```

Refactor session loading to handle pending files

Introduced a queue to manage pending files during session loading, ensuring that file options are processed in batches. This change improves the efficiency and reliability of session initialization by serializing file processing and avoiding redundant lookups.
```

ghcide/session-loader/Development/IDE/Session.hs

@@ -453,6 +453,7 @@ loadSessionWithOptions recorder SessionLoadingOptions{..} rootDir que = do
   -- you have to modify 'filesMap' as well.
   filesMap <- newVar HM.empty :: IO (Var FilesMap)
   -- Version of the mappings above
+  pendingFilesTQueue <- newTQueueIO
   version <- newVar 0
   biosSessionLoadingVar <- newVar Nothing :: IO (Var (Maybe SessionLoadingPreferenceConfig))
   let returnWithVersion fun = IdeGhcSession fun <$> liftIO (readVar version)
@@ -474,7 +475,6 @@ loadSessionWithOptions recorder SessionLoadingOptions{..} rootDir que = do
     let invalidateShakeCache = do
             void $ modifyVar' version succ
             return $ toNoFileKey GhcSessionIO
-    OfInterestVar filesOfInterVar <- getIdeGlobalAction
     IdeOptions{ optTesting = IdeTesting optTesting
               , optCheckProject = getCheckProject
               , optExtensions
@@ -728,31 +728,23 @@ loadSessionWithOptions recorder SessionLoadingOptions{..} rootDir que = do
             sessionOptsList yamlFiles
 
 
-
     -- The main function which gets options for a file. We only want one of these running
     -- at a time. Therefore the IORef contains the currently running cradle, if we try
     -- to get some more options then we wait for the currently running action to finish
     -- before attempting to do so.
-    -- let getOptions :: FilePath -> IO (IdeResult HscEnvEq, [FilePath])
-    --     getOptions file = do
-    --         let ncfp = toNormalizedFilePath' (toAbsolutePath file)
-    --         cachedHieYamlLocation <- HM.lookup ncfp <$> readVar filesMap
-    --         hieYaml <- cradleLoc file
-    --         sessionOpts (join cachedHieYamlLocation <|> hieYaml, file) `Safe.catch` \e ->
-    --             return (([renderPackageSetupException file e], Nothing), maybe [] pure hieYaml)
-
     let getOptionsBatch :: FilePath -> IO (IdeResult HscEnvEq, [FilePath])
         getOptionsBatch file' = do
+            pendingFiles <- atomically $ flushTQueue pendingFilesTQueue
             let file = toAbsolutePath file'
             hieYaml <- cradleLoc file
-            filesOfInterest <- HashMap.keys <$> readVar filesOfInterVar
             logWith recorder Debug LogSettingInitialDynFlags
-            results <- getOptionsList (Set.toList $ Set.fromList $ toAbsolutePath file : map fromNormalizedFilePath filesOfInterest)
+            results <- getOptionsList (Set.toList $ Set.fromList $ toAbsolutePath file : map fromNormalizedFilePath pendingFiles)
             return (results Map.! file) `Safe.catch` \e ->
                 return (([renderPackageSetupException file e], Nothing), maybe [] pure hieYaml)
 
     returnWithVersion $ \file -> do
       -- see Note [Serializing runs in separate thread]
+      atomically $ writeTQueue pendingFilesTQueue file
       awaitRunInThread que $ getOptionsBatch file
 
 -- cradleToType :: Cradle Void -> IO ()