fetch() showing "a promise was created in a handler but was not returned from it" warning

I am getting this warning:

a promise was created in a  handler but was not returned from it

For this code:

return new Promise((resolve, reject) => {
    return fetch(`${BASEURL}test/`)
    .then((response) => response.json())
    .then(resolve)
    .catch(reject);
});

Looking over the bluebird docs, I don’t understand why I’m getting this warning. My promise handler definitely returns a value. So why the warning?

P.S. You also have a double space in your warning message before the word ‘handler’.

[whizkid77]

For others who run into this issue (and are pretty sure they are returning from all handlers)

I am encountering same warning when wrapping Promise.resolve(fetch(…)). I cannot reproduce warning in isolation though. In majority of cases, it works just fine. The warning occurs when two fetch requests are being issued in quick succession. Putting second invocation of wrapped fetch into setTimeout clause avoids the warning. The warning seems to be emitted due to some racecondition, however I do not know enough bluebird internals to actually debug it…

Thanks @jesenko. I ran into the same issue where two fetch() calls are run in quick succession. Wrapping in setTimeout avoids the warning as well. I am using React Native’s fetch() polyfill.

I’d suggest reopening this issue…

[jonesnc]

I’m getting this warning when using RxJS’s flatMap operator, but only in flatMap observers that are chained after the first flatMap observer is executed.

http://stackoverflow.com/questions/34728324/how-do-i-get-rid-of-a-bluebird-warning-when-chaining-more-than-one-flatmap-opera