Create new haskell package _fast_

roll.hs

#!/usr/bin/env stack
-- stack --resolver lts-17.14 script

{-# language LambdaCase #-}

import System.Environment
import System.Directory
import System.FilePath

main = do
  getArgs >>= \case
    ("--name" : name : "--deps" : deps) -> do
      doMain name (["base", "mtl", "containers", "exceptions"] ++ deps)

    ["--name", name] -> do
      doMain name ["base", "mtl", "containers", "exceptions"]

    _ -> do
      print "USAGE: roll.hs --name NAME"

doMain name deps = do
  createDirectoryIfMissing True name
  createDirectoryIfMissing True (name </> "src")
  let content = contents name deps
  writeFile (name </> ".gitignore") (unlines gitignore)
  writeFile (name </> "package.yaml") content
  writeFile (name </> "src" </> "It.hs") "module It where"
  writeFile (name </> "stack.yaml") "resolver: lts-17.14"
  putStrLn content

contents name deps = chain'
  [ block "name" name
  , block "dependencies" $ list deps
  , block "default-extensions" $ list extensions
  , block "ghc-options" "-Wall -freverse-errors"
  , block "library" $ chain
    [ block "source-dirs" $ list ["src"]
    ]
  ]

block :: String -> String -> String
block header content = header ++ ": " ++ content

list :: [String] -> String
list = chain . map listItem

listItem :: String -> String
listItem = ("- " ++)

chain :: [String] -> String
chain = unlines . ("" :) . map indent . lines . unlines

chain' :: [String] -> String
chain' = unlines

indent :: String -> String
indent = ("  " ++)

extensions :: [String]
extensions =
  [ "AllowAmbiguousTypes"
  , "ApplicativeDo"
  , "BlockArguments"
  , "ConstraintKinds"
  , "DataKinds"
  , "DeriveAnyClass"
  , "DeriveFoldable"
  , "DeriveFunctor"
  , "DeriveTraversable"
  , "DerivingStrategies"
  , "DerivingVia"
  , "DuplicateRecordFields"
  , "EmptyCase"
  , "FlexibleContexts"
  , "FlexibleInstances"
  , "FunctionalDependencies"
  , "GADTs"
  , "GeneralizedNewtypeDeriving"
  , "ImportQualifiedPost"
  , "KindSignatures"
  , "LambdaCase"
  , "MultiParamTypeClasses"
  , "MultiWayIf"
  , "NamedFieldPuns"
  , "OverloadedStrings"
  , "PatternSynonyms"
  , "RankNTypes"
  , "ScopedTypeVariables"
  , "StandaloneDeriving"
  , "TemplateHaskell"
  , "TypeApplications"
  , "TypeFamilies"
  , "TypeOperators"
  , "TypeSynonymInstances"
  , "UndecidableInstances"
  , "ViewPatterns"
  , "QuasiQuotes"
  ]

gitignore :: [String]
gitignore =
  [ "dist"
  , "dist-*"
  , "cabal-dev"
  , "*.o"
  , "*.hi"
  , "*.hie"
  , "*.chi"
  , "*.chs.h"
  , "*.dyn_o"
  , "*.dyn_hi"
  , ".hpc"
  , ".hsenv"
  , ".cabal-sandbox/"
  , "cabal.sandbox.config"
  , "*.prof"
  , "*.aux"
  , "*.hp"
  , "*.eventlog"
  , ".stack-work/"
  , "cabal.project.local"
  , "cabal.project.local~"
  , ".HTF/"
  , ".ghc.environment.*"
  , "*.cabal"
  ]