cabal sandbox aware ghc wrapper

ghcs.sh

# This is a cabal-sandbox aware wrapper for GHC.
#
# To see the Template Haskell expansions in my Yesod app,
# I tried running (unseccessfully):
#
#   $ ghc -XTemplateHaskell -ddump-splices Foundation.hs
#   Foundation.hs:21:8:
#       Could not find module `Yesod.Core.Types'
#       Use -v to see a list of the files searched for.
#
# The problem is that ghc will (by default) search for
# packages in the locations listed by `ghc-pkg list`.
# But, one can grab the package db from the cabal.sandbox.config
# and pass that path directly to ghc - which is exactly what
# this function does.
#
# Enjoy!

function ghcs {
  local DIR=$PWD
  local TARGET="cabal.sandbox.config"
  while [ ! -e $DIR/$TARGET -a $DIR != "/" ]; do
    DIR=$(dirname $DIR)
  done
  if test $DIR != "/"; then
    local DB=$(sed -ne '/^package-db: */{s///p;q;}' "$DIR/$TARGET")
    ghc -no-user-package-db -package-db="$DB" "$@"
  else
    ghc "$@"
  fi
}