Remove IsHiFileStable rule and use the previous version to approximate it.

The SourceUnmodifiedAndStable check in loadInterface wasn't doing much for us
because we use bytecode and there is no bytecode on disk so we always had to
recompile.

Author: wz1000

ghcide/src/Development/IDE.hs

@@ -17,8 +17,7 @@ import           Development.IDE.Core.IdeConfiguration as X (IdeConfiguration (.
                                                              isWorkspaceFile)
 import           Development.IDE.Core.OfInterest       as X (getFilesOfInterestUntracked)
 import           Development.IDE.Core.RuleTypes        as X
-import           Development.IDE.Core.Rules            as X (IsHiFileStable (..),
-                                                             getClientConfigAction,
+import           Development.IDE.Core.Rules            as X (getClientConfigAction,
                                                              getParsedModule)
 import           Development.IDE.Core.Service          as X (runAction)
 import           Development.IDE.Core.Shake            as X (FastResult (..),

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

@@ -30,7 +30,6 @@ module Development.IDE.Core.Rules(
     usePropertyAction,
     -- * Rules
     CompiledLinkables(..),
-    IsHiFileStable(..),
     getParsedModuleRule,
     getParsedModuleWithCommentsRule,
     getLocatedImportsRule,
@@ -42,7 +41,6 @@ module Development.IDE.Core.Rules(
     getModIfaceFromDiskRule,
     getModIfaceRule,
     getModSummaryRule,
-    isHiFileStableRule,
     getModuleGraphRule,
     knownFilesRule,
     getClientSettingsRule,
@@ -121,7 +119,6 @@ import           Development.IDE.GHC.ExactPrint hiding (LogShake, Log)
 import           Development.IDE.GHC.Util                     hiding
                                                               (modifyDynFlags)
 import           Development.IDE.Graph
-import           Development.IDE.Graph.Classes
 import           Development.IDE.Import.DependencyInformation
 import           Development.IDE.Import.FindImports
 import qualified Development.IDE.Spans.AtPoint                as AtPoint
@@ -131,7 +128,6 @@ import           Development.IDE.Types.Diagnostics            as Diag
 import           Development.IDE.Types.HscEnvEq
 import           Development.IDE.Types.Location
 import           Development.IDE.Types.Options
-import           GHC.Generics                                 (Generic)
 import qualified GHC.LanguageExtensions                       as LangExt
 import qualified HieDb
 import           Ide.Plugin.Config
@@ -156,6 +152,7 @@ import Development.IDE.Types.Logger (Recorder, logWith, cmapWithPrio, WithPriori
 import qualified Development.IDE.Core.Shake as Shake
 import qualified Development.IDE.GHC.ExactPrint as ExactPrint hiding (LogShake)
 import qualified Development.IDE.Types.Logger as Logger
+import qualified Development.IDE.Types.Shake as Shake
 
 data Log 
   = LogShake Shake.Log
@@ -773,14 +770,18 @@ ghcSessionDepsDefinition fullModSummary GhcSessionDepsConfig{..} env file = do
 -- | Load a iface from disk, or generate it if there isn't one or it is out of date
 -- This rule also ensures that the `.hie` and `.o` (if needed) files are written out.
 getModIfaceFromDiskRule :: Recorder (WithPriority Log) -> Rules ()
-getModIfaceFromDiskRule recorder = defineEarlyCutoff (cmapWithPrio LogShake recorder) $ Rule $ \GetModIfaceFromDisk f -> do
+getModIfaceFromDiskRule recorder = defineEarlyCutoff (cmapWithPrio LogShake recorder) $ RuleWithOldValue $ \GetModIfaceFromDisk f old -> do
   ms <- msrModSummary <$> use_ GetModSummary f
   mb_session <- use GhcSessionDeps f
   case mb_session of
     Nothing -> return (Nothing, ([], Nothing))
     Just session -> do
-      sourceModified <- use_ IsHiFileStable f
       linkableType <- getLinkableType f
+      ver <- use_ GetModificationTime f
+      let sourceModified = case old of
+            Shake.Succeeded (Just old_version) _ | old_version == ver -> SourceUnmodified
+            Shake.Stale _   (Just old_version) _ | old_version == ver -> SourceUnmodified
+            _ -> SourceModified
       r <- loadInterface (hscEnv session) ms sourceModified linkableType (regenerateHiFile session f ms)
       case r of
         (diags, Nothing) -> return (Nothing, (diags, Nothing))
@@ -832,31 +833,6 @@ getModIfaceFromDiskAndIndexRule recorder =
 
   return (Just x)
 
-isHiFileStableRule :: Recorder (WithPriority Log) -> Rules ()
-isHiFileStableRule recorder = defineEarlyCutoff (cmapWithPrio LogShake recorder) $ RuleNoDiagnostics $ \IsHiFileStable f -> do
-    ms <- msrModSummary <$> use_ GetModSummaryWithoutTimestamps f
-    let hiFile = toNormalizedFilePath'
-                $ Compat.ml_hi_file $ ms_location ms
-    mbHiVersion <- use  GetModificationTime_{missingFileDiagnostics=False} hiFile
-    modVersion  <- use_ GetModificationTime f
-    sourceModified <- case mbHiVersion of
-        Nothing -> pure SourceModified
-        Just x ->
-            if modificationTime x < modificationTime modVersion
-                then pure SourceModified
-                else do
-                    fileImports <- use_ GetLocatedImports f
-                    let imports = fmap artifactFilePath . snd <$> fileImports
-                    deps <- uses_ IsHiFileStable (catMaybes imports)
-                    pure $ if all (== SourceUnmodifiedAndStable) deps
-                           then SourceUnmodifiedAndStable
-                           else SourceUnmodified
-    return (Just (summarize sourceModified), Just sourceModified)
-  where
-      summarize SourceModified            = BS.singleton 1
-      summarize SourceUnmodified          = BS.singleton 2
-      summarize SourceUnmodifiedAndStable = BS.singleton 3
-
 displayTHWarning :: LspT c IO ()
 displayTHWarning
   | not isWindows && not hostIsDynamic = do
@@ -1153,7 +1129,6 @@ mainRule recorder RulesConfig{..} = do
     getModIfaceFromDiskAndIndexRule recorder
     getModIfaceRule recorder
     getModSummaryRule recorder
-    isHiFileStableRule recorder
     getModuleGraphRule recorder
     knownFilesRule recorder
     getClientSettingsRule recorder
@@ -1175,13 +1150,3 @@ mainRule recorder RulesConfig{..} = do
     persistentHieFileRule recorder
     persistentDocMapRule
     persistentImportMapRule
-
--- | Given the path to a module src file, this rule returns True if the
--- corresponding `.hi` file is stable, that is, if it is newer
---   than the src file, and all its dependencies are stable too.
-data IsHiFileStable = IsHiFileStable
-    deriving (Eq, Show, Typeable, Generic)
-instance Hashable IsHiFileStable
-instance NFData   IsHiFileStable
-
-type instance RuleResult IsHiFileStable = SourceModified