[Haskell-cafe] How to determine correct dependency versions for a library?

Alexander Kjeldaas alexander.kjeldaas at gmail.com
Wed Nov 14 14:42:55 CET 2012

On 14 November 2012 07:51, Erik Hesselink <hesselink at gmail.com> wrote:

> On Wed, Nov 14, 2012 at 10:57 AM, Roman Cheplyaka <roma at ro-che.info>wrote:
>> * Ivan Lazar Miljenovic <ivan.miljenovic at gmail.com> [2012-11-14
>> 20:53:23+1100]
>> > Doesn't this prevent the error of "this package won't build" (even if
>> > the error message doesn't precisely say that)?
>> Yeah, it replaces one error with another. How is it supposed to help me
>> if I really want to build this package? Instead of fixing just the code,
>> I now have to fix the cabal file as well!
> The error might be clearer, since it comes up right away, and points you
> to the right package, together with the reason (doesn't support the right
> base version).
> If it started to build instead, it might fail in the middle, with some
> error that you might not know is caused by changes in base.
> But the question comes down to numbers: how often do packages break with
> new base versions, how soon do people need to be able to use the new GHC
> without changing other packages, etc. Some might argue that packages
> 'usually' work, so we should leave out upper bounds, even if it gives worse
> errors. Others say the errors are so bad, or badly timed, that we should
> have upper bounds, and the work for maintainers, while greater, is not too
> large. I know what I think, but nobody has concrete numbers about breakages
> with new base versions, amount of time spent updating packages, unupdated
> packages etc. Some can be found with a grep over the hackage tarball, but
> most can't.
This particular problem has a better solution - try building, and if it
fails, print out the original cabal error after the compiler error.


> Erik
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