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// copied from
// https://github.com/algolia/autocomplete.js/blob/307a7acc4283e10a19cb7d067f04f1bea79dc56f/packages/autocomplete-core/src/utils/createConcurrentSafePromise.ts#L1:L1
/**
* Creates a runner that executes promises in a concurrent-safe way.
*
* This is useful to prevent older promises to resolve after a newer promise,
* otherwise resulting in stale resolved values.
*/
export function createConcurrentSafePromise() {
let basePromiseId = -1;
let latestResolvedId = -1;
let latestResolvedValue = undefined;
return function runConcurrentSafePromise(promise) {
basePromiseId++;
const currentPromiseId = basePromiseId;
return Promise.resolve(promise).then((x) => {
// The promise might take too long to resolve and get outdated. This would
// result in resolving stale values.
// When this happens, we ignore the promise value and return the one
// coming from the latest resolved value.
//
// +----------------------------------+
// | 100ms |
// | run(1) +---> R1 |
// | 300ms |
// | run(2) +-------------> R2 (SKIP) |
// | 200ms |
// | run(3) +--------> R3 |
// +----------------------------------+
if (latestResolvedValue && currentPromiseId < latestResolvedId) {
return latestResolvedValue;
}
latestResolvedId = currentPromiseId;
latestResolvedValue = x;
return x;
});
};
}
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