doctests: switch to the preffered method of calling the tool

[ulysses4ever]

which is cabal repl --with-ghc=doctest. This not only catches up with the current upstream recommendations, but also simplifies the usage: before this change calling doctest required you to set up an environment with QuickCheck available (we used to do it via cabal-env). The new method takes care of it automatically.

Also add some docs to fix #8147

---

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[ulysses4ever]

I really wish fix-whitespace showed me the exact problem, not only the filename. As for the other failure, I think I know how to fix it.

[ulysses4ever]

Oh Lord, it's failing even locally now. I can swear to god that yesterday it worked just fine...

[andreasabel]

I really wish fix-whitespace showed me the exact problem, not only the filename. As for the other failure, I think I know how to fix it.

You can run fix-whitespace locally and it will fix the whitespace problems.
But others have complained before:

• Enhancement: more verbose error reporting agda/fix-whitespace#7

[ulysses4ever]

@andreasabel that's what I ended up doing, yes. The issue is: I need to have it locally to do that, and that's not always convenient (I have many environments...). I much rather I saw the issue in the CI and could fix it manually instead of installing it, if it seems easier to me.

[ulysses4ever]

All right, fellas. The new method seems to be more sensitive to GHC version. Seems to work fine now.

[andreasabel]

Great work!

Maybe the local workflow (Makefile) could be made more robust by having and executing goals for installing doctest for the current GHC version, and checking for correct doctest versions. Some ideas in:

• A makefile to run doctests in Cabal-syntax #8703

[Mikolaj]

Thanks a lot!

[ulysses4ever]

@andreasabel could you please take another look and comment further or approve?

[andreasabel]

Thanks for this great work of research and implementation!
(I know what it takes, as I have spent many days just to get doctest working on various projects.)

[ulysses4ever]

Thanks @andreasabel! I just stood on the shoulders of giants (nomeata and wismill, in this case). By the way, if you have a spare winter evening, I'm sure you'll enjoy this recent Haskell Discourse thread about various ways of doctesting. (Most of it you probably know by now, though)

[Mikolaj]

@mergify backport 3.10

[mergify]

backport 3.10

✅ Backports have been created

• #8804 doctests: switch to the preffered method of calling the tool (backport #8735) has been created for branch 3.10