[Haskell-cafe] already installed packages alerted as not being installed

[Daniel Kahlenberg]

Kazu,

thanks I wanted to mention that the "unknown symbol" error is very
likely not related to the cab tool as the same error appears, when
using the cabal - tool. I guess we can ignore it even in the context
of my main question, sorry for being to verbose. What I found more
interesting is, that cab doesn't try to re-install an installed
package - already in the database too, as ghc-pkg output pretends -
which is expected behaviour. The cabal system frontend obviously does
trying to reinstall the package though. This seems like different
model of reality...

Cheers
Daniel

2011/4/11 Kazu Yamamoto <kazu at iij.ad.jp>:
> Hello,
>
>> When I install cabal-dev and cab first and then re-install everything
>> with cab instead of cabal the issue with re-installing already
>> installed packages described above disappears and only an "unknown
>> symbol" message related to the correctly found installed cairo package
>> remains. So is there an error in package database handling somewhere
>> or changed semantics in cabal | ghc-pkg | (even) pkg-config flags I
>> missed?
>
> "cab" is just a wrapper for "cabal" and "cabal-dev" for installation.
> So, I have no idea about what's going on.
>
> Please try "cab install <package> -n" to see what will happen before
> typing "cab install <package>". If you find the word "reinstall", you
> should not install the package because the installation operation will
> break your package environment.
>
> You can analyze package dependency with:
> cab deps <package> -r
> cab revdeps <package> -r
> cab list -r
>
> Adding the "-a" option displays global packages also.
>
> I recommend to use a sandbox when you try to resolve a dependency
> problem.
>
> --Kazu
>