Use colordiff to display test results if available

1 files changed, 11 insertions, 1 deletions

diff --git a/tests/runtests.hs b/tests/runtests.hs
index 6cec7cb4..e4d676b3 100644
--- a/tests/runtests.hs
+++ b/tests/runtests.hs
@@ -9,7 +9,9 @@ import Control.Monad
 import Text.Printf
 import Text.Regex
 import Distribution.Simple.Utils
+import Distribution.Simple.Program
 import Distribution.Verbosity
+import Data.Maybe
 
 
 main = do
@@ -22,6 +24,11 @@ haddockEq file1 file2 = stripLinks file1 == stripLinks file2
     stripLinks f = subRegex (mkRegexWithOpts "<A HREF=[^>]*>" False False) f "<A HREF=\"\">"
 
 
+programOnPath p = do
+  result <- findProgramOnPath p silent
+  return (isJust result)
+
+
 check modules strict = do
   forM_ modules $ \mod -> do
     let outfile = "output" </> (dropExtension mod ++ ".html")
@@ -35,7 +42,10 @@ check modules strict = do
         if not $ haddockEq out ref
           then do
             putStrLn $ "Output for " ++ mod ++ " has changed! Exiting with diff:"
-            system $ "diff " ++ reffile ++ " " ++ outfile
+            b <- programOnPath "colordiff"
+            if b
+              then system $ "colordiff " ++ reffile ++ " " ++ outfile
+              else system $ "diff " ++ reffile ++ " " ++ outfile
             if strict then exitFailure else return ()
           else do
             putStrLn $ "Pass: " ++ mod