On 31 March 2005 23:15, Isaac Jones wrote:
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.
You can find the dependencies in .hi files. eg: $ ghc --show-iface Main.hi | grep '^package dep' package dependencies: base-1.0 haskell98-1.0 The dependencies for the whole library are the union of the package dependencies of the exposed modules. It should be pretty easy to implement './setup check-dependencies' in Cabal. Perhaps ghc --make could have an option to print the dependencies at the end of compilation, too. Cheers, Simon