[Haskell-cafe] versioning of Haskell packages

[Rogan Creswick]

On Fri, Apr 29, 2011 at 3:05 PM, Daniil Elovkov
<daniil.elovkov at gmail.com> wrote:
> Hello list
>
> I have an idea on versioning of Haskell packages and a small question about
> release model of Haskell Platform. Since the latter is shorter let's start
> with it.
>
> So, what is the release model of Haskell Platform? Is it released every N
> months and frozen at that point? Or some intermediate package/compiler
> updates can make the new version to appear out of schedule?
>
> Now, about package versioning. Haskell packages are flourishing and evolving
> at a high speed. Packages depend on other package and they evolve
> asynchronously. In result it is easy to end up in need of multiple versions
> of the same package in one program or maybe stumble upon other
> conflicts/problems. I'm expressing myself a little vaguely because I don't
> have a good example in my head right now.
>
> However, the idea is to maintain not just multi-digit version names that
> don't carry any semantics except that 1.1.3 is later than 1.1.2, but also
> somehow describe compatibility between versions.
>
> This way, even if the package A has jumped from 1.0 to 1.5 and the dependent
> package B has been stagnant all this time (and B depends on A 1.0), if we
> have information that 1.5 is compatible with 1.0, then we can safely use A
> 1.5 while building B. Or we could use whatever version of A is found in the
> system as long as its compatible with A 1.0 that B depends on.

I think the PVP (Package Versioning Policy) covers a lot of what
you're discussing, but I may misunderstand:

http://www.haskell.org/haskellwiki/Package_versioning_policy

We *do* still have some trouble maintaining / enforcing the PVP in
general, and there are a few things that it doesn't cover (I don't
believe exception behavior is covered, for example, although I'd argue
that throwing more exceptions than a previous version introduces a
substantial API change. Anyhow, that's a different rant. ;).

Finer granularity would be great -- if it can be done autonomously.

I think that raising awareness of the PVP and refining the tools to
check for necessary version bumps would be a great step in the right
direction.

--Rogan