On Nov 13, 2012 6:12 PM, "Andreas Abel" <andreas.abel@ifi.lmu.de> wrote:

On 13.11.2012 17:39, Dan Burton wrote:

Mixed feelings here. I personally subscribe to the philosophy of "do one
thing and do it well"; perhaps this sort of functionality would be
better delegated to a new "curation" tool such as the one described in
Michael Snoyman's recent blog post.
http://www.yesodweb.com/blog/2012/11/solving-cabal-hell

I think Michael Snoyman's approach goes farther than mine and solves a slightly different problem.  I am not concerned with the "dependency hell" but with a means of safely avoiding bugged packages.

Uploading a bugged package can happen to anyone of us, but cabal/hackage does not provide a suitable means to rectify the situation.  Cabal's philosophy currently includes a monotonicity assumption: newer is better and more correct.  As a consequence, packages do not get removed or replaced since that could break compilation of other packages depending on a special version number of a package.  The calamity is that bugged package live on, and cabal install is oblivious of this.

If one could blacklist a certain version of a package, cabal could pick the next higher available version, as a sort of redirection mechanism to the fixed package.  For instance, if I have issued

  mylib-2.1
  mylib-2.2
  mylib-3.0

and I discover a bug in mylib-2.1, I could blacklist mylib-2.1 and upload a bugfix version

  mylib-2.1.1

that would be picked by cabal instead of mylib-2.1.

Those user packages that rely on the specific interface of mylib-2.1 (e.g. having a constraint mylib == 2.1) and do not work with mylib-2.2 would still work, since they would be built with mylib-2.1.1

On Tue, Nov 13, 2012 at 9:27 AM, Andreas Abel <andreas.abel@ifi.lmu.de
<mailto:andreas.abel@ifi.lmu.de>> wrote:

    After 2 days of shrinking 251 modules of source code to a few lines
    I realized that modify in MonadState causes <<loop>> in mtl-2.1.


    http://hackage.haskell.org/__packages/archive/mtl/2.1/doc/__html/src/Control-Monad-State-__Class.html#modify
    <http://hackage.haskell.org/packages/archive/mtl/2.1/doc/html/src/Control-Monad-State-Class.html#modify>

    The bug has been fixed, apparently seven month ago.

    https://github.com/ekmett/mtl/__pull/1
    <https://github.com/ekmett/mtl/pull/1>

    However, the "malicious" mtl-2.1 still lingers on: it is available
    from hackage and installed in many systems.

    This calls for a means of blacklisting broken or malicious packages.

       cabal update

    should also pull a blacklist of packages that will never be selected
    by cabal install (except maybe by explicit user safety overriding).

    I think such a mechanism is not only necessary for security
    purposes, but also to safe the valuable resources of our community.

    Cheers,
    Andreas

--
Andreas Abel  <><      Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.abel@ifi.lmu.de
http://www2.tcs.ifi.lmu.de/~abel/

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