sguiheux
Do not abort the connection on authentication errors
At line 218 of eventsource.js you check for error code ≥ 500 and retry the connection:
https://github.com/sguiheux/EventSource/blob/1859fa4ccb8c16e07b09dc458e035ca68e18b8b7/eventsource.js#L218
Errors in the 400 range, on the other hand, will lead to an abort: https://github.com/sguiheux/EventSource/blob/1859fa4ccb8c16e07b09dc458e035ca68e18b8b7/eventsource.js#L306-L318
Retrying the connection on errors that are not internal server errors would favor our use case (where we update authentication headers when they become invalid).
I see two possible options: always retry on errors ≥ 400 (instead of 500), or add a return value to the onError callback and retry if the error handler allows this (this is probably over-engineering?).
It's normal to retry on error >= 500 because it's a server error, so we retry until it works With error < 500, the problem come from the client, so you can retry any time it will not work (404 will be alway 404), so no retry on error < 500.
If your problem is about loosing lastEventID maybe we can add it on onErrorEvent and accept it on EventSource constructor or update function
