Hspec: discovery, custom main, and passing argument to spec - haskell

Question

I am trying to use hspec-discover along with custom Main. Custom Main is a bracket that creates a file descriptor to be used by all Spec's.
This is my Spec.hs:
{-# OPTIONS_GHC -F -pgmF hspec-discover -optF --module-name=Spec #-}
This is my Main.hs:
module Main (main) where
import Control.Exception
import System.Posix.IO
import System.Posix.Files
import Test.Hspec
import Spec (spec)
main :: IO ()
main = bracket
(openFd verybigFile ReadWrite (Just 384) defaultFileFlags)
(\fd -> closeFd fd >> removeLink verybigFile)
(\fd -> hspec (spec fd))
where
verybigFile = "test/verybigFile"
For my spec in individual autodiscovered module to accept the file descriptor argument, I need to declare it as
spec :: Fd -> Spec
but hspec-discover demands that spec is declared as
spec :: Spec
otherwise autogenerated module does not compile:
test/Spec.hs:8:68:
Couldn't match type `System.Posix.Types.Fd -> Spec'
with `hspec-core-2.1.7:Test.Hspec.Core.Spec.Monad.SpecM () ()'
Expected type: hspec-core-2.1.7:Test.Hspec.Core.Spec.Monad.SpecWith
()
Actual type: System.Posix.Types.Fd -> Spec
In the second argument of `describe', namely `SendfileSpec.spec'
In the second argument of `postProcessSpec', namely
`(describe "Sendfile" SendfileSpec.spec)'
In the expression:
postProcessSpec
"test/SendfileSpec.hs" (describe "Sendfile" SendfileSpec.spec)
So, how to pass an argument to the spec without disturbing autodiscovery? My imagination drifts towards IORef's but the idea makes me shudder. What would be a Right Way to do it?

Answer 1

Sharing values across spec files is currently not support with hspec-discover. But you can still share values within the same spec file. The following works:
FooSpec.hs:
module FooSpec (spec) where
import Test.Hspec
import System.IO
spec :: Spec
spec = beforeAll (openFile "foo.txt" ReadMode) $ afterAll hClose $ do
describe "hGetLine" $ do
it "reads a line" $ \h -> do
hGetLine h `shouldReturn` "foo"
it "reads an other line" $ \h -> do
hGetLine h `shouldReturn` "bar"
Spec.hs:
{-# OPTIONS_GHC -F -pgmF hspec-discover #-}
But note that beforeAll is generally considered a code smell. It's good practice to use before instead if possible.