sts.assumeRole().promise() returns undefined when succeds

[mim-Armand]

Using callback works in both happy-path and failure:

// This works
assumeRole() {
    let params = {
        RoleArn: 'arn:aws:iam::xxxxxx:role/test_assume_role',
        RoleSessionName: 'Bob',
    };
    return sts.assumeRole(params, function(err, data) {
        if (err) console.log(err, err.stack); // an error occurred
        else     console.log(data);           // successful response
    });
  }

using .promise() however returns undefined when the request succeeds, it behaves as expected when the request fails:

// This returns undefined for happy-path
assumeRole() {
    let params = {
        RoleArn: 'arn:aws:iam::xxxxxx:role/test_assume_role',
        RoleSessionName: 'Bob',
    };
    
    return sts.assumeRole(params)
      .promise()
      .then((data) => {
        console.log('ASSUME ROLE RESULTS >>> ', data);
      })
        .catch( (err) => {
          console.log('ERROR ASSUMING ROLE: ', err);
        });
  }

Thanks

[AllanZhengYP]

Hi @mim-Armand, I cannot reproduce this issue. Are you using any un-default promise library?

[mim-Armand]

Not using any library for that, I simply add ( the undocumented ) .promise() at the end of the method call, as it does promisify most of the other methods I've worked with, it does with this one too, the only difference is that it returns undefined when the promise is resolved.

So sts.assumeRole(params).promise() returns the correct response for you? If so, please let me know and I'll do more investigation to find out what was the cause of the issue. thanks

[AllanZhengYP]

Yes. I used the code snippet you shared as above and it works as expected. I was using a test user with all STS permissions. Can you show me what's the printout you get from the code snippet above?

[mim-Armand]

the printout was undefined when stringified, but I think found the problem, adding .promise() doesn't return a normal promise, in contrary to the promises standard api which can have more than one .then() and executes them one after the other, AWS Node SDK, executes the second then() as well but it doesn't pass the resolved value to thens after the first one.
I had one then() in my class and one in my test, I was logging the results in my test which was printing undefined. however, logging the results in the class itself works, and if I remove the then() from the class, the test will start working.
So I will close this issue as it's kind of solved, I appreciate your help @AllanFly120

[realtaraharris]

I have run into this same issue, and the discussion above is about as clear as mud. Is there an actual code example demonstrating how to work around this issue?

I can't just use the v3 SDK because it won't be out for at least another six months...

[mim-Armand]

@maxharris9 The snippet in the original post actually works, just make sure to consume the promise only in one place otherwise it may cause a racing condition.

There is a difference ( or maybe a bug ) in the implementation of the Promise in this SDK ( at least the version I was using back then ) and the standard implementation/specifications of the Promise APIs:
In the standard spec, when a promise is resolved/rejected, all the subscribers will be notified ( This is called Promise Branching ), but here only one of them will receive the results ( that's not the case however when the promise is rejected, pointing to a possible bug, again )

I will re-open this issue hoping someone will explain it better and/or clearer than me to help you out, or put it on the roadmap if it's a bug or something that can help more people, but otherwise please feel free to close it

[realtaraharris]

Dear Amazon: await sts.assumeRole(params).promise() doesn't work, and it should

[AllanZhengYP]

@maxharris9 Can you make sure the 'complete' event is triggered in your request? like here:

request.
  on('complete', function(resp) {
    console.log('request completes: ', resp.data);
  });
await request.promise();

More information about event listeners: https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/using-a-response-event-handler.html

[no-response]

This issue has been automatically closed because there has been no response to our request for more information from the original author. With only the information that is currently in the issue, we don't have enough information to take action. Please reach out if you have or find the answers we need so that we can investigate further.

[lock]

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