doc: further fix async iterator example

ronag · codebytere · commit 729b96137e57 · 2020-02-17T11:17:34.000-08:00
Further fixes an issue with the async iterator example where an incorrect assumption was made in regards that drain or error is always invoked after !write(). Fixes: #31365 PR-URL: #31367 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
diff --git a/doc/api/stream.md b/doc/api/stream.md
@@ -2644,12 +2644,22 @@ const finished = util.promisify(stream.finished);
 
 const writable = fs.createWriteStream('./file');
 
+function drain(writable) {
+ if (writable.destroyed) {
+ return Promise.reject(new Error('premature close'));
+ }
+ return Promise.race([
+ once(writable, 'drain'),
+ once(writable, 'close')
+ .then(() => Promise.reject(new Error('premature close')))
+ ]);
+}
+
 async function pump(iterable, writable) {
 for await (const chunk of iterable) {
 // Handle backpressure on write().
 if (!writable.write(chunk)) {
- if (writable.destroyed) return;
- await once(writable, 'drain');
+ await drain(writable);
 }
 }
 writable.end();

-Original file line number
+Diff line change
 constwritable=fs.createWriteStream('./file');
 +functiondrain(writable) {
 +if (writable.destroyed) {
 +returnPromise.reject(newError('premature close'));
 + }
 +returnPromise.race([
 +once(writable, 'drain'),
 +once(writable, 'close')
 + .then(() =>Promise.reject(newError('premature close')))
 + ]);
 +}
++
 asyncfunctionpump(iterable, writable) {
 forawait (constchunkofiterable) {
 // Handle backpressure on write().
 if (!writable.write(chunk)) {
 -if (writable.destroyed) return;
 -awaitonce(writable, 'drain');
 +awaitdrain(writable);
+ }
+ }
 writable.end();