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diff --git a/src/CabalHelper/Runtime/Licenses.hs b/src/CabalHelper/Runtime/Licenses.hs
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+++ b/src/CabalHelper/Runtime/Licenses.hs
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+{-# LANGUAGE CPP #-}
+
+#ifdef MIN_VERSION_Cabal
+#undef CH_MIN_VERSION_Cabal
+#define CH_MIN_VERSION_Cabal MIN_VERSION_Cabal
+#endif
+
+module CabalHelper.Runtime.Licenses (
+    displayDependencyLicenseList
+  , groupByLicense
+  , getDependencyInstalledPackageInfos
+  ) where
+
+-- Copyright (c) 2014, Jasper Van der Jeugt <m@jaspervdj.be>
+
+--------------------------------------------------------------------------------
+import Control.Arrow ((***), (&&&))
+import Control.Monad (forM_, unless)
+import Data.List (foldl', sort)
+import Data.Maybe (catMaybes)
+import Data.Set (Set)
+import qualified Data.Set as Set
+import System.Directory (getDirectoryContents)
+import System.Exit (exitFailure)
+import System.FilePath (takeExtension)
+import System.IO (hPutStrLn, stderr)
+
+import Distribution.InstalledPackageInfo
+import Distribution.License
+import Distribution.Package
+import Distribution.Simple.Configure
+import Distribution.Simple.LocalBuildInfo
+import Distribution.Simple.PackageIndex
+import Distribution.Text
+import Distribution.ModuleName
+import Distribution.Version (Version)
+--------------------------------------------------------------------------------
+
+
+
+#if CH_MIN_VERSION_Cabal(1,23,0)
+-- CPP > 1.22
+type CPackageIndex a = PackageIndex (InstalledPackageInfo)
+#elif CH_MIN_VERSION_Cabal(1,22,0)
+-- CPP >= 1.22
+type CPackageIndex a = PackageIndex (InstalledPackageInfo_ a)
+#else
+type CPackageIndex a = PackageIndex
+#endif
+
+#if CH_MIN_VERSION_Cabal(1,23,0)
+-- CPP >= 1.23
+type CInstalledPackageId = UnitId
+lookupInstalledPackageId' :: PackageIndex a -> UnitId -> Maybe a
+lookupInstalledPackageId' = lookupUnitId
+#else
+type CInstalledPackageId = InstalledPackageId
+lookupInstalledPackageId' = lookupInstalledPackageId
+#endif
+
+findTransitiveDependencies
+    :: CPackageIndex Distribution.ModuleName.ModuleName
+    -> Set CInstalledPackageId
+    -> Set CInstalledPackageId
+findTransitiveDependencies pkgIdx set0 = go Set.empty (Set.toList set0)
+  where
+    go set []  = set
+    go set (q : queue)
+        | q `Set.member` set = go set queue
+        | otherwise          =
+            case lookupInstalledPackageId' pkgIdx q of
+                Nothing  ->
+                    -- Not found can mean that the package still needs to be
+                    -- installed (e.g. a component of the target cabal package).
+                    -- We can ignore those.
+                    go set queue
+                Just ipi ->
+                    go (Set.insert q set) (Distribution.InstalledPackageInfo.depends ipi ++ queue)
+
+
+--------------------------------------------------------------------------------
+getDependencyInstalledPackageIds
+    :: LocalBuildInfo -> Set CInstalledPackageId
+getDependencyInstalledPackageIds lbi =
+    findTransitiveDependencies (installedPkgs lbi) $
+      Set.fromList $ map fst $ externalPackageDeps lbi
+
+--------------------------------------------------------------------------------
+getDependencyInstalledPackageInfos
+    :: LocalBuildInfo -> [InstalledPackageInfo]
+getDependencyInstalledPackageInfos lbi = catMaybes $
+    map (lookupInstalledPackageId' pkgIdx) $
+    Set.toList (getDependencyInstalledPackageIds lbi)
+  where
+    pkgIdx = installedPkgs lbi
+
+
+--------------------------------------------------------------------------------
+groupByLicense
+    :: [InstalledPackageInfo]
+    -> [(License, [InstalledPackageInfo])]
+groupByLicense = foldl'
+    (\assoc ipi -> insertAList (license ipi) ipi assoc) []
+  where
+    -- 'Cabal.License' doesn't have an 'Ord' instance so we need to use an
+    -- association list instead of 'Map'. The number of licenses probably won't
+    -- exceed 100 so I think we're alright.
+    insertAList :: Eq k => k -> v -> [(k, [v])] -> [(k, [v])]
+    insertAList k v []   = [(k, [v])]
+    insertAList k v ((k', vs) : kvs)
+        | k == k'   = (k, v : vs) : kvs
+        | otherwise = (k', vs) : insertAList k v kvs
+
+
+--------------------------------------------------------------------------------
+displayDependencyLicenseList
+    :: [(License, [InstalledPackageInfo])]
+    -> [(String, [(String, Version)])]
+displayDependencyLicenseList =
+    map (display *** map (getName &&& getVersion))
+  where
+    getName =
+        display . pkgName . sourcePackageId
+    getVersion =
+        pkgVersion . sourcePackageId