PVP proposal: no upper bounds on non-upgradeable packages

[Edward Kmett]

For this particular issue, in general I'm +1.

The main quibble I have with it the base bound was needed for the 'default
to base 3 if no bound is specified' hack, though. The base < 5 convention
is a by-blow of that era.

As for the others, bounds in third party packages on template-haskell cause
an unreasonably large fraction of the user complaints I receive. An even
worse situation is where they _do_ wind up "upgrading" template-haskell and
now it doesn't work at all, silently several packages later.

That said, this should be rather mitigated going forward by:

https://github.com/hvr/cabal/commit/65e9b88bc849e76040ed7947591ea7172cd02db5

which closes out

https://github.com/haskell/cabal/issues/1444

and

https://github.com/haskell/cabal/issues/667

So in essence, it _is_ being fixed in cabal.

-Edward


On Wed, Apr 9, 2014 at 3:24 PM, Michael Snoyman <michael at snoyman.com> wrote:

> At Herbert's request, I'm splitting off this part of the PVP proposal I
> made[1] to its own separate proposal. Same discussion period of three
> weeks. The proposal is:
>
> Upper bounds should not be included on non-upgradeable packages, such as
> base and template-haskell (are there others?). Alternatively, we should
> establish some accepted upper bound on these packages, e.g. many people
> place base < 5 on their code.
>
> The purpose (elaborated in my blog post[2]) is that these upper bounds
> virtually never provide for a successful build. Instead, they are purely
> about what error messages the user receives. With this change:
>
> * Some build plans that would have previously been impossible are now
> possible, without resorting to the nuclear option of --allow-newers.
> * Instead of cabal version bound error messages, users get GHC compiler
> errors that can be fed back upstream to help get packages fixed more
> expediently.
>
> Downsides I'm aware of:
>
> * If you consider the cabal error messages more user friendly, then the
> error message quality goes down.
> * Users may find out later than they do right now about a failing build.
>
> [1] http://www.haskell.org/pipermail/libraries/2014-April/022529.html
> [2] http://www.yesodweb.com/blog/2014/04/proposal-changes-pvp
>
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