This thread is kinda missing an important point.  

Namely that on hackage now, the admins and trustees have the power to edit the cabal files to fix broken constraints. (As do maintainers of their own packages)

Whether relaxing incorrectly conservative or over strengthening overly lax constraints, this now doesn't require a rerelease to "fix".  There are valid reasons of provinence for why that might not make sense in all case

Unless I'm missing the point, doesn't that solve most of the matter?

-carter

On Tuesday, February 25, 2014, Michael Snoyman <michael@snoyman.com> wrote:

On Tue, Feb 25, 2014 at 5:12 PM, Brandon Allbery <allbery.b@gmail.com> wrote:

On Tue, Feb 25, 2014 at 1:44 AM, Michael Snoyman <michael@snoyman.com> wrote:

But that's only one half of the "package interoperability" issue. I face this first hand on a daily basis with my Stackage maintenance. I spend far more time reporting issues of restrictive upper bounds than I do with broken builds from upstream changes. So I look at this as purely a game of statistics: are you more likely to have code break because version 1.2 of text changes the type of the map function and you didn't have an upper bound, or because two dependencies of yours have *conflicting* versions bounds on a package like aeson[2]? In my experience, the latter occurs far more often than the former.

I have a question for you.

Is it better to save a developer some work, or is it better to force that work onto end users?

Because we keep constantly seeing examples where saving the developer some upper bounds PVP work forces users to deal with unexpected errors, but since Haskell developers don't see that user pain it is considered irrelevant/nonexistent and certainly not any justification for saving developers some work.

Personally, I think any ecosystem which strongly prefers pushing versioning pain points onto end users instead of developers is doing itself a severe disservice.

Are there things that could be improved about versioning policy? Absolutely. But pushing problems onto end users is not an improvement.

I think it's a false dichotomy. I've received plenty of complaints from users about being unable to install newer versions of some dependency because a library that Yesod depends on has an unnecessary strict upper bound. Are there situations where the PVP saves a user some pain? Yes. Are there situations where the PVP causes a user some pain? Yes.

It's disingenuous to frame this as a black and white "developer vs user" issue, it's far more complex than that. After a lot of experience, I believe the PVP- or at least strict adherence to it- is a net loss.

And I think the *real* solution is something like Stackage, where curators have taken care of the versioning pain points instead of either developers or end users. Linux distributions have been doing this for a long time. 

Michael

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