AsyncBatcher: Tracking in flight batches

[shidel-dev]

I was hopeful that I could do the following:

Server State -> apply idle + pending batches client side -> optimistic state. Then once batches commit have a new Base Server State (plus any new idle actions that happened during the save).

this is conceptually nice as any changes that happen during a ongoing save are not trampled by the new server state from a previous commit.

However I noticed that AsyncBatcher just clears it's items before doing the execute. To me this seems like a weird choice, as those pending batches are kind of lost as far as the state subscriptions go. As far as I could tell it only records a count for how many are currently executing.

here is the code in question:

pacer/packages/pacer/src/async-batcher.ts

Lines 384 to 403 in a894009

	const batch = this.peekAllItems() // copy of the items to be processed (to prevent race conditions)
	this.clear() // Clear items before processing to prevent race conditions
	this.options.onItemsChange?.(this)
	this.#setState({ isExecuting: true, executeCount: currentExecuteCount })
	try {
	const currentAsyncRetryer = new AsyncRetryer(
	this.fn,
	this.options.asyncRetryerOptions,
	)
	this.asyncRetryers.set(currentExecuteCount, currentAsyncRetryer)
	const result = await currentAsyncRetryer.execute(batch) // EXECUTE
	this.#setState({
	totalItemsProcessed:
	this.store.state.totalItemsProcessed + batch.length,
	lastResult: result,
	successCount: this.store.state.successCount + 1,
	})
	this.options.onSuccess?.(result, batch, this)

Between the call to clear, and the call to onSuccess the state for the inflight items is lost, thus requiring anyone who wants to purely derive the optimistic state from the idle + inflight actions to have to do their own book keeping.

I believe that logically there should be state which captures the inflight items that can be subscribed to.