On Fri, Jun 15, 2007 at 03:06:07PM +0200, Thomas Schilling wrote:
On 15 jun 2007, at 14.09, Neil Mitchell wrote:
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?
This has the same problem, in that different versions of the same package provide different things. Also, if you install _class first and _data second then you don't get Class.InstanceForData, whereas installing them the other way round you do.
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 }
One thing I have considered proposing is rather than just exposed-modules: ... other-modules: ... we could have (I'm not particularly advocating this syntax): modules: ... modules[testing]: ... modules[internal]: ... (you can put any string inside [...]) and you can then, in another package, say depends: foo[testing,internal]
Testing for the tag is (almost) already supported:
build-depends: demo >= 1.1-debug,
IIRC tags are designed to be ignored when comparing version numbers, so this also has the same problem. Thanks Ian