From 8828f65cb7a7a9c729d93d3d433150257f13c72f Mon Sep 17 00:00:00 2001
From: Joshua Clayton <joshua.clayton@gmail.com>
Date: Mon, 27 Jun 2016 05:55:11 -0400
Subject: [PATCH] Make reading files safer

---
 src/Unused/ResultsClassifier/Config.hs | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/Unused/ResultsClassifier/Config.hs b/src/Unused/ResultsClassifier/Config.hs
index ea09831..5621617 100644
--- a/src/Unused/ResultsClassifier/Config.hs
+++ b/src/Unused/ResultsClassifier/Config.hs
@@ -9,13 +9,13 @@ import qualified Data.ByteString.Char8 as C
 import qualified Data.Either as E
 import qualified Data.Bifunctor as B
 import System.FilePath ((</>))
-import System.Directory (getHomeDirectory)
+import System.Directory (getHomeDirectory, doesFileExist)
 import Paths_unused (getDataFileName)
 import Unused.ResultsClassifier.Types (LanguageConfiguration, ParseConfigError(..))
 import Unused.Util (readIfFileExists)
 
 loadConfig :: IO (Either String [LanguageConfiguration])
-loadConfig = Y.decodeEither <$> readConfig
+loadConfig = either Left Y.decodeEither <$> readConfig
 
 loadAllConfigurations :: IO (Either [ParseConfigError] [LanguageConfiguration])
 loadAllConfigurations = do
@@ -41,5 +41,11 @@ loadConfigFromFile path = do
 addSourceToLeft :: String -> Either String c -> Either ParseConfigError c
 addSourceToLeft source = B.first (ParseConfigError source)
 
-readConfig :: IO BS.ByteString
-readConfig = getDataFileName ("data" </> "config.yml") >>= BS.readFile
+readConfig :: IO (Either String BS.ByteString)
+readConfig = do
+    configFileName <- getDataFileName ("data" </> "config.yml")
+    exists <- doesFileExist configFileName
+
+    if exists
+        then Right <$> BS.readFile configFileName
+        else return $ Left "default config not found"