Simplify package DB logic by removing GHC 7.6 compatibility layer

Cabal/src/Distribution/Simple/Configure.hs

@@ -2095,7 +2095,7 @@ getInstalledPackages verbosity comp mbWorkDir packageDBs progdb = do
   -- do not check empty packagedbs (ghc-pkg would error out)
   packageDBs' <- filterM packageDBExists packageDBs
   case compilerFlavor comp of
-    GHC -> GHC.getInstalledPackages verbosity comp mbWorkDir packageDBs' progdb
+    GHC -> GHC.getInstalledPackages verbosity mbWorkDir packageDBs' progdb
     GHCJS -> GHCJS.getInstalledPackages verbosity mbWorkDir packageDBs' progdb
     UHC -> UHC.getInstalledPackages verbosity comp mbWorkDir packageDBs' progdb
     flv ->

Cabal/src/Distribution/Simple/Errors.hs

@@ -96,8 +96,7 @@ data CabalException
   | AmbiguousBuildTarget [(String, [(String, String)])]
   | CheckBuildTargets String
   | VersionMismatchGHC FilePath Version FilePath Version
-  | CheckPackageDbStackPost76
-  | CheckPackageDbStackPre76
+  | CheckPackageDbStack
   | GlobalPackageDbSpecifiedFirst
   | CantInstallForeignLib
   | NoSupportForPreProcessingTest TestType
@@ -230,8 +229,8 @@ exceptionCode e = case e of
   AmbiguousBuildTarget{} -> 7865
   CheckBuildTargets{} -> 4733
   VersionMismatchGHC{} -> 4000
-  CheckPackageDbStackPost76{} -> 3000
-  CheckPackageDbStackPre76{} -> 5640
+  CheckPackageDbStack{} -> 3000
+  -- Retired: CheckPackageDbStackPre76{} -> 5640
   GlobalPackageDbSpecifiedFirst{} -> 2345
   CantInstallForeignLib{} -> 8221
   NoSupportForPreProcessingTest{} -> 3008
@@ -470,13 +469,9 @@ exceptionMessage e = case e of
       ++ ghcPkgProgPath
       ++ " is version "
       ++ prettyShow ghcPkgVersion
-  CheckPackageDbStackPost76 ->
+  CheckPackageDbStack ->
     "If the global package db is specified, it must be "
       ++ "specified first and cannot be specified multiple times"
-  CheckPackageDbStackPre76 ->
-    "With current ghc versions the global package db is always used "
-      ++ "and must be listed first. This ghc limitation is lifted in GHC 7.6,"
-      ++ "see https://gitlab.haskell.org/ghc/ghc/-/issues/5977"
   GlobalPackageDbSpecifiedFirst ->
     "If the global package db is specified, it must be "
       ++ "specified first and cannot be specified multiple times"

Cabal/src/Distribution/Simple/GHC.hs

@@ -489,14 +489,13 @@ getPackageDBContents verbosity mbWorkDir packagedb progdb = do
 -- | Given a package DB stack, return all installed packages.
 getInstalledPackages
   :: Verbosity
-  -> Compiler
   -> Maybe (SymbolicPath CWD (Dir from))
   -> PackageDBStackX (SymbolicPath from (Dir PkgDB))
   -> ProgramDb
   -> IO InstalledPackageIndex
-getInstalledPackages verbosity comp mbWorkDir packagedbs progdb = do
+getInstalledPackages verbosity mbWorkDir packagedbs progdb = do
   checkPackageDbEnvVar verbosity
-  checkPackageDbStack verbosity comp packagedbs
+  checkPackageDbStack verbosity packagedbs
   pkgss <- getInstalledPackages' verbosity mbWorkDir packagedbs progdb
   index <- toPackageIndex verbosity pkgss progdb
   return $! hackRtsPackage index
@@ -576,30 +575,13 @@ checkPackageDbEnvVar :: Verbosity -> IO ()
 checkPackageDbEnvVar verbosity =
   Internal.checkPackageDbEnvVar verbosity "GHC" "GHC_PACKAGE_PATH"
 
