when xmpp connection fails, show the host(s) it tried to connect to

Assistant/XMPP/Client.hs

@@ -27,36 +27,43 @@ data XMPPCreds = XMPPCreds
 	}
 	deriving (Read, Show)
 
-connectXMPP :: XMPPCreds -> (JID -> XMPP a) -> IO (Either SomeException ())
+connectXMPP :: XMPPCreds -> (JID -> XMPP a) -> IO [(HostPort, Either SomeException ())]
 connectXMPP c a = case parseJID (xmppJID c) of
 	Nothing -> error "bad JID"
 	Just jid -> connectXMPP' jid c a
 
 {- Do a SRV lookup, but if it fails, fall back to the cached xmppHostname. -}
-connectXMPP' :: JID -> XMPPCreds -> (JID -> XMPP a) -> IO (Either SomeException ())
-connectXMPP' jid c a = go =<< lookupSRV srvrecord
+connectXMPP' :: JID -> XMPPCreds -> (JID -> XMPP a) -> IO [(HostPort, Either SomeException ())]
+connectXMPP' jid c a = reverse <$> (go [] =<< lookupSRV srvrecord)
   where
 	srvrecord = mkSRVTcp "xmpp-client" $
 		T.unpack $ strDomain $ jidDomain jid
 	serverjid = JID Nothing (jidDomain jid) Nothing
 
-	go [] = run (xmppHostname c)
-			(PortNumber $ fromIntegral $ xmppPort c)
-			(a jid)
-	go ((h,p):rest) = do
+	go l [] = do
+		let h = xmppHostname c
+		let p = PortNumber $ fromIntegral $ xmppPort c
+		r <- run h p $ a jid
+		return (r : l)
+	go l ((h,p):rest) = do
 		{- Try each SRV record in turn, until one connects,
 		 - at which point the MVar will be full. -}
 		mv <- newEmptyMVar
 		r <- run h p $ do
 			liftIO $ putMVar mv ()
 			a jid
-		ifM (isEmptyMVar mv) (go rest, return r)
+		ifM (isEmptyMVar mv)
+			( go (r : l) rest
+			, return (r : l)
+			)
 
 	{- Async exceptions are let through so the XMPP thread can
 	 - be killed. -}
-	run h p a' = tryNonAsync $
-		runClientError (Server serverjid h p) jid
-			(xmppUsername c) (xmppPassword c) (void a')
+	run h p a' = do
+		r <- tryNonAsync $
+			runClientError (Server serverjid h p) jid
+				(xmppUsername c) (xmppPassword c) (void a')
+		return ((h, p), r)
 
 {- XMPP runClient, that throws errors rather than returning an Either -}
 runClientError :: Server -> JID -> T.Text -> T.Text -> XMPP a -> IO a