[Haskell-cafe] Why does cabal unnecessarily reinstall dependencies?

[Erik Hesselink]

It might be that it both your own package and the dependencies cabal
tries to reinstall all depend on some package P. If the dependencies
are installed depending on P version 1, but to satisfy all
dependencies for your own package, cabal needs them to depend on P
version 2, cabal will reinstall them (possibly breaking other packages
that depend on them; is this a bug?)

You can see if this is the case by running 'cabal install --dry-run -v'.

Erik

On Mon, Nov 22, 2010 at 22:26, Martijn van Steenbergen
<martijn at van.steenbergen.nl> wrote:
> Hello cafe,
>
> When I want to locally install my own package through "cabal install" it
> tries to reinstall dependencies convertible-1.0.9.1, HDBC-2.2.6.1 and
> HDBC-mysql-0.6.3 even though they are already installed (and work fine). Why
> does it do this?
>
> cabal-install version 0.8.2
> using version 1.8.0.2 of the Cabal library
> Mac OS Leopard
>
> Thanks,
>
> Martijn.
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