I believe there is a post on this from the Yesod developers:
http://www.yesodweb.com/blog/2012/04/cabal-meta
It looks like the suggest using a better wrapper around cabal and making
virtual play-spaces to install into. I confess, I haven't taken the time to
learn it, but it sounds like they have thought through this a couple times.
Good luck!
Tim
On Thu, Apr 26, 2012 at 9:42 AM, Lorenzo Bolla
Hi all,
I've recently installed the latest yesod-platform with cabal and now I'd like to install yesod-markdown, too.
Problem is, yesod-markdown refuses to install because it depends on libraries older than the ones installed by yesod-platform on my system: for example, yesod-markdown requires 0.4 <= blaze-html < 0.5, but latest yesod-platform depends on blaze-html 0.5.0.
This problem is obviously more general, and so is my question: How to handle packages that depend of different versions of the same library?
Would you just install the "highest common version" across all the packages that depend on it? What if it doesn't exist? Would you manually patch the cabal files for all the packages in the dependency tree, hoping that newest libraries are backward compatible? Would you wait for the library developers to update their cabal file every time a library they rely upon changes?
To me, it looks like dependencies in .cabal files are usually too strict. Or, packages should agree on the meaning of "minor" version numbers. For example, if blaze-html's API did not change from 0.4 to 0.5 (supposing that API changes are identified by a change in the major version number), then there is no point in the libraries that depend on it to require a dependency <0.5. Is this rule of minor/major version numbers followed/agreed upon in Haskell libraries?
Thanks, L.
-- Lorenzo Bolla http://lbolla.info
_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners