Steps to reproduce: (not needed with attached test project)
create new FlowUI project
add REST API addon from marketplace
add a upload field (doesn’t matter which one) to the UserDetailView
inject it into the controller and add a FileUploadSucceededListener
listener is never called.
As a counter check remove the REST API addon
listener is correctly called upon file upload
This bug drove me nuts already. Some insight I got already: With the REST API the upload request is missing the parts. See also com.vaadin.flow.server.communication.StreamReceiverHandler#doHandleMultipartFileUpload
The hasParts(request) is true when it is working, but false when it isn’t.
I’m guessing there is some faulty filter added by the REST addon.