catch whereisKey exception and provide error messages when external programs neglect to

* whereis: If a remote fails to report on urls where a key
  is located, display a warning, rather than giving up and not displaying
  any information.
* When external special remotes fail but neglect to provide an error
  message, say what request failed, which is better than displaying an
  empty error message to the user.

CHANGELOG

@@ -1,6 +1,12 @@
 git-annex (8.20200227) UNRELEASED; urgency=medium
 
   * Bugfix: Don't ignore --debug when it is followed by -c.
+  * whereis: If a remote fails to report on urls where a key
+    is located, display a warning, rather than giving up and not displaying
+    any information.
+  * When external special remotes fail but neglect to provide an error
+    message, say what request failed, which is better than displaying an
+    empty error message to the user.
 
  -- Joey Hess <id@joeyh.name>  Thu, 27 Feb 2020 00:44:11 -0400
 

Command/Whereis.hs

@@ -92,7 +92,18 @@ getRemoteUrls key remote
 		<$> askremote
 		<*> claimedurls
   where
-	askremote = maybe (pure []) (flip id key) (whereisKey remote)
+	askremote = case whereisKey remote of
+		Nothing -> pure []
+		Just w -> tryNonAsync (w key) >>= \case
+			Right l -> pure l
+			Left e -> do
+				warning $ unwords
+					[ "unable to query remote"
+					, name remote
+					, "for urls:"
+					, show e
+					]
+				return []
 	claimedurls = do
 		us <- map fst 
 			. filter (\(_, d) -> d == OtherDownloader)

Remote/External.hs

@@ -183,7 +183,8 @@ externalSetup _ mu _ c gc = do
 				=<< strictRemoteConfigParser external
 			handleRequest external INITREMOTE Nothing $ \resp -> case resp of
 				INITREMOTE_SUCCESS -> result ()
-				INITREMOTE_FAILURE errmsg -> Just $ giveup errmsg
+				INITREMOTE_FAILURE errmsg -> Just $ giveup $
+					respErrorMessage "INITREMOTE" errmsg
 				_ -> Nothing
 			-- Any config changes the external made before
 			-- responding to INITREMOTE need to be applied to
@@ -218,7 +219,7 @@ storeKeyM external = fileStorer $ \k f p ->
 			TRANSFER_SUCCESS Upload k' | k == k' -> result True
 			TRANSFER_FAILURE Upload k' errmsg | k == k' ->
 				Just $ do
-					warning errmsg
+					warning $ respErrorMessage "TRANSFER" errmsg
 					return (Result False)
 			_ -> Nothing
 
@@ -229,7 +230,8 @@ retrieveKeyFileM external = fileRetriever $ \d k p ->
 			TRANSFER_SUCCESS Download k'
 				| k == k' -> result ()
 			TRANSFER_FAILURE Download k' errmsg
-				| k == k' -> Just $ giveup errmsg
+				| k == k' -> Just $ giveup $
+					respErrorMessage "TRANSFER" errmsg
 			_ -> Nothing
 
 removeKeyM :: External -> Remover
@@ -240,7 +242,7 @@ removeKeyM external k = safely $
 				| k == k' -> result True
 			REMOVE_FAILURE k' errmsg
 				| k == k' -> Just $ do
-					warning errmsg
+					warning $ respErrorMessage "REMOVE" errmsg
 					return (Result False)
 			_ -> Nothing
 
@@ -254,7 +256,8 @@ checkPresentM external k = either giveup id <$> go
 			CHECKPRESENT_FAILURE k'
 				| k' == k -> result $ Right False
 			CHECKPRESENT_UNKNOWN k' errmsg
-				| k' == k -> result $ Left errmsg
+				| k' == k -> result $ Left $
+					respErrorMessage "CHECKPRESENT" errmsg
 			_ -> Nothing
 
 whereisKeyM :: External -> Key -> Annex [String]
@@ -270,7 +273,7 @@ storeExportM external f k loc p = safely $
 		TRANSFER_SUCCESS Upload k' | k == k' -> result True
 		TRANSFER_FAILURE Upload k' errmsg | k == k' ->
 			Just $ do
-				warning errmsg
+				warning $ respErrorMessage "TRANSFER" errmsg
 				return (Result False)
 		UNSUPPORTED_REQUEST -> Just $ do
 			warning "TRANSFEREXPORT not implemented by external special remote"
@@ -286,7 +289,7 @@ retrieveExportM external k loc d p = safely $
 			| k == k' -> result True
 		TRANSFER_FAILURE Download k' errmsg
 			| k == k' -> Just $ do
-				warning errmsg
+				warning $ respErrorMessage "TRANSFER" errmsg
 				return (Result False)
 		UNSUPPORTED_REQUEST -> Just $ do
 			warning "TRANSFEREXPORT not implemented by external special remote"
@@ -304,7 +307,8 @@ checkPresentExportM external k loc = either giveup id <$> go
 		CHECKPRESENT_FAILURE k'
 			| k' == k -> result $ Right False
 		CHECKPRESENT_UNKNOWN k' errmsg
-			| k' == k -> result $ Left errmsg
+			| k' == k -> result $ Left $
+				respErrorMessage "CHECKPRESENT" errmsg
 		UNSUPPORTED_REQUEST -> result $
 			Left "CHECKPRESENTEXPORT not implemented by external special remote"
 		_ -> Nothing
@@ -316,7 +320,7 @@ removeExportM external k loc = safely $
 			| k == k' -> result True
 		REMOVE_FAILURE k' errmsg
 			| k == k' -> Just $ do
-				warning errmsg
+				warning $ respErrorMessage "REMOVE" errmsg
 				return (Result False)
 		UNSUPPORTED_REQUEST -> Just $ do
 			warning "REMOVEEXPORT not implemented by external special remote"
@@ -684,13 +688,19 @@ checkPrepared st external = do
 						setprepared Prepared
 						return (Result ())
 					PREPARE_FAILURE errmsg -> Just $ do
-						setprepared $ FailedPrepare errmsg
-						giveup errmsg
+						let errmsg' = respErrorMessage "PREPARE" errmsg
+						setprepared $ FailedPrepare errmsg'
+						giveup errmsg'
 					_ -> Nothing
   where
 	setprepared status = liftIO $ atomically $ void $
 		swapTVar (externalPrepared st) status
 
+respErrorMessage :: String -> String -> String
+respErrorMessage req err
+	| null err = req ++ " failed with no reason given"
+	| otherwise = err
+
 {- Caches the cost in the git config to avoid needing to start up an
  - external special remote every time time just to ask it what its
  - cost is. -}
@@ -743,7 +753,8 @@ checkUrlM external url =
 		CHECKURL_CONTENTS sz f -> result $ UrlContents sz $
 			if null f then Nothing else Just $ mkSafeFilePath f
 		CHECKURL_MULTI l -> result $ UrlMulti $ map mkmulti l
-		CHECKURL_FAILURE errmsg -> Just $ giveup errmsg
+		CHECKURL_FAILURE errmsg -> Just $ giveup $
+			respErrorMessage "CHECKURL" errmsg
 		UNSUPPORTED_REQUEST -> giveup "CHECKURL not implemented by external special remote"
 		_ -> Nothing
   where