Clear a stale Last-Event-ID header when the event ID is reset - #13140

Delete Last-Event-ID from the reused EventSource request when the last event ID string is empty. Add the Fetch header-list delete reference used by the new step.

After one reconnect has set this header, a later empty id field resets the EventSource state but currently leaves the old header on the saved request. A subsequent reconnect can therefore send the stale value, contrary to the reset example in this section.

Suggested regression coverage: receive id: 1, reconnect, receive an empty id field, then verify the next request omits Last-Event-ID.

Spec: https://html.spec.whatwg.org/multipage/server-sent-events.html#reestablish-the-connection

• At least two implementers are interested (and none opposed):
  • …
  • …
• Tests are written and can be reviewed and commented upon at:
  • …
• Implementation bugs are filed:
  • Chromium: …
  • Gecko: …
  • WebKit: …
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): …
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• Corresponding HTML AAM & ARIA in HTML issues & PRs:
• MDN issue is filed: …
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

/infrastructure.html ( diff )
/server-sent-events.html ( diff )