[Haskell-cafe] Is it just me... or is cabal/hackage a little broken?

Brandon S. Allbery KF8NH allbery at ece.cmu.edu
Tue Dec 22 20:42:32 EST 2009

On Dec 22, 2009, at 18:14 , Bardur Arantsson wrote:
>  Warning: This package indirectly depends on multiple versions of the
>  same package. This is highly likely to cause a compile failure.
> The thing is, I got the same message while trying to compile locally  
> and it turned out that all I had to do was to
>   $ cabal install <PKG-X>
> on all the packages that cabal complained about. So why doesn't  
> hackage do this automagically when I upload a package? How am I  
> supposed to know which versions of my package's dependencies (or  
> their dependencies) are the most recently compiled by hackage?

You got lucky; your case can be solved that way.  In the general case,  
you can have packages that work only with certain versions of other  
packages, and you can potentially end up with nasty unsolvable  
dependency loops as a result.  (Look for "diamond dependency problem"  
on Google if you want the ugly details.)

brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH

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