Add cabal-doctest

.gitattributes

@@ -1,2 +1 @@
-/doctest.cabal linguist-generated=true
-/ghci-wrapper/ghci-wrapper.cabal linguist-generated=true
+doctest.cabal linguist-generated=true

driver/cabal-doctest.hs

@@ -0,0 +1,36 @@
+{-# LANGUAGE LambdaCase #-}
+module Main (main) where
+
+import           Prelude
+
+import           Data.Version
+import           System.Environment
+import           System.Exit
+import           System.FilePath
+import           System.IO.Temp (withSystemTempDirectory)
+import           System.Process
+
+import           Paths_doctest (version)
+
+main :: IO ()
+main = do
+  args <- getArgs
+  lookupEnv "CABAL" >>= \ case
+    Nothing -> run "cabal" args
+    Just cabal -> run cabal (drop 1 args)
+
+run :: String -> [String] -> IO ()
+run cabal args = withSystemTempDirectory "doctest" $ \ dir -> do
+  let
+    doctest = dir </> "doctest"
+    script = dir </> "init-ghci"
+  callProcess cabal ["install", "--ignore-project", "--installdir=" <> dir, "--install-method=symlink", "doctest-" <> showVersion version]
+  callProcess (dir </> "doctest") ["--version"]
+  callProcess cabal ("build" : "--only-dependencies" : args)
+  writeFile script ":seti -w -Wdefault"
+  spawnProcess cabal ("repl"
+    : "--build-depends=QuickCheck"
+    : "--build-depends=template-haskell"
+    : "--repl-options=-ghci-script=" <> script
+    : "--with-ghc" : doctest
+    : args) >>= waitForProcess >>= exitWith

package.yaml

@@ -59,11 +59,19 @@ library:
   - Test.DocTest.Internal.Parse
   - Test.DocTest.Internal.Run
 
-executable:
-  main: Main.hs
-  ghc-options: -threaded
-  source-dirs: driver
-  dependencies: doctest
+executables:
+  doctest:
+    main: Main.hs
+    ghc-options: -threaded
+    source-dirs: driver
+    dependencies: doctest
+
+  cabal-doctest:
+    main: cabal-doctest.hs
+    ghc-options: -threaded
+    source-dirs: driver
+    dependencies:
+    - temporary
 
 tests:
   spec: