cabal does not build documentation for repl

[oivulf]

cabal (3.4.0) does not build documentation for ghci, even when
cabal build --enable-documentation

To Reproduce
cabal v2-build --enable-documentation
cabal v2-repl
Prelude Test.Util> import qualified Data.Vector as V
Prelude V Test.Util> :doc V.partition
ghc: Can't find any documentation for Data.Vector.
This is probably because the module was compiled without '-haddock',
but it's also possible that the module contains no documentation.

Expected behavior
obtain documentation, this used to work in previous versions?

System information
Build profile: -w ghc-8.8.4 -O1
linux debian
ghc, cabal from ghcup

[fgaz]

All v2 commands except for configure are stateless, so you should either do cabal v2-repl --enable-documentation, or you can first do cabal v2-configure --enable-documentation, then cabal v2-repl

[oivulf]

I tried cabal v2-repl --enable-documentation,
but the effect is the same, no documentation in the repl

[sjakobi]

I can reproduce this or a similar issue like this:

$ cabal repl -b vector --enable-documentation
Resolving dependencies...
Build profile: -w ghc-9.0.1 -O1
In order, the following will be built (use -v for more details):
 - primitive-0.7.1.0 (lib) (requires build)
 - vector-0.12.2.0 (lib) (requires build)
 - fake-package-0 (lib) (first run)
Starting     primitive-0.7.1.0 (lib)
Building     primitive-0.7.1.0 (lib)
Haddock      primitive-0.7.1.0 (lib)
Installing   primitive-0.7.1.0 (lib)
Completed    primitive-0.7.1.0 (lib)
Starting     vector-0.12.2.0 (lib)
Building     vector-0.12.2.0 (lib)
Haddock      vector-0.12.2.0 (lib)
Installing   vector-0.12.2.0 (lib)
Completed    vector-0.12.2.0 (lib)
Configuring library for fake-package-0..
Preprocessing library for fake-package-0..
Warning: No exposed modules
GHCi, version 9.0.1: https://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /tmp/cabal-repl.-59300/setcwd.ghci
ghci>  import qualified Data.Vector as V
ghci> :doc V.partition
ghc: Can't find any documentation for Data.Vector.
This is probably because the module was compiled without '-haddock',
but it's also possible that the module contains no documentation.

Try re-compiling with '-haddock'.

It's weird that the documentation can't be found, because it was apparently built.

[dmwit]

Thought I'd quickly mention a workaround for this. For packages that you are currently developing, you can request docs at repl time:

cabal repl --ghc-options -haddock
*Test> :doc test
 Hello, world!

If you want docs available for dependencies, too, then as far as I can tell you must use a cabal.project (or .local), but it is still possible:

package *
    ghc-options: -haddock

This is a full rebuild, so beware of adding or removing this chunk if you've already got the project built!