Force `stack` to rebuild an installed package

Question

I often install a package which depends on external libraries and manage to move those external libraries to other locations afterwards, so that compiled programs exit with

Answer 1

Update:

Based on @Michael Snoyman's comment just using this command should be enough to remove the package:

stack exec -- ghc-pkg unregister --force regex-pcre

Original Answer:

I don't know if it's the sanctioned way to do it, but it seems to work. Here is a synopsis:

1. Locate the ghc-pkg program for the version of GHC you are using
2. Locate the package-db directory for your resolver version
3. Run $ghcpkg --package-db $pkgdb unregister --force <package>
4. Also remove the package file from stack's precompiled directory

Suppose the package we want to remove is zlib-0.5.4.2.

Locating ghc-pkg

Under ~/.stack/programs find the ghc-pkg program appropriate for your compiler version, e.g. ~/.stack/programs/x86_64-osx/ghc-7.10.2/bin/ghc-pkg. Call this $ghcpkg

Locating the package db

Under ~/.stack/snapshots find the pkgdb directory for the resolver you are using, e.g. ~/.stack/snapshots/x86_64-osx/lts-3.1/7.10.2/pkgdb. Call this $pkgdb.

Unregister the package

Run:

$ghcpkg --package-db $pkgdb unregister --force zlib-0.5.4.2

Ignore any warnings about broken or breaking packages.

You can check to see if your package is registered or not with this command:

$ghcpkg --package-db $pkgdb list | grep zlib

Remove the package from the precompiled directory

Under ~/.stack/precompiled locate any directories named zlib-0.5.4.2 and remove the one for your the relevant version of GHC:

find ~/.stack/precompiled -name 'zlib-*'
/bin/rm -rf ...

Reinstall the package

stack --resolver=... install zlib

Stack should report that it is rebuilding the package.