Add `cabal-doctest`

[sol]

Initial implementation: #425
Based on: https://github.com/mpickering/cabal-doctest-demo/blob/master/cabal-doctest

Related discussions:

• Doctest ghc pkg fix haskell/cabal#10057
• Add cabal-doctest exe as cabal external command #424

TODO:

• cabal-doctest: Cache doctest executables #437
• cabal-doctest: Add support for --with-compiler #439
• Get rid of the cabal build step by capturing the REPL arguments with --repl-multi-file. This possibly also needs --keep-temp-files. Then call doctest with --no-magic. cabal-doctest: Get rid of separate cabal build step #441
• accept component, eg cabal doctest spec cabal-doctest: Accept component #442
• Accept --ignore-project
• Accept --list-options
• Accept --help
• Accept --dry-run
• Directly accept doctest options like --verbose or --fast
• Allow to disable QuickCheck to avoid dependency cycles. Fix doctests haskell/random#165

[hsyl20]

Thanks for your work on this!

I've just noticed that there is an issue when multi-repl: True is present in a cabal.project. The repl loads the target but doesn't run the tests:

Example from https://github.com/haskus/packages/actions/runs/10195092999/job/28203068431:

Run cabal doctest
Resolving dependencies...
Build profile: -w ghc-9.8.2 -O1
In order, the following will be built (use -v for more details):
 - doctest-0.22.9 (lib) (requires build)
 - doctest-0.22.9 (exe:doctest) (requires build)
Starting     doctest-0.22.9 (lib)
Building     doctest-0.22.9 (lib)
Installing   doctest-0.22.9 (lib)
Completed    doctest-0.22.9 (lib)
Starting     doctest-0.22.9 (exe:doctest)
Building     doctest-0.22.9 (exe:doctest)
Installing   doctest-0.22.9 (exe:doctest)
Completed    doctest-0.22.9 (exe:doctest)
Copying 'doctest' to
'/home/runner/.cabal/doctest/ghc-9.8.2-6fbce3708d1cdaa02b114e8244ac58f9/doctest-0.22.9'
doctest version 0.22.9
using version 9.8.2 of the GHC API
using /usr/local/.ghcup/ghc/9.8.2/bin/ghc-9.8.2
Resolving dependencies...
Build profile: -w ghc-9.8.2 -O1
In order, the following will be built (use -v for more details):
 - haskus-utils-data-1.4 (interactive) (lib) (configuration changed)
 - haskus-utils-data-1.4 (interactive) (test:tests) (configuration changed)
Configuring library for haskus-utils-data-1.4...
Configuring test suite 'tests' for haskus-utils-data-1.4...
Preprocessing test suite 'tests' for haskus-utils-data-1.4...
Preprocessing library for haskus-utils-data-1.4...
GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/runner/.cabal/doctest/ghc-9.8.2-6fbce3708d1cdaa02b114e8244ac58f9/init-ghci-0.22.9
[ 1 of 12] Compiling Haskus.Utils.Either[haskus-utils-data-1.4-inplace]
[ 2 of 12] Compiling Haskus.Utils.Functor[haskus-utils-data-1.4-inplace]
[ 3 of 12] Compiling Haskus.Utils.InfList[haskus-utils-data-1.4-inplace]
[ 4 of 12] Compiling Haskus.Utils.List[haskus-utils-data-1.4-inplace]
[ 5 of 12] Compiling Haskus.Utils.Map[haskus-utils-data-1.4-inplace]
[ 6 of 12] Compiling Haskus.Utils.Map.Strict[haskus-utils-data-1.4-inplace]
[ 7 of 12] Compiling Haskus.Utils.Maybe[haskus-utils-data-1.4-inplace]
[ 8 of 12] Compiling Haskus.Utils.Monad[haskus-utils-data-1.4-inplace]
[ 9 of 12] Compiling Haskus.Utils.Tuple[haskus-utils-data-1.4-inplace]
[10 of 12] Compiling Haskus.Utils.HList[haskus-utils-data-1.4-inplace]
[11 of 12] Compiling Main[haskus-utils-data-1.4-inplace-tests]
Ok, 11 modules loaded.
ghci> Leaving GHCi.
Examples: 0  Tried: 0  Errors: 0  Failures: 0

Similarly, when I try cabal doctest all it requires multi-repl: True but if enabled it just drops me into a repl with all the modules loaded.

[sol]

@hsyl20 does passing --disable-multi-repl to cabal doctest on the command line work as a workaround?

[hsyl20]

@sol Yes it does