Simon Marlow schrieb:

Before we add support for this to Cabal, we should ask why it is needed. The only reason (that I know of) to hide a package by default is because its namespace conflicts with another exposed package. Is that the case here?

Yes, I had identical hierarchical module names in two packages, one was a HaXml-13-CVS Cabal package, the other an old uni-haxml package that's usually included via ghc's -package-conf option into our sources. Unfortunately both versions have been modified in different directions (and almost nobody wants to touch our old uni code). Nevertheless, I thought, it should be possible to install different hidden versions of libraries such that users (or user groups) are free to explicitly pick the version that suits them most (although they'll have to stick to that single version then). Cheers Christian