Function transactionSink

packages/deno/test/deno-http.test.ts:27–55

* `beforeSendTransaction` hook plus a `waitFor(predicate)` helper * resolves when a matching transaction arrives (or has already arrived)

()

 * resolves when a matching transaction arrives (or has already arrived)
 */
function transactionSink(): {
  transactions: TransactionEvent[];
  beforeSendTransaction: (event: TransactionEvent) => null;
  waitFor: (predicate: (event: TransactionEvent) => boolean) => Promise<TransactionEvent>;
} {
  const transactions: TransactionEvent[] = [];
  const waiters: { predicate: (e: TransactionEvent) => boolean; resolve: (e: TransactionEvent) => void }[] = [];
  return {
    transactions,
    beforeSendTransaction(event) {
      transactions.push(event);
      for (let i = waiters.length - 1; i >= 0; i--) {
        const w = waiters[i]!;
        if (w.predicate(event)) {
          waiters.splice(i, 1);
          w.resolve(event);
        }
      }
      return null;
    },
    waitFor(predicate) {
      const already = transactions.find(predicate);
      if (already) return Promise.resolve(already);
      return new Promise<TransactionEvent>(resolve => {
        waiters.push({ predicate, resolve });
      });
    },
  };
}

// Bind a promise so a real "never arrives" bug fails the test.
function withTimeout<T>(p: Promise<T>, ms: number, what: string): Promise<T> {