Bug 215771 – Unhandled Promise Rejection: Abort Error: Fetch is aborted

• Status: RESOLVED
• Resolution: CONFIGURATION CHANGED
• Component: New Bugs

Lots of `Unhandled Promise Rejection: Abort Error: Fetch is aborted` error is being displayed in console, when network is disconnected while data from `ReadableStream` is being read.

The sample code below will abort stream data reading after 1 second.
Chrome browser does not throw an error and ends stream reading gracefully, however Safari and WkWebView threw lots of error in console.

--
```
const url = 'https://...'; // URL which takes more than 1 second to download
function test(url) {
  const abortController = new AbortController();
  window.setTimeout(() => {
    abortController.abort();
  }, 1000);
  window.fetch(url, { signal: abortController.signal }).then(response => {
    const reader = response.body.getReader();
    reader.read().then(function processData({ value, done}) {
      if (done) {
        return;
      }
      return reader.read().then(processData);
    })
    .catch(error => console.error('reader error handled gracefully', error));
  });
}

test(url);
```

This line of the code seems throwing those errors.
https://github.com/WebKit/webkit/blob/950143da027e80924b4bb86defa8a3f21fd3fb1e/Source/WebCore/Modules/streams/ReadableStreamInternals.js#L302

I guess there are lots of internal requests being queued to buffer incoming data for efficient reading. Those requests being cancelled should not be revealed to consumer in console pane.

[youenn fablet]

Right, we should add @promiseFlagsIsHandled to the promises.
In general, we should update the ReadableStream implementation up to spec.

[Radar WebKit Bug Importer]

<rdar://problem/68082772>

[Asheem]

This is a problem in Mapbox-GL-JS that is being faced by a number of users of the library. Reference: https://github.com/mapbox/mapbox-gl-js/issues/8480

Whether using a nested promise or a chained promise, this error is logged to the console when a fetch request is cancelled while reading the response data. 

Link to the code in question: https://github.com/mapbox/mapbox-gl-js/blob/0102e52123fc66df98853620ced6e0e3195fa9a4/src/util/ajax.js#L144-L157

This problem affects our customers who are using logged errors for production applications, and have to handle a large number of these spurious errors.

[Anna]

Any update on this? I opened a new ticket to bump up this issue as it seems to be a continued problem: https://bugs.webkit.org/show_bug.cgi?id=249784 Thanks!

[Alexey Proskuryakov]

*** Bug 249784 has been marked as a duplicate of this bug. ***

[youenn fablet]

I cannot reproduce with the snippet, closing as configuration changed.
I'll fix https://bugs.webkit.org/show_bug.cgi?id=251463 which is still an issue.