Weeder Nix

Produce a weeder check for a list of Haskell Packages from Nix

Quick Start

Add this repository as a flake:

{
  inputs = {
    weeder-nix.url = "github:NorfairKing/weeder-nix";
  };
}

Make a weeder check

{
  outputs = { self, weeder-nix }: {
    checks.x86-64_linux.dependency-graph = weeder-nix.lib.x86_64-linux.makeWeederCheck {
      haskellPackages = pkgs.haskellPackages;
      packages = [
        "foobar"
        "foobar-gen"
      ];
    };
  };
}

API Reference

makeWeederCheck

Make a weeder check for given Haskell Packages. (This does the addHieOutput handling for you, and the buildTestsWithoutRunning handling when includeTests is set.)

Arguments:

• name: Name of the check derivation

• weederToml: Path to the weeder.toml configuration file.

• packages: List of package names to make the check for.

• haskellPackages: haskellPackages to get those packages from.

• reportOnly: Don't fail if weeds are found, but instead succeed and create a report of the weeds instead.

• extraArgs: Extra command-line arguments for the weeder invocation.

• includeTests: Whether to also feed weeder the .hie files of test (and benchmark) code. Defaults to false.

  When false (the default), weeder only sees non-test code, so code that is used only by tests is reported as a weed. When true, the test suite's code is compiled (without running it) and its .hie files are included as well, so anything the tests use counts as used.

  Note: with includeTests = false, the only roots weeder has are the ones in your weeder.toml (by default Main.main and Paths_*). For a library package whose public API is exercised only by its own test suite, you'll want to declare the exposed modules as roots (e.g. with root-modules), otherwise excluding the test code makes the whole library look like a weed.

See ./nix/weederCheckFor.nix for the available arguments.

weederCheckFor

Make a weeder check based on raw packages. This assumes you've used something like addHieOutput. You probably don't need to use this.

See ./nix/weederCheckFor.nix.

addHieOutput

Add a .hie output to a Haskell package. This adds -fwrite-ide-info and collects the resulting .hie files into a separate output. You probably don't need to use this directly; makeWeederCheck does it for you.

See ./nix/addHieOutput.nix.

buildTestsWithoutRunning

Build test code without running the test suite.

Cabal doesn't build testing code unless tests are turned on. This function enables doCheck (so test code is compiled and test dependencies are available) but sets checkPhase to "" so the test suite is not executed.

This is useful when you want .hie files for test code (for weeder) without paying the cost of running the tests.

If you apply addHieOutput to your packages yourself (instead of using makeWeederCheck), you can use this function to compile test code without running it:

myPackage = buildTestsWithoutRunning (addHieOutput haskellPackages.myPackage);

See ./nix/buildTestsWithoutRunning.nix.

disableOptimisation

Disable optimisation for a Haskell package.

Weeder only needs .hie files, so there is no point spending time on optimisation. This function adds -O0, -fignore-interface-pragmas, and -fomit-interface-pragmas. makeWeederCheck applies this automatically.

See ./nix/disableOptimisation.nix.