patch applied (cabal): Stop having hooks return an ExitCode that we then ignore

[Sven Panne]

On Saturday 23 June 2007 19:25, Ian Lynagh wrote:
> [...]
> However, we decided that it was best to fix the design now, while we
> were making other changes to the API and while there are relatively few
> libraries using it, than be stuck with the poor design forever.

OK, I can understand that motivation, but I thought that Cabal was a little 
bit more stable nowadays.

> Note that most of the hooks that used to return ExitCode are actually up
> for removal, as described in the links in
>     http://hackage.haskell.org/trac/hackage/ticket/134

Hmmm, is there a single place which summarizes the design of the replacement 
of the current hooks? Will there be some kind of transition roadmap? If not, 
how should we handle Alex and Happy source distros? Different Setup.lhs files 
depending on the Cabal version?

> [...] Something like this ought to do it:
>
>     myHook = do ...
>                 return done
>
>     class Done a where
>         done :: a
>
>     instance Done () where
>         done = ()
>
>     instance Done ExitCode where
>         done = ExitSuccess

A clever hack. :-) I will push updated Setup.lhs for Alex and Happy soon.

Cheers,
   S.