Please help beta test "no-reinstall Cabal" (was: Cabal and simultaneous installations of the same package)

Herbert Valerio Riedel hvr at
Sat Aug 29 06:56:53 UTC 2015

Good news, everyone! may be interested to know this has finally come to fruition (just
in time for HIW):


On 2015-03-23 at 09:45:48 +0100, Simon Peyton Jones wrote:
> Dear Cabal developers
> You'll probably have seen the thread about the Haskell Platform.
> Among other things, this point arose:
> |  Another thing we should fix is the (now false) impression that HP gets in
> |  the way of installing other packages and versions due to cabal hell.
> People mean different things by "cabal hell", but the inability to 
> 	simultaneously install multiple versions of the same package,
> 	compiled against different dependencies
> is certainly one of them, and I think it is the one that Yitzchak is referring to here.
> But some time now GHC has allowed multiple versions of the same
> package (compiled against different dependencies) to be installed
> simultaneously.  So all we need to do is to fix Cabal to allow it too,
> and thereby kill of a huge class of cabal-hell problems at one blow.
> But time has passed and it hasn't happened. Is this because I'm misunderstanding?  Or because it is harder than I think?  Or because there are much bigger problems?  Or because there is insufficient effort available?  Or what?
> Unless I'm way off beam, this "multiple installations of the same package" thing has been a huge pain forever, and the solution is within our grasp.  What's stopping us grasping it?

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