action
     ghc-options: -Wall -Wno-name-shadowing -Wincomplete-uni-patterns
 

ghcide/src/Development/IDE.hs

@@ -9,6 +9,7 @@ module Development.IDE
 import Development.IDE.Core.RuleTypes as X
 import Development.IDE.Core.Rules as X
   (getAtPoint
+  ,getClientConfigAction
   ,getDefinition
   ,getParsedModule
   ,getTypeDefinition

ghcide/src/Development/IDE/Core/IdeConfiguration.hs

@@ -88,4 +88,4 @@ isWorkspaceFile file =
           workspaceFolders
 
 getClientSettings :: Action (Maybe Value)
-getClientSettings = unhashed . clientSettings <$> getIdeConfiguration
+getClientSettings = unhashed . clientSettings <$> getIdeConfiguration

ghcide/src/Development/IDE/Core/Rules.hs

@@ -27,11 +27,14 @@ module Development.IDE.Core.Rules(
     highlightAtPoint,
     getDependencies,
     getParsedModule,
+    getClientConfigAction,
     ) where
 
 import Fingerprint
 
+import Data.Aeson (fromJSON, Result(Success), FromJSON)
 import Data.Binary hiding (get, put)
+import Data.Default
 import Data.Tuple.Extra
 import Control.Monad.Extra
 import Control.Monad.Trans.Class
@@ -890,6 +893,15 @@ getClientSettingsRule = defineEarlyCutOffNoFile $ \GetClientSettings -> do
   settings <- clientSettings <$> getIdeConfiguration
   return (BS.pack . show . hash $ settings, settings)
 
+-- | Returns the client configurarion stored in the IdeState.
+-- You can use this function to access it from shake Rules
+getClientConfigAction :: (Default a, FromJSON a) => Action a
+getClientConfigAction = do
+  mbVal <- unhashed <$> useNoFile_ GetClientSettings
+  case fromJSON <$> mbVal of
+    Just (Success c) -> return c
+    _ -> return def
+
 -- | For now we always use bytecode
 getLinkableType :: NormalizedFilePath -> Action (Maybe LinkableType)
 getLinkableType f = do

ghcide/src/Development/IDE/Plugin.hs

@@ -1,14 +1,17 @@
-
-module Development.IDE.Plugin(Plugin(..), codeActionPlugin, codeActionPluginWithRules,makeLspCommandId,getPid) where
+module Development.IDE.Plugin
+  ( Plugin(..)
+  , codeActionPlugin
+  , codeActionPluginWithRules
+  , makeLspCommandId
+  ) where
 
 import Data.Default
 import qualified Data.Text as T
 import Development.Shake
 import Development.IDE.LSP.Server
-
-import           Language.Haskell.LSP.Types
-import Development.IDE.Compat
 import Development.IDE.Core.Rules
+import Ide.PluginUtils
+import           Language.Haskell.LSP.Types
 import qualified Language.Haskell.LSP.Core as LSP
 import Language.Haskell.LSP.Messages
 
@@ -50,11 +53,5 @@ codeActionPluginWithRules rr f = Plugin rr $ PartialHandlers $ \WithMessage{..}
 --   on that.
 makeLspCommandId :: T.Text -> IO T.Text
 makeLspCommandId command = do
-    pid <- getPid
-    return $ pid <> ":ghcide:" <> command
-
--- | Get the operating system process id for the running server
--- instance. This should be the same for the lifetime of the instance,
--- and different from that of any other currently running instance.
-getPid :: IO T.Text
-getPid = T.pack . show <$> getProcessID
+    pid <- getProcessID
+    return $ T.pack (show pid) <> ":ghcide:" <> command