`Distribution.Extra.Doctest` is deprecated and makes installing with nix more difficult

[tysonzero]

Deprecation indicator

When installing with nix:

setupCompileFlags: -package-db=/build/setup-package.conf.d -j4 +RTS -A64M -RTS -threaded -rtsopts
[1 of 1] Compiling Main             ( Setup.hs, /build/Main.o )

Setup.hs:3:1: error:
    Could not find module ‘Distribution.Extra.Doctest’
    Perhaps you meant Distribution.Simple.Doctest (from Cabal-3.2.1.0)
    Use -v (or `:set -v` in ghci) to see a list of the files searched for.
  |
3 | import Distribution.Extra.Doctest (defaultMainWithDoctests)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[tysonzero]

Looks like the build issue only occurs when building with ghcjs.

[kim]

Seems like this is the successor: https://github.com/phadej/cabal-extras/tree/master/cabal-docspec

[tysonzero]

Potentially? Although the GPL license seems like it could be a problem.

[kim]

The interpretation seems to be that a library which uses it to drive its doctest suite is not a derived work. As evidenced by lens (BSD2) using cabal-docspec, which @phadej himself proposed.

[tysonzero]

Ah perfect! It seems like cabal-docspec doesn't require a custom-setup stanza, so perhaps this will fix the nix/ghcjs issue.

My attempts to use CPP to workaround the issue have been unsuccessful. It appears that __GHCJS__ and ghcjs_HOST_OS are not set when compiling Setup.hs.

[kim]

Would you be able to try it out (and maybe submit a patch)? Afaiu, the issue is with nix specifically, and I have no way to test.

[tysonzero]

To be honest I have never used any of the doctest variants.

I've tried to install cabal-docspec from source via various cabal commands but they all give different error messages. Are there proper install and usage instructions anywhere?

In terms of fixing GHCJS I'm fairly sure that anything not using a custom-setup clause should work just fine.

[kim]

It builds fine over here, but it seems like a `cabal-docspec` _executable_ is then required for building. Perhaps we should just move the property tests to a normal test suite? I also notice that the `git-remote-ipfs` package is broken irrecoverably, because `git` was not updated past MonadFail.

[tysonzero]

A normal test suite sounds reasonable to me.

Hmm yeah git may need some PR's or a fork.