Delete batched callback before executing

[joshestein]

If a callback within batchedCallbacks calls assign we have an infinite loop. Removing the callback from batchedCallbacks before executing it breaks this loop.

Consider a callback calling assign. assign will call batch, which will loop through all batchedCallbacks and execute each one. If one of those callbacks calls assign we will continue indefinitely.

By first removing the callback from batchedCallbacks, then executing we ensure that when the callback calls assign the callback is no longer part of the enqueued batchedCallbacks.

Minimal example with infinite loop:

import { observe } from "@mathigon/boost";

const state = observe<{ count: number }>({ count: 0 });
const model = observe<{ field: string }>({ field: "value" });

model.watch(({ field }) => {
  state.assign({ count: field.length });
});

model.assign({ field: "new value" });