[Haskell-cafe] A new cabal odissey: cabal-1.8 breaking its own neck by updating its dependencies

[Jason Dagit]

On Sat, Sep 11, 2010 at 11:56 AM, Thomas DuBuisson
<thomas.dubuisson at gmail.com> wrote:

>> - is there a "specification" of which are the "core" packages?
>
> Are there packages on which the community standardizes?  That's the
> goal of Haskell-Platform [1], but I don't place any special value in a
> package being in HP yet - I just work with whatever package on Hackage
> fills my need and am under the impression this is most peoples mode of
> operation.

>From the FAQ linked by Paolo:

http://www.haskell.org/cabal/FAQ.html#dependencies-conflict

"To avoid this problem in the future, avoid upgrading core packages.
The latest version of cabal-install has disabled the upgrade command
to make it a bit harder for people to break their systems in this
way."

I think that's what Paolo meant by "core" package.  Sadly the FAQ
doesn't say what core means.  Nor is that page user editable.  I think
"core" here must refer to packages that ghc is linked to.  For
example, the process package in the example on the FAQ.

I actually had this problem last weekend and I make a habit of never
running 'cabal upgrade' and never installing things globally.  Yet
some how on my system a package that ghc was built with did get
upgraded and installed in my user package db.  It was causing various
things to fail to configure.  If I recall correctly it was the
directory package, but I'll use FOO as a place holder.  I used the
suggested command line:
ghc-pkg unregister --user FOO-X

ghc-pkg said it was ignoring the command because it would break
packages. So then I tried adding --force.   At that point, ghc-pkg
still said it was ignoring me and that I should use --force.  This was
on ghc-6.12.1.  I tried it one more time with the --force option then
ran ghc-pkg list FOO, and all instances of the FOO package were gone.
At that point I could no longer configure any packages needing FOO.
In the end I had to reinstall ghc so I took it as a chance to upgrade
to 6.12.3.

Jason