@strapi/data-transfer/dist/utils/writable-async-write.mjs

Data transfer capabilities for Strapi

import { once } from 'node:events';
import { finished } from 'node:stream/promises';

/**
 * Async helper for application code that `await`s sequential writes to a `Writable`.
 *
 * 1. Waits until `writable.write` invokes its callback (chunk accepted / `_write` finished).
 * 2. If `write()` returned `false` **and** `writable.writableNeedDrain` is still true after the
 *    callback, waits for `'drain'`.
 *
 * We check both: the return value tells us backpressure was signaled; `writableNeedDrain` avoids
 * awaiting `'drain'` when it already fired before we subscribed (would otherwise hang forever).
 *
 * While waiting for `'drain'`, we also race {@link finished} so destroying the writable (e.g. abort)
 * cannot leave this promise pending forever.
 */ async function write(writable, chunk) {
    let flushed = true;
    await new Promise((resolve, reject)=>{
        let settled = false;
        const finish = (fn)=>{
            if (settled) {
                return;
            }
            settled = true;
            writable.off('error', onError);
            fn();
        };
        const onError = (err)=>{
            finish(()=>reject(err));
        };
        writable.once('error', onError);
        flushed = writable.write(chunk, (err)=>{
            if (err) {
                // Do not reject or remove `error` here: Node may emit `error` after this callback, and
                // clearing the listener first would leave that emission unhandled.
                setImmediate(()=>{
                    if (!settled) {
                        finish(()=>reject(err));
                    }
                });
                return;
            }
            finish(()=>resolve());
        });
    });
    if (!flushed && writable.writableNeedDrain) {
        // Without `finished`, awaiting only `drain` can hang forever if the writable is destroyed first.
        await Promise.race([
            once(writable, 'drain'),
            finished(writable, {
                readable: false,
                writable: true
            })
        ]);
    }
}

export { write };
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