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.

- ban load functions from GHC driver

- Enable CI for hls-eval-plugin and fix a bug due to clearing of mi_globals

Author: mpickering

.github/workflows/test.yml

@@ -148,7 +148,7 @@ jobs:
         name: Test hls-pragmas-plugin
         run: cabal test hls-pragmas-plugin --test-options="$TEST_OPTS" || LSP_TEST_LOG_COLOR=0 LSP_TEST_LOG_MESSAGES=true LSP_TEST_LOG_STDERR=true cabal test hls-pragmas-plugin --test-options="$TEST_OPTS"
 
-      - if: matrix.test && matrix.ghc != '9.4.4'
+      - if: matrix.test
         name: Test hls-eval-plugin
         run: cabal test hls-eval-plugin --test-options="$TEST_OPTS" || LSP_TEST_LOG_COLOR=0 LSP_TEST_LOG_MESSAGES=true LSP_TEST_LOG_STDERR=true cabal test hls-eval-plugin --test-options="$TEST_OPTS"
 

.hlint.yaml

@@ -208,6 +208,16 @@
   - name: "GHC.Arr.!"
     within: []
 
+  # We do not want to use functions from the
+  # GHC driver. Instead use hls rules to construct
+  # an appropriate GHC session
+  - name: "load"
+    within: []
+  - name: "load'"
+    within: []
+  - name: "loadWithCache"
+    within: []
+
   # Tracing functions
   # We ban an explicit list rather than the
   # Debug.Trace, because that module also

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

@@ -1008,28 +1008,6 @@ 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

@@ -104,6 +104,7 @@ module Development.IDE.GHC.Compat(
     icInteractiveModule,
     HomePackageTable,
     lookupHpt,
+    loadModulesHome,
 #if MIN_VERSION_ghc(9,3,0)
     Dependencies(dep_direct_mods),
 #else
@@ -653,3 +654,26 @@ 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 -> 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

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

@@ -874,7 +874,7 @@ pattern ExposePackage s a mr = DynFlags.ExposePackage s a mr
 pattern FunTy :: Type -> Type -> Type
 pattern FunTy arg res <- TyCoRep.FunTy {ft_arg = arg, ft_res = res}
 
-#if MIN_VERSION_ghc(9,0,0)
+#if MIN_VERSION_ghc(8,10,0)
 -- type HasSrcSpan x a = (GenLocated SrcSpan a ~ x)
 -- type HasSrcSpan x = () :: Constraint
 

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

@@ -20,6 +20,13 @@ module Development.IDE.GHC.Compat.Outputable (
 #if MIN_VERSION_ghc(9,3,0)
     DiagnosticReason(..),
     renderDiagnosticMessageWithHints,
+    pprMsgEnvelopeBagWithLoc,
+    Error.getMessages,
+    renderWithContext,
+    defaultSDocContext,
+    errMsgDiagnostic,
+    unDecorated,
+    diagnosticMessage,
 #else
     pprWarning,
     pprError,
@@ -29,6 +36,7 @@ module Development.IDE.GHC.Compat.Outputable (
     MsgEnvelope,
     ErrMsg,
     WarnMsg,
+    SourceError(..),
     errMsgSpan,
     errMsgSeverity,
     formatErrorWithQual,

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