On Jun 18, 2:24 pm, "Jean-Philippe Bernardy" <[EMAIL PROTECTED]>
wrote:
> On Wed, Jun 18, 2008 at 2:27 PM, Duncan Coutts <[EMAIL PROTECTED]> wrote:
> > Wed Jun 18 13:22:02 BST 2008 Duncan Coutts <[EMAIL PROTECTED]>
> > * Specifying cabal-version: >=1.5 is not necessary
> > yi.cabal can be processed fine with Cabal-1.2.3.0
>
> Actually we'd like to build yi with the same version as the one we link
> against,
> so we can open the build-info.
> I comitted an adapted patch.
Ok, well just make sure you do not distribute it like that. It's far
too fragile to specify one exact version.
Another thing to note is that cabal-install does not track the cabal-
version as a dependency so it the user does not happen to have 1.4.0.1
then it will just fail. It will not go and install version 1.4.0.1.
On a related note, while cabal-install can now install yi-0.3 from
hackage it cannot install 0.4 from darcs because it ends up using two
versions of Cabal. The dependency resolution system is designed to
avoid using multiple versions of dependencies so it cannot find a
solution for yi-0.4. The issue is that cabal-install does not know
that it's ok for yi to depend on one version of Cabal while the ghc
package depends on another. As it happens, it is ok because the ghc
doesn't re-export much stuff from Cabal so you don't tend to bump into
type errors but cabal-install does not have enough information
currently to know that ghc uses Cabal privately.
So just after making it work for the last set of problem we find
there's no easy solution again. :-(
The workaround is to do the configure, build and install steps
separately and avoid ever trying to make an install plan (since that
is impossible).
The longer term solution is for ghc and Cabal to support a notion of a
private build dependency, which is one where things defined in the
dependent package are not re-exported, so it would not matter what
version was used and it would not have to match the version of other
public uses of that package name.
Duncan
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