From f15ba81e770a432268e04bd0062eaf6e4ee88293 Mon Sep 17 00:00:00 2001
From: Duncan Coutts <duncan@community.haskell.org>
Date: Thu, 10 Feb 2011 20:01:11 +0000
Subject: [PATCH] Fix HcPkg.dump for the case of an empty database Previously
 it returned the value [emptyInstalledPackageInfo]

---
 Distribution/Simple/Program/HcPkg.hs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Distribution/Simple/Program/HcPkg.hs b/Distribution/Simple/Program/HcPkg.hs
index a884d019371..465a03baa44 100644
--- a/Distribution/Simple/Program/HcPkg.hs
+++ b/Distribution/Simple/Program/HcPkg.hs
@@ -51,6 +51,8 @@ import Distribution.Verbosity
 import Distribution.Compat.Exception
          ( catchExit )
 
+import Data.Char
+         ( isSpace )
 import Control.Monad
          ( liftM )
 
@@ -135,8 +137,12 @@ dump verbosity hcPkg packagedb = do
     --TODO: this could be a lot faster. We're doing normaliseLineEndings twice
     -- and converting back and forth with lines/unlines.
     splitPkgs :: String -> [String]
-    splitPkgs = map unlines . splitWith ("---" ==) . lines
+    splitPkgs = checkEmpty . map unlines . splitWith ("---" ==) . lines
       where
+        -- Handle the case of there being no packages at all.
+        checkEmpty [s] | all isSpace s = []
+        checkEmpty ss                  = ss
+
         splitWith :: (a -> Bool) -> [a] -> [[a]]
         splitWith p xs = ys : case zs of
                            []   -> []