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

[Erik Hesselink]

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.

Erik
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