Cabal Sandbox Cheat

Using sandboxes is simple: if you already know how to use the cabal tool to build your packages, you only need to learn a few additional commands. To initialise a fresh sandbox in the current directory, run cabal sandbox init. All subsequent commands (such as build and install) from this point will use the sandbox.

$ cd /path/to/my/haskell/library
$ cabal sandbox init                   # Initialise the sandbox
$ cabal install --only-dependencies    # Install dependencies into the sandbox
$ cabal build                          # Build your package inside the sandbox

It can be useful to make a source package available for installation in the sandbox - for example, if your package depends on a patched or an unreleased version of a library. This can be done with the cabal sandbox add-source command - think of it as “local Hackage”. If an add-source dependency is later modified, it is reinstalled automatically.

$ cabal sandbox add-source /my/patched/library # Add a new add-source dependency
$ cabal install --dependencies-only            # Install it into the sandbox
$ cabal build                                  # Build the local package
$ $EDITOR /my/patched/library/Source.hs        # Modify the add-source dependency
$ cabal build                                  # Modified dependency is automatically reinstalled

Sometimes one wants to share a single sandbox between multiple packages. This can be easily done with the --sandbox option:

$ cd /path/to/shared-sandbox
$ cabal sandbox init --sandbox .
$ cd /path/to/package-a
$ cabal sandbox init --sandbox /path/to/shared-sandbox
$ cd /path/to/package-b
$ cabal sandbox init --sandbox /path/to/shared-sandbox

To unregister a package, use cabal sandbox hc-pkg

$ cabal sandbox hc-pkg unregister story-board