nock.recorder.rec does not record when stream not put into flowing mode

[att14]

What is the expected behavior?
nock.recorder.play() should contain the recorded version of the request to GetObject.

What is the actual behavior?
Request does not appear in array returned from nock.recorder.play().

How to reproduce the issue

const nock = require('nock');
const { S3Client, GetObjectCommand } = require('@aws-sdk/client-s3');

const s3 = new S3Client();
const bucket = '';
const key = '';

async function main() {
  nock.recorder.rec({ dont_print: true });

  try {
    await s3.send(new GetObjectCommand({ Bucket: bucket, Key: 'invalid' }));
  } catch { }

  const response = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
  console.log(response.Body.statusCode);

  console.log(nock.recorder.play());
}

main()
  .then(() => process.exit(0))
  .catch((err) => {
      console.log(err);
      process.exit(1);
  })

Fill in bucket and key and run. key must be a valid and present S3 key.

With a valid bucket and key the output is:

200
[
  '\n' +
    `nock('https://test-onelivex.s3.us-east-2.amazonaws.com:443', {"encodedQueryParams":true})\n` +
    "  .get('/invalid')\n" +
    '  .query({"x-id":"GetObject"})\n' +
    '  .reply(404, "<?xml version=\\"1.0\\" encoding=\\"UTF-8\\"?>\\n<Error><Code>NoSuchKey</Code><Message>The specified key does not exist.</Message><Key>invalid</Key><RequestId>6XB4DKCEPRQPWWY0</RequestId><HostId>pHwvM3hwyAKmDqYq6z6uBRIFos+UhBwM9hMAdOBbuTSXUaM3seP1yTV0C93o3RKE152McDWBnvE=</HostId></Error>", [\n' +
    "  'x-amz-request-id',\n" +
    "  '6XB4DKCEPRQPWWY0',\n" +
    "  'x-amz-id-2',\n" +
    "  'pHwvM3hwyAKmDqYq6z6uBRIFos+UhBwM9hMAdOBbuTSXUaM3seP1yTV0C93o3RKE152McDWBnvE=',\n" +
    "  'Content-Type',\n" +
    "  'application/xml',\n" +
    "  'Transfer-Encoding',\n" +
    "  'chunked',\n" +
    "  'Date',\n" +
    "  'Mon, 19 Apr 2021 00:48:04 GMT',\n" +
    "  'Server',\n" +
    "  'AmazonS3'\n" +
    ']);'
]

Versions

Software	Version(s)
Nock	0.21.1
@aws-sdk/client-s3	3.13.0
Node	v15.12.0

[paulmelnikow]

Hi! Just wagering a guess that this is not a problem with nock. I’d guess an invalid bucket and key is erroring out in the AWS SDK before the HTTP request is made. Maybe you can catch the exception and see.

[att14]

You can see the response is 200 when logged by console.log(response.Body.statusCode). It is the first line of the output.

[att14]

@paulmelnikow thanks for your extremely fast response earlier. I have been looking into this some more and found that adding res.on('data', (chunk) => {}); within the callback of overridenRequest resolves the problem. The reason I did this we because the res.once('end', ...) event was never being hit, so I started seeing which events were and noticed that anytime I added data it would actually record the request. Looking into readable streams I noticed this in the documentation:

If a Readable is switched into flowing mode and there are no consumers available to handle the data, that data will be lost. This can occur, for instance, when the readable.resume() method is called without a listener attached to the 'data' event, or when a 'data' event handler is removed from the stream.

All Readable streams begin in paused mode but can be switched to flowing mode in one of the following ways:

• Adding a 'data' event handler.
• Calling the stream.resume() method.
• Calling the stream.pipe() method to send the data to a Writable.

I guess in this case the stream is never put into flowing mode, so unless the client actually consumes the stream nock won't record anything.

[gr2m]

@att14 could you start a pull request with a test replicating the issue? That'd be a great start to address it

[att14]

Okay, #2257 has been created.