fixes tus#388

Responses to the pre-finish hook will be passed to the client as custom header "X-pre-finish-response"

cmd/tusd/cli/hooks.go

@@ -20,27 +20,31 @@ func hookTypeInSlice(a hooks.HookType, list []hooks.HookType) bool {
 	return false
 }
 
-func hookCallback(typ hooks.HookType, info handler.HookEvent) error {
-	if output, err := invokeHookSync(typ, info, true); err != nil {
+func hookCallback(typ hooks.HookType, info handler.HookEvent, captureOutput bool) (error, []byte) {
+	output, err := invokeHookSync(typ, info, true)
+	if err != nil {
 		if hookErr, ok := err.(hooks.HookError); ok {
 			return hooks.NewHookError(
 				fmt.Errorf("%s hook failed: %s", typ, err),
 				hookErr.StatusCode(),
 				hookErr.Body(),
-			)
+			), nil
 		}
-		return fmt.Errorf("%s hook failed: %s\n%s", typ, err, string(output))
+		return fmt.Errorf("%s hook failed: %s\n%s", typ, err, string(output)), nil
 	}
-
-	return nil
+	if captureOutput {
+		return nil, output
+	}
+	return nil, nil
 }
 
 func preCreateCallback(info handler.HookEvent) error {
-	return hookCallback(hooks.HookPreCreate, info)
+	err, _ := hookCallback(hooks.HookPreCreate, info, false)
+	return err
 }
 
-func preFinishCallback(info handler.HookEvent) error {
-	return hookCallback(hooks.HookPreFinish, info)
+func preFinishCallback(info handler.HookEvent) (error, []byte) {
+	return hookCallback(hooks.HookPreFinish, info, true)
 }
 
 func SetupHookMetrics() {

pkg/handler/config.go

@@ -48,7 +48,7 @@ type Config struct {
 	// PreFinishResponseCallback will be invoked after an upload is completed but before
 	// a response is returned to the client. Error responses from the callback will be passed
 	// back to the client. This can be used to implement post-processing validation.
-	PreFinishResponseCallback func(hook HookEvent) error
+	PreFinishResponseCallback func(hook HookEvent) (error, []byte)
 }
 
 func (config *Config) validate() error {

pkg/handler/unrouted_handler.go

@@ -406,7 +406,7 @@ func (handler *UnroutedHandler) PostFile(w http.ResponseWriter, r *http.Request)
 		// Directly finish the upload if the upload is empty (i.e. has a size of 0).
 		// This statement is in an else-if block to avoid causing duplicate calls
 		// to finishUploadIfComplete if an upload is empty and contains a chunk.
-		if err := handler.finishUploadIfComplete(ctx, upload, info, r); err != nil {
+		if err := handler.finishUploadIfComplete(ctx, upload, info, r, w); err != nil {
 			handler.sendError(w, r, err)
 			return
 		}
@@ -668,13 +668,13 @@ func (handler *UnroutedHandler) writeChunk(ctx context.Context, upload Upload, i
 	handler.Metrics.incBytesReceived(uint64(bytesWritten))
 	info.Offset = newOffset
 
-	return handler.finishUploadIfComplete(ctx, upload, info, r)
+	return handler.finishUploadIfComplete(ctx, upload, info, r, w)
 }
 
 // finishUploadIfComplete checks whether an upload is completed (i.e. upload offset
 // matches upload size) and if so, it will call the data store's FinishUpload
 // function and send the necessary message on the CompleteUpload channel.
-func (handler *UnroutedHandler) finishUploadIfComplete(ctx context.Context, upload Upload, info FileInfo, r *http.Request) error {
+func (handler *UnroutedHandler) finishUploadIfComplete(ctx context.Context, upload Upload, info FileInfo, r *http.Request, w http.ResponseWriter) error {
 	// If the upload is completed, ...
 	if !info.SizeIsDeferred && info.Offset == info.Size {
 		// ... allow custom mechanism to finish and cleanup the upload
@@ -690,9 +690,13 @@ func (handler *UnroutedHandler) finishUploadIfComplete(ctx context.Context, uplo
 		handler.Metrics.incUploadsFinished()
 
 		if handler.config.PreFinishResponseCallback != nil {
-			if err := handler.config.PreFinishResponseCallback(newHookEvent(info, r)); err != nil {
+			err, output := handler.config.PreFinishResponseCallback(newHookEvent(info, r))
+			if err != nil {
 				return err
 			}
+			if output != nil {
+				w.Header().Set("X-pre-finish-response", string(output))
+			}
 		}
 	}