Hi Matthijs,
I've installed the vimball, and it spit a few errors at me. In particular, it couldn't find the haddock documentation directory. A quick look at haskell_doc.vim shows that it should autodetect the directory. However, for some reason my ghc-pkg command returns the doc directory twice:
$ ghc-pkg field base haddock-html haddock-html: /usr/local/ghc-6.10.1/share/doc/ghc/libraries/base haddock-html: /usr/local/ghc-6.10.1/share/doc/ghc/libraries/base
Interesting. The reason for the double listing is that recent GHCs come with two base packages (since the packages differ in content, having both point to the same documentation location looks wrong to me, btw).
The haskell_doc.vim contains the following line, which seems to deal with multiple lines:
let field = substitute(system(g:ghc_pkg . ' field base haddock-html'),'\n','','')
This just used to remove the final '\n', in the days when multiple versions of base were still unthinkable. What I'm really after in that part of the script is the location of the GHC docs, and the library index (the actual package docs are processed later). Unfortunately, past GHC versions haven't been too helpful (#1226, #1878, #1572), hence all that guesswork in my scripts (for a while, there was a ghc --print-docdir, but that didn't quite work and disappeared quickly, nowadays, there is the nice ghc-paths package, but that doesn't give a concrete path for docdir, so I still need to find the http top dir for GHC). I hadn't noticed this change, because (a) the scripts look in "likely suspects" for the docs location as well, and (b) the docs location can be configured (bypassing all that guesswork) by setting 'g:haddock_docdir' before loading the scripts (:help g:haddock_docdir, :help haskellmode-settings-fine). Using g:haddock_docdir to configure the right path for your installation is probably the least wrong thing to do for now, and requires no changes to the scripts, but I'll have a look at how to improve the guesswork code for convenience, looking at the first match only or looking for the relevant directories in all matches.. Thanks for the report! Claus