[Haskell-cafe] Cabal hell

Alexey Shmalko rasen.dubi at gmail.com
Thu Apr 9 17:37:14 UTC 2015

As far as I understand PVP, you can't rely on any C. Only which are
greater-equal to one you tested your package with. It's because minor
version can introduce changes that are not forward-compatible.

So basically, PVP is Qt versioning scheme with two first numbers being
Major, third one being Minor and the rest is Patch.

If such convention already exists, what's left is to invent the way to
enforce it.

On Thu, Apr 9, 2015 at 8:28 PM, Michal Antkiewicz <mantkiew at gsd.uwaterloo.ca
> wrote:

> Well if the package X you depend on adheres to PVP [1]
> then you depend on it like this to allow newer minor versions:
> x == A.B.*
> where
> "*A.B* is known as the *major* version number, and *C* the *minor*
> version number."
> If only every package maintainer adhered to this, we'd be in much better
> shape.
> Michal
> [1] https://wiki.haskell.org/Package_versioning_policy
> On Thu, Apr 9, 2015 at 1:24 PM, Alexey Shmalko <rasen.dubi at gmail.com>
> wrote:
>> I really love Qt versioning scheme when applied to compatibility [1].
>> Given version is Major.Minor.Patch:
>> Major releases may break backwards binary and source compatibility,
>> although source compatibility may be maintained.
>> Minor releases are backwards binary and source compatible.
>> Patch releases are both backwards and forwards binary and source
>> compatible.
>> So that you know your package will work with any Qt version that has the
>> same major version and minor version is greater-equal to the one you
>> developed your package with. It would be really great if everyone followed
>> this scheme.
>> As a drawback I can note that this requires strict discipline from a
>> library developer. It's also harder to get binary compatibility right for
>> Haskell because of cross-module optimization GHC does.
>> [1] https://wiki.qt.io/Qt-Version-Compatibility
>> On Thu, Apr 9, 2015 at 7:44 PM, Patrick Redmond <plredmond at gmail.com>
>> wrote:
>>> Since learning Haskell I've had the pleasure of finding my way out of a
>>> cabal hell or two. I've developed some knowledge to cope with it [1], but
>>> mostly concluded that if I can avoid burdening my projects
>>> with dependencies that have many of their own dependencies, then cabal hell
>>> can be averted. This puts somewhat of a damper on the joy of haskell's
>>> composability.
>>> With the new release of GHC I've observed a flurry of discussion on
>>> haskell mailing lists and from Linux distro maintainers about all the
>>> fixing and patching required to keep the haskell ecosystem going.
>>> Meanwhile I've learned other languages and used other tools that don't
>>> seem to have this problem that haskell does. For example, in the elm-lang
>>> community the package management tool enforces strict api-versioning, and
>>> in the clojure ecosystem people talk about "repeatability" and achieve it
>>> by using mostly exact-version requirements, even including the language
>>> (the language version is a dependency of a project, rather than a
>>> constraint of the environment).
>>> I guess I'm wondering why we don't try something simpler to solve the
>>> haskell cabal hell problem. How about using minimum version dependencies
>>> only, not ranges, since we can't accurately guess about the future
>>> compatibility of our projects. How about automatic api-versioning of our
>>> projects to give the version numbers some rigid semantics with regard to
>>> package compatibility?
>>> [1] http://f06code.com/post/90205977959/cabal-usage-notes
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