Danny Kim
34 lines
1.3 KiB
TypeScript
34 lines
1.3 KiB
TypeScript
// What the child process call sites share: the exit status, read right after
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// `spawn` so the exit event cannot pass unseen while the caller reads the
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// streams, and echoing output without outrunning a slow reader.
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import type { ChildProcess } from "node:child_process";
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import { once } from "node:events";
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import { constants } from "node:os";
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import type { Writable } from "node:stream";
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// Resolves once the process exits, before its streams close, with its exit
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// code, or with 128 plus the signal number if a signal killed it, as a shell
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// reports. A process that fails to start rejects with the spawn error.
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export function exitCode(child: ChildProcess): Promise<number> {
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const code = new Promise<number>((resolve, reject) => {
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child.once("error", reject);
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child.once("exit", (exit, signal) => {
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resolve(exit ?? (signal === null ? 1 : 128 + constants.signals[signal]));
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});
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});
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// Callers await it after draining the streams; a failed start must not be
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// reported as an unhandled rejection before then.
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code.catch(() => {});
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return code;
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}
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// Writes a chunk, waiting for the stream to drain when its buffer is full.
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export async function echo(
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stream: Writable,
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chunk: string | Uint8Array,
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): Promise<void> {
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if (!stream.write(chunk)) {
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await once(stream, "drain");
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}
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}
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