improve exception handling

Push it down from needing to be done in every Storer,
to being checked once inside ChunkedEncryptable.

Also, catch exceptions from PrepareStorer and PrepareRetriever,
just in case..

Remote/Directory.hs

@@ -117,7 +117,7 @@ store d chunkconfig k b p = do
 	void $ tryIO $ createDirectoryIfMissing True tmpdir
 	case chunkconfig of
 		LegacyChunks chunksize -> Legacy.store chunksize finalizer k b p tmpdir destdir
-		_ -> flip catchNonAsync (\e -> warningIO (show e) >> return False) $ do
+		_ -> do
 			let tmpf = tmpdir </> keyFile k
 			meteredWriteFile p tmpf b
 			finalizer tmpdir destdir

Remote/Helper/Chunked.hs

@@ -70,12 +70,16 @@ numChunks = pred . fromJust . keyChunkNum . fst . nextChunkKeyStream
  - the storer action, along with a corresponding chunk key and a
  - progress meter update callback.
  -
- - Note that the storer action is responsible for catching any
- - exceptions it may encounter.
- -
  - This action may be called on a chunked key. It will simply store it.
  -}
-storeChunks :: UUID -> ChunkConfig -> Key -> FilePath -> MeterUpdate -> (Key -> L.ByteString -> MeterUpdate -> IO Bool) -> Annex Bool
+storeChunks
+	:: UUID
+	-> ChunkConfig
+	-> Key
+	-> FilePath
+	-> MeterUpdate
+	-> (Key -> L.ByteString -> MeterUpdate -> IO Bool)
+	-> Annex Bool
 storeChunks u chunkconfig k f p storer = metered (Just p) k $ \meterupdate ->
 	either (\e -> warning (show e) >> return False) (go meterupdate)
 		=<< (liftIO $ tryIO $ L.readFile f)
@@ -188,7 +192,7 @@ retrieveChunks
 	-> Annex Bool
 retrieveChunks retriever u chunkconfig encryptor basek basep sink = do
 	ls <- chunkKeys u chunkconfig basek
-	liftIO $ flip catchNonAsync giveup (firstavail ls)
+	liftIO $ firstavail ls `catchNonAsync` giveup
   where
 	giveup e = do
 		warningIO (show e)

Remote/Helper/ChunkedEncryptable.hs

@@ -29,12 +29,15 @@ import Annex.Content
 import Annex.Exception
 
 -- Prepares to store a Key, and returns a Storer action if possible.
+-- May throw exceptions.
 type PrepareStorer = Key -> Annex (Maybe Storer)
 
 -- Stores a Key, which may be encrypted and/or a chunk key.
+-- May throw exceptions.
 type Storer = Key -> L.ByteString -> MeterUpdate -> IO Bool
 
 -- Prepares to retrieve a Key, and returns a Retriever action if possible.
+-- May throw exceptions.
 type PrepareRetriever = Key -> Annex (Maybe Retriever)
 
 -- Retrieves a Key, which may be encrypted and/or a chunk key.
@@ -68,8 +71,11 @@ chunkedEncryptableRemote c preparestorer prepareretriever r = encr
 	chunkconfig = chunkConfig c
 	gpgopts = getGpgEncParams encr
 
+	safely a = catchNonAsyncAnnex a (\e -> warning (show e) >> return False)
+
 	-- chunk, then encrypt, then feed to the storer
-	storeKeyGen k p enc = maybe (return False) go =<< preparestorer k
+	storeKeyGen k p enc = safely $
+		maybe (return False) go =<< preparestorer k
 	  where
 		go storer = sendAnnex k rollback $ \src ->
 			metered (Just p) k $ \p' ->
@@ -84,7 +90,7 @@ chunkedEncryptableRemote c preparestorer prepareretriever r = encr
 						storer (enck k') encb p'
 
 	-- call retriever to get chunks; decrypt them; stream to dest file
-	retrieveKeyFileGen k dest p enc =
+	retrieveKeyFileGen k dest p enc = safely $
 		maybe (return False) go =<< prepareretriever k
 	  where
 	  	go retriever = metered (Just p) k $ \p' ->