Is it just me... or is cabal/hackage a little broken?
Hi all, Sorry about the inflammatory title, but I just got this message from an uploaded package ("hums"): 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? For the record: I did do a "Check package" upload first. It didn't complain. Is this an intractable problem? Am I being overly demanding (probably)? Cheers, Bárður
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@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH
On Wed, 2009-12-23 at 00:14 +0100, Bardur Arantsson wrote:
Hi all,
Sorry about the inflammatory title, but I just got this message from an uploaded package ("hums"):
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.
Right. I wrote a simple constraint solver for cabal-install to solve this problem (the diamond dependency problem).
So why doesn't hackage do this automagically when I upload a package?
The single hackage buildbot does not do anything smart. It does not use the cabal-install solver, so it regularly runs into the diamond dep problem.
How am I supposed to know which versions of my package's dependencies (or their dependencies) are the most recently compiled by hackage?
You're not. My suggestion is don't worry about it not building on hackage. The quality of the build results there just are not that good. For the new hackage server we're using a different design that will generate good build results.
For the record: I did do a "Check package" upload first. It didn't complain.
Right. It's not a problem with the package itself.
Is this an intractable problem? Am I being overly demanding (probably)?
No, not intractable. The cabal-install solver can handle it most of the time. Duncan
participants (3)
-
Bardur Arantsson -
Brandon S. Allbery KF8NH -
Duncan Coutts