As I understand it, Cabal hides all packages by default. If a package is not in your dependencies, it won't be available to the build, no matter the status in ghc-pkg. (Incidentally, this had neat consequences in the past, since it means that packages being hidden in ghc-pkg also does not make them unavailable to cabal. I spent some time at a previous employer attempt to debug a build failure where it turned out that the developer experiencing the failure had not pulled all the changes. In particular, we had packages A, B, and C, where C depended on A and B, and B depended on A. The developer had pulled updates to A and C, but not B. A built and installed a new version, hiding B (which was based on an old version). The developer the build C. Cabal started with everything hidden, then revealed A and B as specified by C's cabal file, and the predictable build failures resulted. I have not tried this with GHC/Cabal builds since 6.4.2, so this is probably no longer possible.) /g On Nov 20, 2007 2:18 PM, Greg Fitzgerald wrote:

Using GHC 6.8.1 on Windows XP, after having used ghc-pkg to expose 'directory-1.0.0.0', I am getting an error when I build haddock that says the package is hidden. When I type "ghc-pkg list", the package is not in parenthesis. Typing "ghc -v" says that it is using the file from "C:\ghc\ghc- 6.8.1\package.conf". That package.conf file has the 'exposed' set to True for that file. Why does GHC still think the package is hidden?

...\haddock-0.8>runhaskell Setup.lhs configure Configuring haddock-0.8...

...\haddock-0.8>runhaskell Setup.lhs build Preprocessing executables for haddock-0.8... shift/reduce conflicts: 5 Building haddock-0.8...

src/Main.hs:49:7: Could not find module `System.Directory': it is a member of package directory-1.0.0.0, which is hidden

...\haddock-0.8>ghc-pkg list C:/ghc/ghc-6.8.1\package.conf: Cabal-1.2.2.0, HUnit-1.2.0.0, OpenGL-2.2.1.1, QuickCheck-1.1.0.0, Win32-2.1.0.0, array-0.1.0.0, base-3.0.0.0, bytestring-0.9.0.1, cgi-3001.1.5.1, containers-0.1.0.0, directory-1.0.0.0, fgl-5.4.1.1, filepath-1.1.0.0, (ghc-6.8.1), haskell-src-1.0.1.1, haskell98-1.0.1.0 , hpc-0.5.0.0, html-1.0.1.1, mtl-1.1.0.0, network-2.1.0.0, old-locale-1.0.0.0, old-time-1.0.0.0, packedstring-0.1.0.0, parallel-1.0.0.0, parsec-2.1.0.0, pretty-1.0.0.0, process-1.0.0.0, random-1.0.0.0 , regex-base-0.72.0.1, regex-compat-0.71.0.1, regex-posix-0.72.0.1, rts-1.0, stm-2.1.1.0, template-haskell-2.2.0.0, time-1.1.2.0, xhtml-3000.0.2.1

Thanks, Greg

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