What you were expecting:
Expected to work as stated in the documentation

The onSuccess function receives the response from the dataProvider call (dataProvider.create() or dataProvider.update()), which is the created/edited record (see the dataProvider documentation for details)

What happened instead:
Instead, onSuccess is called immediately after Save action , and the data parameter is empty

Steps to reproduce:
Copy the code from the documentation and apply

https://codesandbox.io/s/proud-water-10dbo?file=/src/posts/PostEdit.js
after adding code from documentation codeandbox hangs on save

• React-admin version:3.11.4