exposed packages and cabal depends

[Isaac Jones]

Ian Lynagh mentioned this problem to me a few weeks ago and Alex's
thread reminded me of it.  This doesn't really relate to Alex's
proposal, so I'm starting a new thread.

Let's say that from GHC's perspective, package A is exposed and
package B is hidden.  Angela Author creates package C which
build-depends on both A and B.  She incorrectly lists the
build-depends on B, but not on A.  While building, she doesn't notice,
since A is an exposed package.

This kinda sucks, since it would be nice to check build-dependencies
at build time.  This is very similar to the situation in Debian where
a packager doesn't realize that there's a build-dependency on A, since
she's already got it installed, but when the auto-builders get to it,
the build fails since they don't have A installed.

I don't know how to solve this; is there a way to require explicit
-package flags for all packages in ghc 6.4?  If there were, say
-fhide-all-packages, then cabal could use that while building and
Angela would catch the error of her ways much earlier.

I think the situation for "run-time" dependencies is similar.


peace,

  isaac