⚠️ Unmaintained. Use -Wunused-packages instead.

Prune Juice

Prune unused Haskell dependencies from a Haskell project. Parses .cabal files using either stack.yaml or cabal.project (whichever is available), and ghc-pkg to load the exposed-modules fields of all the direct dependencies of the packages. Parses imports of each source file, compares against the exposed modules, and errors if any dependency listed in <package>.cabal is never imported by a source file in that package.

Quickstart

To install prune-juice from source, clone this repo and run stack install prune-juice.

From there, you can run it with prune-juice.

If you'd like prune-juice to apply changes, run it as prune-juice --apply. This will prompt you for confirmation each time it writes to a file. If you'd like to bypass that confirmation, run it as prune-juice --apply --no-verify. If you find that the applied changes are not working correctly, you can apply them in "safe" mode with prune-juice --apply --strategy safe, though this will likely change your .cabal file in other unexpected ways.

Usage

$ stack install
$ prune-juice --help
Usage: prune-juice [--project-root PROJECT_ROOT] [--no-default-ignore]
                   [--no-ignore-self] [--extra-ignore EXTRA_IGNORE]
                   [--package PACKAGE] [--verbosity VERBOSITY]
                   [--build-system BUILD_SYSTEM] [--apply] [--no-verify]
                   [--strategy ARG]
  Prune a Haskell project's dependencies

Available options:
  -h,--help                Show this help text
  --project-root PROJECT_ROOT
                           Project root (default: ".")
  --no-default-ignore      Don't use the default ignore list
                           ([base,hedgehog,hspec,hspec-discover,tasty,tasty-hedgehog,tasty-hspec,tasty-hunit])
  --no-ignore-self         Error if an executable doesn't use the library it's
                           defined with
  --extra-ignore EXTRA_IGNORE
                           Dependencies(s) to ignore in addition to the default
                           ignore list
  --package PACKAGE        Package name(s)
  --verbosity VERBOSITY    Set the verbosity level (one of
                           [silent,error,info,debug]) (default: error)
  --build-system BUILD_SYSTEM
                           Build system to use instead of inference (one of
                           [stack,cabal-project,cabal])
  --apply                  Apply changes
  --no-verify              Do not ask for verification when applying (implies
                           --apply)
  --strategy ARG           Strategy to use to apply (one of [safe,smart])
                           (default: smart)
  --version                Show version and exit

Known issues

In order for prune-juice to correctly detect local dependency usage, you have to run stack build (or other ghc-pkg registration mechanism). prune-juice does not do this for you.

prune-juice doesn't know about test discovery or Paths_-type files, so there is a mechanism to ignore these types of packages.

prune-juice doesn't know about package imports, so if a file has something like import "cryptohash" Crypto.Hash it will interpret this as an import from both cryptonite and cryptohash, if both dependencies are available.

--apply and --no-verify only work on .cabal files, so hpack/package.yaml are not supported.