Long-term success of Cabal configurations? (was: Stability vs latest features)

[Thomas Schilling]

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On 15 aug 2007, at 20.20, Stefan O'Rear wrote:
>
> I'd much prefer a situation where the (much smaller number of) library
> authors carry the burden of compatibility; maybe something like
>
> {- in base-2.0's .cabal -}
>
> Provides: fps-1.0 by { Data.ByteString* }
>
> ... which unfortunately doesn't handle splits (FiniteMap etc) anywhere
> near as well.

How far would re-exporting imported modules bring us?  This would  
allow some sort of "virtual" packages (put in quotes, because I don't  
know how much this reflects the usage of this term in, e.g., Gentoo),  
which could at least solve package splits quite nicely.

Assume we have base-2.0.  Then the .cabal for base-1.0 could look  
somewhat like:

   build-depends: base >= 2.0, filepath, {- ... -}
   exposed-modules: Data.ByteString*, System.FilePath*, {- ... -}

I really don't like hacks with configurations like

   if flag(small_base) {
     build-depends: base >= 2.0, filepath >= 1.0, ...
   } else {
     build-depenhs: base >= 1.0 && base < 2.0
   }

since they have to be put in _every_ .cabal file.

/ Thomas
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