Haddocks of multiple components

Haddock supports building documentation of multiple components. First, one needs to build haddocks of all components which can be done with:

cabal haddock --haddock-html \
              --haddock-quickjump \
              --haddock-option="--use-index=../doc-index.html" \
              --haddock-option="--use-contents=../index.html" \
              --haddock-option="--base-url=.." \

The new --base-url option will allow to access the static files from the main directory (in this example its the relative ./.. directory). It will also prevent haddock from copying its static files to each of the documentation folders, we’re only need a single copy of them where the --base-url option points to.

The second step requires to copy all the haddocks to a common directory, let’s say ./docs, this will depend on your project and it might look like:

cp -r dist-newstyle/build/x86_64-linux/ghc-9.0.1/package-a- docs
cp -r dist-newstyle/build/x86_64-linux/ghc-9.0.1/package-b- docs

Note that you can also include documentation of other packages in this way, e.g. base, but you need to know where it is hidden on your hard-drive.

To build html and js (quickjump) indexes one can now invoke haddock with:

haddock \
  -o docs \
  --quickjump --gen-index --gen-contents \
  --read-interface=package-a,docs/package-a/package-a.haddock \

Note: the PATH in --read-interface=PATH,... must be a relative url of a package it points to (relative to the docs directory).

There’s an example project which shows how to do that posted here, which haddocks are served on github-pages.