Allow internal modules to be tested

[martijnbastiaan]

As mentioned in the migration guide, doctest-parallel can only test exported binders:

---

---

It would be nice if modules could be marked to run in "interpreted mode", i.e.:

  {-# ANN module "doctest-parallel: --interpret" #-}

By copying these internal modules to a temporary directory and using GHCi to interpret them, we could get the best of both worlds: run as many examples as possible against compiled/optimized code, while also being able to run doctests on internal ones. (We don't necessarily have to copy them, but I'm unsure how thread-safe starting multiple GHCi sessions is..)

[tmplt]

Do I understand correctly that a feature like this is required to test non-exported functions, too? E.g.

module SomeHidden (funA) where

funA = funB

-- | Test non-exported function
-- >>> funB
-- True
funB = True

[martijnbastiaan]

Yes, that's correct. In your example, only funA is accessible when loading compiled code.