Sample Setup.hs file for creating .lock.yaml files for Cabal based Haskell projects

Setup.hs

{-# LANGUAGE OverloadedStrings #-}
import Distribution.Simple
import Distribution.Simple.LocalBuildInfo
import Distribution.Simple.Setup
import Distribution.PackageDescription
import System.IO (writeFile)
import qualified Data.Text as T

main :: IO ()
main = defaultMainWithHooks simpleUserHooks {postConf = printLockFile}

printLockFile :: Args -> ConfigFlags -> PackageDescription -> LocalBuildInfo -> IO ()
printLockFile _ _ packageDescription localBuildInfo =
    writeFile (name ++ ".lock.yaml") $ ("components:\n" ++) $ concat $
        flip map (allComponentsInBuildOrder localBuildInfo) $
            \(compName, buildInfo) ->
                "  " ++ showComponentName compName ++ ":\n" ++
                concatMap showPkgInfo (componentPackageDeps buildInfo)
  where
    PackageName name = pkgName $ package packageDescription

    showPkgInfo :: (InstalledPackageId, PackageIdentifier) -> String
    showPkgInfo (pkgId, ipi) = "    - " ++ stripPackageHash pkgId ++ "\n" -- ++

    stripPackageHash (InstalledPackageId str) = dropDashEnding str
    dropDashEnding str = dropHash `applyAsText` str
      where
        dropHash = T.intercalate "-" . init' . T.splitOn "-"
        applyAsText f = T.unpack . f . T.pack
        init' ["builtin_rts"] = []
        init' x@(_:_:_) = init x
        init' _ = error $ "Setup.hs: init': bad package name: " ++ str