Use Cabal's Distribution.Text/Distribution.Package to validate package names

yesod-bin/Scaffolding/Scaffolder.hs

@@ -15,8 +15,9 @@ import           Text.ProjectTemplate  (unpackTemplate, receiveFS)
 import           System.IO
 import           Text.Shakespeare.Text (renderTextUrl, textFile)
 import Network.HTTP.Conduit (withManager, http, parseUrl, responseBody)
-import           Data.List.Split       (splitOn)
-import           Data.Char             (isDigit)
+import           Data.Maybe            (isJust)
+import           Distribution.Text     (simpleParse)
+import           Distribution.Package  (PackageName)
 
 prompt :: (String -> Maybe a) -> IO a
 prompt f = do
@@ -61,27 +62,15 @@ backendBS Mysql = $(embedFile "hsfiles/mysql.hsfiles")
 backendBS MongoDB = $(embedFile "hsfiles/mongo.hsfiles")
 backendBS Simple = $(embedFile "hsfiles/simple.hsfiles")
 
--- | Is the character valid for a project name?
-validPN :: Char -> Bool
-validPN c
-    | 'A' <= c && c <= 'Z' = True
-    | 'a' <= c && c <= 'z' = True
-    | '0' <= c && c <= '9' = True
-validPN '-' = True
-validPN _ = False
-
--- | Cabal separates packages with a hyphen into words. A word can't consist of only digits
--- <http://www.haskell.org/ghc/docs/7.0.3/html/Cabal/packages.html Relevant Cabal Docs>
--- Fixes <https://github.com/yesodweb/yesod/issues/550 #550>
-wordsHaveOneCharacter :: String -> Bool
-wordsHaveOneCharacter s = not $ any (all isDigit) (splitOn "-" s)
+validPackageName :: String -> Bool
+validPackageName s = isJust (simpleParse s :: Maybe PackageName)
 
 scaffold :: Bool -- ^ bare directory instead of a new subdirectory?
          -> IO ()
 scaffold isBare = do
     puts $ renderTextUrl undefined $(textFile "input/welcome.cg")
     project <- prompt $ \s ->
-        if all validPN s && not (null s) && s /= "test" && wordsHaveOneCharacter s
+        if validPackageName s && s /= "test"
             then Just s
             else Nothing
     let dir = project