On Wed, Aug 15, 2012 at 9:19 PM, Ivan Lazar Miljenovic <ivan.miljeno...@gmail.com> wrote: > On 16 August 2012 08:55, Brandon Allbery <allber...@gmail.com> wrote: >> Indeed. But the ghc release that split up base broke cabalised packages >> with no warning to users until they failed to compile. Upper bounds were >> put in place to avoid that kind of breakage in the future. > > I like having upper bounds on version numbers... right up until people > abuse them.
I also tend to favor having upper bounds. Obviously they impose a cost, but it's not clear to me at all that getting rid of them is a better tradeoff. I've had projects that I put aside for awhile only to come back and discover that they would no longer build because I hadn't put upper bounds on all my package dependencies. With no upper bounds, a package might not be very likely to break for incremental version bumps, but eventually it *will* break. And when it does it's a huge pain to get it building again. If I have put effort into making a specific version of my package work properly today, I want it to always work properly in the future (assuming that everyone obeys the PVP). I don't think it's unreasonable that some activation energy be required to allow one's project to work with a new version of some upstream dependency. Is that activation energy too high right now? Almost definitely. But that's a tool problem, not a problem with the existence of upper bounds themselves. One tool-based way to help with this problem would be to add a flag to Cabal/cabal-install that would cause it to ignore upper bounds. (Frankly, I think it would also be great if Cabal/cabal-install enforced upper version bounds automatically if none were specified.) Another approach that has been discussed is detecting dependencies that are only used internally[1], and I'm sure there are many other possibilities. In short, I think we should be moving more towards purely functional builds that reduce the chance that external factors will break things, and it seems like removing upper version bounds is a step in the other direction. [1] http://cdsmith.wordpress.com/2011/01/21/a-recap-about-cabal-and-haskell-libraries/ _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
