Doctest running via doctest-parallel

`doctest-parallel` (13sec) is faster than plain `doctest` (30sec).
By default, `doctest-parallel` only runs the tests for exported
functions, but this can be worked around if necessary (see docs).

Author: andreasabel

hackage-server.cabal

@@ -564,3 +564,12 @@ test-suite HashTests
     , tasty       ^>= 1.4
     , tasty-hunit ^>= 0.10
 
+test-suite DocTests
+  import:         test-defaults
+
+  type:           exitcode-stdio-1.0
+  main-is:        DocTestMain.hs
+
+  build-depends:
+    , lib-server
+    , doctest-parallel ^>= 0.2.1

tests/DocTestMain.hs

@@ -0,0 +1,27 @@
+-- | `doctest-parallel` runner for `hackage-server` library.
+module Main where
+
+import Data.List
+         ( isPrefixOf )
+import System.Environment
+         ( getArgs )
+
+import Distribution.ModuleName
+         ( components )
+
+import Test.DocTest
+         ( mainFromLibrary )
+import Test.DocTest.Helpers
+         ( Library(..), extractSpecificCabalLibrary, findCabalPackage )
+
+-- | Doctest @hackage-server:lib-server@.
+main :: IO ()
+main = do
+  args <- getArgs
+  pkg  <- findCabalPackage "hackage-server"
+  -- Need to give the library name, otherwise the parser does not find it.
+  lib  <- extractSpecificCabalLibrary (Just "lib-server") pkg
+  -- Need to filter out the @Paths_*@ modules, as they are not found by doctest-parallel.
+  let f    = not . ("Paths_" `isPrefixOf`) . head . components
+  let lib' = lib{ libModules = filter f $ libModules lib }
+  mainFromLibrary lib' args