rsstorage: return original resolver err when S3 upload fails during P…

…ut()

When the resolver failed before, a generic S3 upload error was returned,
"Something went wrong uploading to S3", which was both hard to error
handle and misleading (because it failed before even attempting to upload).

pkg/rsstorage/servers/s3server/server.go

@@ -251,17 +251,17 @@ func (s *StorageServer) Put(resolve types.Resolver, dir, address string) (string
 	// Resolve (read) the item using the piped writer
 	var wdir string
 	var waddress string
+	var resolverErr error
 	go func() {
 		// Make sure an EOF gets sent to the pipe writer. Without this, we end
 		// up hanging forever while the uploader reads from the pipe.
-		var err error
-		wdir, waddress, err = resolve(w)
-		if err != nil {
-			w.CloseWithError(err)
+		wdir, waddress, resolverErr = resolve(w)
+		if resolverErr != nil {
+			_ = w.CloseWithError(resolverErr)
 			return
 		}
 		// Close with EOF if successful
-		w.CloseWithError(io.EOF)
+		_ = w.CloseWithError(io.EOF)
 	}()
 
 	// Upload to a temporary S3 address using the piped reader
@@ -274,6 +274,11 @@ func (s *StorageServer) Put(resolve types.Resolver, dir, address string) (string
 
 	if err != nil {
 		cancel()
+		// If the upload failed because of a resolver error, return the original error
+		// instead of a generic upload error
+		if resolverErr != nil {
+			return "", "", resolverErr
+		}
 		return "", "", err
 	}
 

pkg/rsstorage/servers/s3server/server_test.go

@@ -162,6 +162,8 @@ func (s *fakeS3) Upload(input *s3manager.UploadInput, ctx context.Context, optio
 		s.address = *input.Key
 
 	}
+	// If there's an upload error, copy anyway to ensure that the resolver runs
+	_, _ = io.Copy(io.Discard, input.Body)
 	return s.upload, s.uploadErr
 }
 
@@ -419,7 +421,7 @@ func (s *S3StorageServerSuite) TestPut(c *check.C) {
 	c.Assert(err, check.ErrorMatches, "upload error")
 
 	// Resolve error
-	svc.uploadErr = nil
+	svc.uploadErr = errors.New("upload error (should not be returned)")
 	resolver = func(w io.Writer) (string, string, error) {
 		return "", "", errors.New("resolver error")
 	}