bug report: Cabal hides library

[Duncan Coutts]

On Wed, 2006-09-20 at 15:51 +0400, Bulat Ziganshin wrote:
> Hello libr,
> 
> i think it's appropriate place to complain about Cabal?

Sure. (Or the cabal bug tracker or the cabal-devel list)

> situation: ghc 6.4.2 (2006.06.09) with built-in Cabal. i install
> package with the following dependencies:
> 
> Build-Depends:      base, ArrayRef==0.1, fps>=0.7, template-haskell
> 
> there are ArrayRef 0.1 (hidden) and ArrayRef 0.1.1 (exposed) installed
> 
> Cabal correctly selects ArrayRef 0.1 when building the lib. but on
> installation it makes the following trick:
> 
> Registering Streams-0.2.2...
> Reading package info from ".installed-pkg-config" ... done.
> Warning: hiding the following packages to avoid conflict:
>   ArrayRef-0.1.1 Streams-0.1.6
> 
> hiding old version of Stream library is correct, but why the hell it hides
> old ArrayRef library??? as the final result, both old and new ArrayRef
> libraries are hidden:

It is ghc-pkg that does this hiding upon registration, not Cabal. Try it
manually, you'll get the same behaviour.

The reason is as ghc-pkg explains: that there would be duplicate modules
exposed otherwise if Streams-0.2.2 and ArrayRef-0.1.1 were exposed at
once. This is because Streams-0.2.2 is exposed and depends on
arrayRef-0.1.

With the recent relaxation in GHC's package/module name space system
ghc-pkg might be able to do something different in this case. Try asking
about it on the ghc-users list.

Duncan