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diff --git a/vendor/cabal-helper-0.8.1.2/src/CabalHelper/Shared/Sandbox.hs b/vendor/cabal-helper-0.8.1.2/src/CabalHelper/Shared/Sandbox.hs
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+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015-2017  Daniel Gröber <cabal-helper@dxld.at>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation, either version 3 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-|
+Module      : CabalHelper.Shared.Sandbox
+Description : Extracting information from @cabal.sandbox.config@ files
+License     : GPL-3
+-}
+
+module CabalHelper.Shared.Sandbox where
+
+import Control.Applicative
+import Data.Char
+import Data.Maybe
+import Data.List
+import Data.Version
+import System.FilePath
+import System.Directory
+import Prelude
+
+import qualified Data.Traversable as T
+
+-- | Get the path to the sandbox package-db in a project
+getSandboxPkgDb :: FilePath
+             -- ^ Path to the cabal package root directory (containing the
+             -- @cabal.sandbox.config@ file)
+             -> String
+             -- ^ Cabal build platform, i.e. @buildPlatform@
+             -> Version
+             -- ^ GHC version (@cProjectVersion@ is your friend)
+             -> IO (Maybe FilePath)
+getSandboxPkgDb d platform ghcVer = do
+  mConf <- T.traverse readFile =<< mightExist (d </> "cabal.sandbox.config")
+  return $ fixPkgDbVer <$> (extractSandboxDbDir =<< mConf)
+
+ where
+   fixPkgDbVer dir =
+       case takeFileName dir == ghcSandboxPkgDbDir platform ghcVer of
+         True -> dir
+         False -> takeDirectory dir </> ghcSandboxPkgDbDir platform ghcVer
+
+ghcSandboxPkgDbDir :: String -> Version -> String
+ghcSandboxPkgDbDir platform ghcVer =
+   platform ++ "-ghc-" ++ showVersion ghcVer ++ "-packages.conf.d"
+
+-- | Extract the sandbox package db directory from the cabal.sandbox.config
+-- file. Exception is thrown if the sandbox config file is broken.
+extractSandboxDbDir :: String -> Maybe FilePath
+extractSandboxDbDir conf = extractValue <$> parse conf
+  where
+    key = "package-db:"
+    keyLen = length key
+
+    parse = listToMaybe . filter (key `isPrefixOf`) . lines
+    extractValue = CabalHelper.Shared.Sandbox.dropWhileEnd isSpace . dropWhile isSpace . drop keyLen
+
+
+mightExist :: FilePath -> IO (Maybe FilePath)
+mightExist f = do
+  exists <- doesFileExist f
+  return $ if exists then (Just f) else (Nothing)
+
+-- dropWhileEnd is not provided prior to base 4.5.0.0.
+dropWhileEnd :: (a -> Bool) -> [a] -> [a]
+dropWhileEnd p = foldr (\x xs -> if p x && null xs then [] else x : xs) []