-checkPackageDbStack :: Eq fp => Verbosity -> Compiler -> PackageDBStackX fp -> IO ()
-checkPackageDbStack verbosity comp =
-  if flagPackageConf implInfo
-    then checkPackageDbStackPre76 verbosity
-    else checkPackageDbStackPost76 verbosity
-  where
-    implInfo = ghcVersionImplInfo (compilerVersion comp)
-
-checkPackageDbStackPost76 :: Eq fp => Verbosity -> PackageDBStackX fp -> IO ()
-checkPackageDbStackPost76 _ (GlobalPackageDB : rest)
+checkPackageDbStack :: Eq fp => Verbosity -> PackageDBStackX fp -> IO ()
+checkPackageDbStack _ (GlobalPackageDB : rest)
   | GlobalPackageDB `notElem` rest = return ()
-checkPackageDbStackPost76 verbosity rest
+checkPackageDbStack verbosity rest
   | GlobalPackageDB `elem` rest =
-      dieWithException verbosity CheckPackageDbStackPost76
-checkPackageDbStackPost76 _ _ = return ()
-
-checkPackageDbStackPre76 :: Eq fp => Verbosity -> PackageDBStackX fp -> IO ()
-checkPackageDbStackPre76 _ (GlobalPackageDB : rest)
-  | GlobalPackageDB `notElem` rest = return ()
-checkPackageDbStackPre76 verbosity rest
-  | GlobalPackageDB `notElem` rest =
-      dieWithException verbosity CheckPackageDbStackPre76
-checkPackageDbStackPre76 verbosity _ =
-  dieWithException verbosity GlobalPackageDbSpecifiedFirst
+      dieWithException verbosity CheckPackageDbStack
+checkPackageDbStack _ _ = return ()
 
 -- GHC < 6.10 put "$topdir/include/mingw" in rts's installDirs. This
 -- breaks when you want to use a different gcc, so we need to filter
@@ -710,7 +692,7 @@ startInterpreter verbosity progdb comp platform packageDBs = do
           { ghcOptMode = toFlag GhcModeInteractive
           , ghcOptPackageDBs = packageDBs
           }
-  checkPackageDbStack verbosity comp packageDBs
+  checkPackageDbStack verbosity packageDBs
   (ghcProg, _) <- requireProgram verbosity ghcProgram progdb
   -- This doesn't pass source file arguments to GHC, so we don't have to worry
   -- about using a response file here.

Cabal/src/Distribution/Simple/GHCJS.hs

@@ -750,23 +750,6 @@ buildOrReplLib mReplFlags verbosity numJobs _pkg_descr lbi lib clbi = do
     let stubObjs = []
         stubSharedObjs = []
 
-    {-
-        stubObjs <- catMaybes <$> sequenceA
-          [ findFileWithExtension [objExtension] [libTargetDir]
-              (ModuleName.toFilePath x ++"_stub")
-          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
-          , x <- allLibModules lib clbi ]
-        stubProfObjs <- catMaybes <$> sequenceA
-          [ findFileWithExtension ["p_" ++ objExtension] [libTargetDir]
-              (ModuleName.toFilePath x ++"_stub")
-          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
-          , x <- allLibModules lib clbi ]
-        stubSharedObjs <- catMaybes <$> sequenceA
-          [ findFileWithExtension ["dyn_" ++ objExtension] [libTargetDir]
-              (ModuleName.toFilePath x ++"_stub")
-          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
-          , x <- allLibModules lib clbi ]
-    -}
     hObjs <-
       Internal.getHaskellObjects
         implInfo

Cabal/src/Distribution/Simple/Program/GHC.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE MultiWayIf #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE RecordWildCards #-}
@@ -938,7 +939,7 @@ renderGhcOptions comp _platform@(Platform _arch os) opts
         , ["-hide-all-packages" | flagBool ghcOptHideAllPackages]
         , ["-Wmissing-home-modules" | flagBool ghcOptWarnMissingHomeModules]
         , ["-no-auto-link-packages" | flagBool ghcOptNoAutoLinkPackages]
-        , packageDbArgs implInfo (interpretPackageDBStack Nothing (ghcOptPackageDBs opts))
+        , packageDbArgsDb (interpretPackageDBStack Nothing (ghcOptPackageDBs opts))
         , concat $
             let space "" = ""
                 space xs = ' ' : xs
@@ -999,27 +1000,9 @@ verbosityOpts verbosity
   | verbosity >= Normal = []
   | otherwise = ["-w", "-v0"]
 
