No error message in case of failure during save page

Manuel Leduc the auto-save has code to indicate when the save fails and the content remains dirty, but the problem is that the storage component doesn't throw an exception when the save fails . The storage uses fetch to make the save HTTP request but doesn't check the response and fetch itself doesn't throw an exception. From https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API

It returns a Promise that resolves to the Response to that request — as soon as the server responds with headers — even if the server response is an HTTP error status.

It's up to the code calling fetch to check the response and throw an exception if there is a problem (i.e. it's up to the code calling fetch to define what a failed request is).