Installing packages in your test compiler

You have your compiler built, so you can use the inplace compiler to compile test programs. This lives in $(TOP)/inplace/bin/ghc-stage2 (see Commentary/SourceTree).

But sometimes a test case will require the installation of some packages from Hackage. There are two routes.

Plan A: Cabal is up to date

If your installed cabal is sufficiently up to date, you can say

cabal install --with-ghc=<inplace-ghc> --global <package>

where <inplace ghc> is the path to your inplace GHC (usually $(TOP)/inplace/bin/ghc-stage2), and <package> is the name of the package. The --global says to register the package in the global database, which for the inplace compiler is something like $(TOP)/inplace/lib/package.conf.d/.

But sometimes Cabal changes, so you might get a message like

cabal: failed to parse output of 'ghc-pkg dump'

In that case you need to use the Cabal code that comes with the new version of GHC (ie the one in your build tree). So use Plan B.

Plan B: Cabal is out of date

Go to a directory where you are happy to keep the newly-downloaded code.

cabal unpack <package>
cd <package>
<inplace-ghc> --make Setup.lhs -o Setup
./Setup configure --with-ghc=<inplace-ghc> --global <package>
./Setup build
./Setup register --inplace

The first step can be done manually, by downloading from Hackage, but it should work even with old versions of Cabal.