I'd just like to reseruct the conversation from here (http://www.haskell.org//pipermail/libraries/2005-December/004692.html) for a quick moment if I might. At the time I wrote:

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This would greatly simplify the Distribution.Simple.UserHooks structure bringing it from 34 fields to 14 fields, or so.

Downsides: Making pre and post hooks would now be slightly harder, and it would break existing hooks-using code.

I just want to mention that these kind of changes represent represent a VERY big problem. I discussed that issue at some length in an email I intended to send to this list very recently, but it seems to have gotten lost.

Are you sure they represent a very big problem in practice and not just in theory?

[snip]

Well, obviously it isn't a practical problem yet. If it was we'd have people screaming about it on the lists.

I would now like to add to the theoretical arguments I made then the evidence that the HSQL driver package for MySQL uses the user hooks of Cabal and I have just experienced a case of Cabal version skew breaking a build system, because this package will not build for me using Cabal 1.1.3. I am unsure at the moment if this is because my Cabal is too new or too old, and I now face the prospect of 1) hacking on the build system to match my cabal, 2) trying random cabal upgrades/downgrades or 3) pinging the package maintainers to figure out how to build this package. Rob Dockins