--- | GHC <7.6 uses '-package-conf' instead of '-package-db'.
-packageDbArgsConf :: PackageDBStackCWD -> [String]
-packageDbArgsConf dbstack = case dbstack of
-  (GlobalPackageDB : UserPackageDB : dbs) -> concatMap specific dbs
-  (GlobalPackageDB : dbs) ->
-    ("-no-user-package-conf")
-      : concatMap specific dbs
-  _ -> ierror
-  where
-    specific (SpecificPackageDB db) = ["-package-conf", db]
-    specific _ = ierror
-    ierror =
-      error $
-        "internal error: unexpected package db stack: "
-          ++ show dbstack
-
--- | GHC >= 7.6 uses the '-package-db' flag. See
--- https://gitlab.haskell.org/ghc/ghc/-/issues/5977.
 packageDbArgsDb :: PackageDBStackCWD -> [String]
 -- special cases to make arguments prettier in common scenarios
-packageDbArgsDb dbstack = case dbstack of
+packageDbArgsDb = \case
   (GlobalPackageDB : UserPackageDB : dbs)
     | all isSpecific dbs -> concatMap single dbs
   (GlobalPackageDB : dbs)
@@ -1036,11 +1019,6 @@ packageDbArgsDb dbstack = case dbstack of
     isSpecific (SpecificPackageDB _) = True
     isSpecific _ = False
 
-packageDbArgs :: GhcImplInfo -> PackageDBStackCWD -> [String]
-packageDbArgs implInfo
-  | flagPackageConf implInfo = packageDbArgsConf
-  | otherwise = packageDbArgsDb
-
 -- | Split a list of command-line arguments into RTS arguments and non-RTS
 -- arguments.
 splitRTSArgs :: [String] -> ([String], [String])

cabal-install/src/Distribution/Client/CmdRepl.hs

@@ -522,7 +522,7 @@ targetedRepl
         -- into the multi-out directory.
         replOpts'' <- case targetCtx of
           ProjectContext -> return $ replOpts'{replOptionsFlagOutput = Flag dir}
-          _ -> usingGhciScript compiler projectRoot replOpts'
+          _ -> usingGhciScript projectRoot replOpts'
 
         let buildCtx' = buildCtx & lElaboratedShared . lPkgConfigReplOptions .~ replOpts''
         printPlan verbosity baseCtx'' buildCtx'
@@ -591,7 +591,7 @@ targetedRepl
         -- single target repl
         replOpts'' <- case targetCtx of
           ProjectContext -> return replOpts'
-          _ -> usingGhciScript compiler projectRoot replOpts'
+          _ -> usingGhciScript projectRoot replOpts'
 
         let buildCtx' = buildCtx & lElaboratedShared . lPkgConfigReplOptions .~ replOpts''
         printPlan verbosity baseCtx'' buildCtx'
@@ -761,20 +761,13 @@ generateReplFlags includeTransitive elaboratedPlan OriginalComponentInfo{..} = f
 -- so we need to tell ghci to change back to the correct directory.
 --
 -- The @-ghci-script@ flag is path to the ghci script responsible for changing to the
--- correct directory. Only works on GHC >= 7.6, though. 🙁
-usingGhciScript :: Compiler -> FilePath -> ReplOptions -> IO ReplOptions
-usingGhciScript compiler projectRoot replOpts
-  | compilerCompatVersion GHC compiler >= Just minGhciScriptVersion = do
-      let ghciScriptPath = projectRoot </> "setcwd.ghci"
-      cwd <- getCurrentDirectory
-      writeFile ghciScriptPath (":cd " ++ cwd)
-      return $ replOpts & lReplOptionsFlags %~ (("-ghci-script" ++ ghciScriptPath) :)
-  | otherwise = return replOpts
-
--- | First version of GHC where GHCi supported the flag we need.
--- https://downloads.haskell.org/~ghc/7.6.1/docs/html/users_guide/release-7-6-1.html
-minGhciScriptVersion :: Version
-minGhciScriptVersion = mkVersion [7, 6]
+-- correct directory.
+usingGhciScript :: FilePath -> ReplOptions -> IO ReplOptions
+usingGhciScript projectRoot replOpts = do
+  let ghciScriptPath = projectRoot </> "setcwd.ghci"
+  cwd <- getCurrentDirectory
+  writeFile ghciScriptPath (":cd " ++ cwd)
+  return $ replOpts & lReplOptionsFlags %~ (("-ghci-script" ++ ghciScriptPath) :)
 
 -- | This defines what a 'TargetSelector' means for the @repl@ command.
 -- It selects the 'AvailableTarget's that the 'TargetSelector' refers to,

changelog.d/11710.md

@@ -0,0 +1,8 @@
+---
+synopsis: "Remove legacy support for GHC < 7.6"
+packages: [Cabal, cabal-install]
+prs: 11710
+---
+Removed compatibility logic for GHC versions prior to 7.6. This simplifies
+package database stack handling and unifies the flag generation logic in
+`Distribution.Simple.GHC` and `Distribution.Simple.Program.GHC`.