Consider supporting local documentation with links to Hackage

[harpocrates]

This SO question has got me thinking: what would it take to have local documentation link to Hackage documentation? This might make it possible to follow hyperlinks through transitive dependencies, but without needing to locally build the docs for those dependencies.

So, what would it take? I think:

• Hackage would have to expose the haddock interface files produced by docbuilder
• Cabal should get an option to download the haddock interface files and feed them properly to Haddock (perhaps downloading + handing to Haddock only if no local alternative was found)
• Haddock needs a way of dealing with interface files that aren't local

Perhaps this isn't worth doing at all, but opening an issue just to see what people think about the idea. 😄

[mpilgrem]

Is having local documentation link to Hackage documentation something other than what is currently provided by the standalone-haddock application? If not, I did wonder why standalone-haddock was not an option offered by haddock itself.