Class DeckDiscussionListState

Get the parameters that should be passed in the API request. Do not include page offset unless subclass overrides loadPage.

Reconcile the realtime additions after a background revalidation.

refresh() empties extraDiscussions, because it routes through clear(). revalidate() deliberately does not clear anything before it asks the API, so it rebuilds pages and leaves extraDiscussions alone — and the first page it gets back contains exactly the discussions realtime put there, since a new post is what moved them to the top. Left unhandled they render from both places at once, which is what a reader coming back to an idle tab sees as a duplicate.

Only the ids the new pages actually contain are dropped. A revalidation that failed resolves rather than rejecting and leaves pages untouched, so clearing unconditionally would take realtime's additions off a list that was never reloaded.