mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-26 06:34:20 +08:00
Chris Tate
f7ad1f96a4
The ESNext array lib is now part of the type world, and Array.fromAsync(source, mapFn?) compiles when the source is an array of values or of promises. Each call lowers to an async helper with the spec's loop: elements are awaited through the async-from-sync iterator, with the same microtask turns as a `for await` loop over an array, and a mapping function's result is awaited before it is stored. A throwing or rejecting mapping function and a rejected element close the iterator before the returned promise rejects, on the turn Node rejects it. Async generator sources, a thisArg, and arrays that mix values and promises are refused.
57 lines
2.2 KiB
TypeScript
57 lines
2.2 KiB
TypeScript
// Array.fromAsync over arrays of values and of promises, with and without a
|
|
// mapping function, interleaved with other promise jobs: every result,
|
|
// rejection and iterator close lands on the microtask Node uses. Node.js prints
|
|
// the same.
|
|
const log: string[] = [];
|
|
async function ticker(n: number): Promise<void> {
|
|
for (let i = 0; i < n; i++) {
|
|
log.push("t" + i);
|
|
await null;
|
|
}
|
|
}
|
|
function report(label: string, job: Promise<number[]>): Promise<number> {
|
|
return job.then(
|
|
(a) => log.push(label + " " + a.join(",")),
|
|
(e) => log.push(label + " caught " + (e as Error).message),
|
|
);
|
|
}
|
|
async function main(): Promise<void> {
|
|
const tick = ticker(24);
|
|
const jobs = [
|
|
report("values", Array.fromAsync([1, 2, 3])),
|
|
report("promises", Array.fromAsync([Promise.resolve(4), Promise.resolve(5)])),
|
|
report("empty", Array.fromAsync([] as number[])),
|
|
report("map", Array.fromAsync([1, 2], (x: number, i: number) => x * 2 + i)),
|
|
report("async map", Array.fromAsync([1, 2], async (x: number) => x + 1)),
|
|
report("promise map", Array.fromAsync([3, 4], (x: number) => Promise.resolve(x * x))),
|
|
report("promises async map", Array.fromAsync([Promise.resolve(1), Promise.resolve(2)], async (x: number) => x * 5)),
|
|
report(
|
|
"map throws",
|
|
Array.fromAsync([1, 2], (x: number) => {
|
|
if (x === 2) throw new Error("map failed");
|
|
return x;
|
|
}),
|
|
),
|
|
report(
|
|
"async map rejects",
|
|
Array.fromAsync([1, 2, 3], async (x: number) => {
|
|
if (x === 2) throw new Error("async map failed");
|
|
return x;
|
|
}),
|
|
),
|
|
report("first rejected", Array.fromAsync([Promise.reject(new Error("first")), Promise.resolve(1)])),
|
|
report("second rejected", Array.fromAsync([Promise.resolve(1), Promise.reject(new Error("second"))])),
|
|
report(
|
|
"later",
|
|
Array.fromAsync([new Promise<number>((resolve) => setTimeout(() => resolve(7), 1)), Promise.resolve(8)]),
|
|
),
|
|
];
|
|
log.push("sync end");
|
|
await Promise.all(jobs);
|
|
await tick;
|
|
console.log(log.join("\n"));
|
|
const strings = await Array.fromAsync(["a", "b"], async (s: string, i: number) => s.repeat(i + 1));
|
|
console.log(strings.join("|"), strings.length);
|
|
}
|
|
main();
|