src/Main.hs: fix handling of "domain not found" errors.

The "not delegated" example in the man page is now failing, because
we're getting back a NameError (failure result) instead of an empty
success result. I'm not sure when this changed -- and my fix is
probably backwards-incompatible -- but I've updated haeredes to look
for the NameError rather than an empty result. The documented example
works again, but I've only tested with v3.0.2 of the "dns" library.

diff --git a/src/Main.hs b/src/Main.hs
index 89d2cd56d1a2aeaca07420d403e2e29da1e7abfe..c93697a0c7d565e431201a56c7d851e10d1f4f2e 100644 (file)
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -11,6 +11,7 @@ import qualified Data.ByteString.Char8 as BS (
   words )
 import Data.List ( (\\), intersperse )
 import Network.DNS (
+  DNSError(NameError),
   Domain,
   FileOrNumericHost(RCHostName),
   ResolvConf(resolvInfo, resolvTimeout),
@@ -52,15 +53,18 @@ report :: [Domain] -- ^ The list of @delgts@
        -> LookupResult
        -> IO ()
 
--- If the lookup resulted in a DNS error, we just ignore the whole
--- thing.
-report _ _ (_, Left _) = return ()
-
 -- If the lookup succeeded but there were no results, report that the
--- domain is not delegated.
-report _ _ (d, Right []) =
+-- domain is not delegated. Note that the behavior of the DNS library
+-- changed with regard to this at some point: we used to get back
+-- a "success," but with an empty list of results. Now a NameError
+-- (which is not actually an error!) is returned.
+report _ _ (d, Left NameError) =
   putStrLn $ "Domain " ++ (show d) ++ " not delegated."
 
+-- If the lookup resulted in some other DNS error, we just ignore the
+-- whole thing.
+report _ _ (_, Left _) = return ()
+
 -- Otherwise, subtract our delegates from the list of results and
 -- report the leftovers.
 report delgts normalize_function (d, Right raw_hosts) = do