Test Cases for Configurations

[Neil Mitchell]

Hi

> I thought we'd all agreed that a library package should always export
> the same modules (and class, functions, type signatures etc), so that if
> foo depends on bar and you have bar installed then you know that you can
> build foo.
>
> In fact, I thought you were one of the people arguing in favour of this
> for the base package!

I was, for the base package. I want other people to obey these rules,
but occasionally I want to violate them :)

I'm not sure if in general it should be possible to change the export
list. Perhaps we can rely on a large number of evil stares to stop
this being common practice, and yet permit it occasionally.

One thing I would like is given a package _data, which provides a data
type, and a package _class which provides a class and various
instances, I'd like to write in the _class cabal file:

#if has _data
    module Class.InstanceForData
#endif

Perhaps configurations can support that?

Thanks

Neil