Test Cases for Configurations

[Neil Mitchell]

Hi

Yes, that's much better than what I was thinking! It also allows me to
write my library and provide (or not) the flag when using GHC - so I
can explicitly choose whether to require the extra features or not.

Thanks

Neil

On 6/15/07, Thomas Schilling <nominolo at googlemail.com> wrote:
>
> On 15 jun 2007, at 14.09, Neil Mitchell wrote:
>
> > 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?
> >
>
> You mean like this?
>
> Name: demo
> Cabal-version: >= 1.3
>
> Description: This is a test file
>    with a description longer than two lines.
>
> flag Debug {
>    Description: Enable debug information
>    Default: False
> }
>
> library {
>    build-depends: blub
>    exposed-modules: Demo.Main, Demo
>
>    if flag(debug) {
>      build-depends: hunit
>      ghc-options: -DDEBUG
>      exposed-modules: Demo.Internal
>    }
> }
>
> executable foo-bar {
>    Main-is: Foo.hs
> }
>
> Of course in this case we'd need to add some flags to the version
> number, to indicate, that tho installed version has a certain feature
> enabled.
>
> This could be solved with a different package name of course, but I
> think it should be easy to add tags to a package version number:
>
>    if flag(debug) {
>      build-depends: hunit
>      ghc-options: -DDEBUG
>      tag: debug
>      exposed-modules: Demo.Internal
>    }
>
> Testing for the tag is (almost) already supported:
>
>    build-depends: demo >= 1.1-debug,
>
> It should be used often, but it could if necessary.
>
>