Simplify implementation of eval plugin and make it work with GHC 9.4

The plugin was implemented by calling "load" which circumvents all of
HLSs caching mechanisms for interface files and linkables. Instead we
should work like the other typechecking functions which get all the
stuff we need using HLS rules and setup the HscEnv with all the state in
the right places.

The key part to this is setting up all the HPT modules with linkables if
they are depenedencies of the module we are trying to run a function
from.

Author: mpickering

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

@@ -984,28 +984,6 @@ handleGenerationErrors' dflags source action =
     . (("Error during " ++ T.unpack source) ++) . show @SomeException
     ]
 
--- | Load modules, quickly. Input doesn't need to be desugared.
--- A module must be loaded before dependent modules can be typechecked.
--- This variant of loadModuleHome will *never* cause recompilation, it just
--- modifies the session.
--- The order modules are loaded is important when there are hs-boot files.
--- In particular you should make sure to load the .hs version of a file after the
--- .hs-boot version.
-loadModulesHome
-    :: [HomeModInfo]
-    -> HscEnv
-    -> HscEnv
-loadModulesHome mod_infos e =
-#if MIN_VERSION_ghc(9,3,0)
-  hscUpdateHUG (\hug -> foldl' (flip addHomeModInfoToHug) hug mod_infos) (e { hsc_type_env_vars = emptyKnotVars })
-#else
-  let !new_modules = addListToHpt (hsc_HPT e) [(mod_name x, x) | x <- mod_infos]
-  in e { hsc_HPT = new_modules
-       , hsc_type_env_var = Nothing
-       }
-    where
-      mod_name = moduleName . mi_module . hm_iface
-#endif
 
 -- Merge the HPTs, module graphs and FinderCaches
 -- See Note [GhcSessionDeps] in Development.IDE.Core.Rules

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

@@ -57,6 +57,7 @@ module Development.IDE.Core.Rules(
     typeCheckRuleDefinition,
     getRebuildCount,
     getSourceFileSource,
+    currentLinkables,
     GhcSessionDepsConfig(..),
     Log(..),
     DisplayTHWarning(..),

ghcide/src/Development/IDE/GHC/Compat.hs

@@ -102,6 +102,7 @@ module Development.IDE.GHC.Compat(
     icInteractiveModule,
     HomePackageTable,
     lookupHpt,
+    loadModulesHome,
 #if MIN_VERSION_ghc(9,3,0)
     Dependencies(dep_direct_mods),
 #else
@@ -651,3 +652,26 @@ combineRealSrcSpans span1 span2
                                   (srcSpanEndLine span2, srcSpanEndCol span2)
     file = srcSpanFile span1
 #endif
+
+-- | Load modules, quickly. Input doesn't need to be desugared.
+-- A module must be loaded before dependent modules can be typechecked.
+-- This variant of loadModuleHome will *never* cause recompilation, it just
+-- modifies the session.
+-- The order modules are loaded is important when there are hs-boot files.
+-- In particular you should make sure to load the .hs version of a file after the
+-- .hs-boot version.
+loadModulesHome
+    :: [HomeModInfo]
+    -> HscEnv
+    -> HscEnv
+loadModulesHome mod_infos e =
+#if MIN_VERSION_ghc(9,3,0)
+  hscUpdateHUG (\hug -> foldr addHomeModInfoToHug hug mod_infos) (e { hsc_type_env_vars = emptyKnotVars })
+#else
+  let !new_modules = addListToHpt (hsc_HPT e) [(mod_name x, x) | x <- mod_infos]
+  in e { hsc_HPT = new_modules
+       , hsc_type_env_var = Nothing
+       }
+    where
+      mod_name = moduleName . mi_module . hm_iface
+#endif

ghcide/src/Development/IDE/GHC/Compat/Util.hs

@@ -24,9 +24,7 @@ module Development.IDE.GHC.Compat.Util (
     LBooleanFormula,
     BooleanFormula(..),
     -- * OverridingBool
-#if !MIN_VERSION_ghc(9,3,0)
     OverridingBool(..),
-#endif
     -- * Maybes
     MaybeErr(..),
     orElse,
@@ -104,6 +102,11 @@ import           Unique
 import           Util
 #endif
 
+#if MIN_VERSION_ghc(9,3,0)
+import           GHC.Data.Bool
+#endif
+
+
 #if !MIN_VERSION_ghc(9,0,0)
 type MonadCatch = Exception.ExceptionMonad
 

haskell-language-server.cabal

@@ -237,7 +237,7 @@ common haddockComments
     cpp-options: -Dhls_haddockComments
 
 common eval
-  if flag(eval) && (impl(ghc < 9.4.1) || flag(ignore-plugins-ghc-bounds))
+  if flag(eval)
     build-depends: hls-eval-plugin ^>= 1.4
     cpp-options: -Dhls_eval
 

plugins/hls-eval-plugin/hls-eval-plugin.cabal

@@ -37,10 +37,6 @@ source-repository head
   location: https://github.com/haskell/haskell-language-server
 
 library
-  if impl(ghc >= 9.3)
-    buildable: False
-  else
-    buildable: True
   exposed-modules:
     Ide.Plugin.Eval
     Ide.Plugin.Eval.Types
@@ -101,10 +97,6 @@ library
     TypeOperators
 
 test-suite tests
-  if impl(ghc >= 9.3)
-    buildable: False
-  else
-    buildable: True
   type:             exitcode-stdio-1.0
   default-language: Haskell2010
   hs-source-dirs:   test

plugins/hls-eval-plugin/src/Ide/Plugin/Eval/Code.hs

@@ -4,7 +4,7 @@
 {-# OPTIONS_GHC -Wwarn -fno-warn-orphans #-}
 
 -- | Expression execution
-module Ide.Plugin.Eval.Code (Statement, testRanges, resultRange, evalSetup, propSetup, testCheck, asStatements,myExecStmt) where
+module Ide.Plugin.Eval.Code (Statement, testRanges, resultRange, propSetup, testCheck, asStatements,myExecStmt) where
 
 import           Control.Lens                   ((^.))
 import           Control.Monad.IO.Class
@@ -80,12 +80,6 @@ asStmts (Property t _ _) =
     ["prop11 = " ++ t, "(propEvaluation prop11 :: IO String)"]
 
 
--- |GHC declarations required for expression evaluation
-evalSetup :: Ghc ()
-evalSetup = do
-    preludeAsP <- parseImportDecl "import qualified Prelude as P"
-    context <- getContext
-    setContext (IIDecl preludeAsP : context)
 
 -- | A wrapper of 'InteractiveEval.execStmt', capturing the execution result
 myExecStmt :: String -> ExecOptions -> Ghc (Either String (Maybe String))