cabal-doctest: Get rid of separate cabal build step

.github/workflows/cabal-doctest.yml

@@ -35,6 +35,7 @@ jobs:
       - run: cabal path -v0 --installdir >> $GITHUB_PATH
         if: matrix.os == 'macos-12'
 
+      - run: ghcup install ghc 9.6 --no-set
       - run: ghcup install ghc 8.6.5 --no-set
 
       - run: cabal --version
@@ -43,6 +44,7 @@ jobs:
       - run: cabal install -f cabal-doctest
       - run: cabal doctest
 
+      - run: cabal doctest -w ghc-9.6
       - run: cabal doctest -w ghc-8.6.5
 
   cabal-doctest-success:

package.yaml

@@ -65,6 +65,7 @@ library:
     ghc-paths: ">= 0.1.0.9"
     transformers:
     containers:
+    temporary:
 
 flags:
   cabal-doctest:

src/Cabal.hs

@@ -3,12 +3,15 @@ module Cabal (externalCommand) where
 
 import           Imports
 
+import           Data.List
+import           Data.Version (makeVersion)
 import           System.IO
+import           System.IO.Temp
 import           System.Environment
-import           System.Exit (exitWith)
+import           System.Exit
 import           System.Directory
 import           System.FilePath
-import           System.Process
+import           System.Process hiding (system)
 
 import qualified Info
 import           Cabal.Paths
@@ -40,7 +43,6 @@ run cabal args = do
       , "--program-suffix", "-" <> Info.version
       , "--install-method=copy"
       , "--with-compiler", ghc
-      , "--with-hc-pkg", ghcPkg
       ]
 
   doesFileExist script >>= \ case
@@ -49,16 +51,29 @@ run cabal args = do
 
   callProcess doctest ["--version"]
 
-  callProcess cabal ("build" : "--only-dependencies" : discardReplOptions args)
+  let
+    repl extraArgs = system cabal ("repl"
+      : "--build-depends=QuickCheck"
+      : "--build-depends=template-haskell"
+      : ("--repl-options=-ghci-script=" <> script)
+      : args ++ extraArgs)
+
+  case ghcVersion < makeVersion [9,4] of
+    True -> do
+      callProcess cabal ("build" : "--only-dependencies" : discardReplOptions args)
+      repl ["--with-compiler", doctest, "--with-hc-pkg", ghcPkg]
+
+    False -> do
+      withSystemTempDirectory "cabal-doctest" $ \ dir -> do
+        repl ["--keep-temp-files", "--repl-multi-file", dir]
+        files <- filter (isSuffixOf "-inplace") <$> listDirectory dir
+        options <- concat <$> mapM (fmap lines . readFile . combine dir) files
+        system doctest ("--no-magic" : options)
 
-  rawSystem cabal ("repl"
-    : "--build-depends=QuickCheck"
-    : "--build-depends=template-haskell"
-    : ("--repl-options=-ghci-script=" <> script)
-    : args ++ [
-      "--with-compiler", doctest
-    , "--with-hc-pkg", ghcPkg
-    ]) >>= exitWith
+system :: FilePath -> [FilePath] -> IO ()
+system name args = rawSystem name args >>= \ case
+  ExitSuccess -> pass
+  err -> exitWith err
 
 writeFileAtomically :: FilePath -> String -> IO ()
 writeFileAtomically name contents = do

src/Cabal/Paths.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE StrictData #-}
 module Cabal.Paths (
   Paths(..)
 , paths
@@ -19,7 +20,8 @@ import           System.Process
 import           Text.ParserCombinators.ReadP
 
 data Paths = Paths {
-  ghc  :: FilePath
+  ghcVersion :: Version
+, ghc  :: FilePath
 , ghcPkg :: FilePath
 , cache :: FilePath
 } deriving (Eq, Show)
@@ -45,11 +47,15 @@ paths cabal args = do
 
   ghc <- getPath "'ghc'" "compiler-path"
 
-  ghcVersion <- strip <$> readProcess ghc ["--numeric-version"] ""
+  ghcVersionString <- strip <$> readProcess ghc ["--numeric-version"] ""
+
+  ghcVersion <- case parseVersion ghcVersionString of
+    Nothing -> die $ "Cannot determine GHC version from '" <> ghcVersionString <> "'."
+    Just version -> return version
 
   let
     ghcPkg :: FilePath
-    ghcPkg = takeDirectory ghc </> "ghc-pkg-" <> ghcVersion
+    ghcPkg = takeDirectory ghc </> "ghc-pkg-" <> ghcVersionString
 #ifdef mingw32_HOST_OS
       <.> "exe"
 #endif
@@ -61,12 +67,13 @@ paths cabal args = do
   abi <- strip <$> readProcess ghcPkg ["--no-user-package-db", "field", "base", "abi", "--simple-output"] ""
 
   cache_home <- getPath "Cabal's cache directory" "cache-home"
-  let cache = cache_home </> "doctest" </> "ghc-" <> ghcVersion <> "-" <> abi
+  let cache = cache_home </> "doctest" </> "ghc-" <> ghcVersionString <> "-" <> abi
 
   createDirectoryIfMissing True cache
 
   return Paths {
-    ghc
+    ghcVersion
+  , ghc
   , ghcPkg
   , cache
   }