How to dispose a ReadStream passed to body option correctly - Jest JSSTREAM open handle warning

[Rychu-Pawel]

I'm getting Jest warning when executing one of my tests that it detected an open handle:

Jest has detected the following 1 open handle potentially keeping Jest from exiting:

  ●  JSSTREAM

      3 | import { constants as fsConsts } from 'fs';
    > 4 | import got from 'got';

      at Object.<anonymous> (node_modules/http2-wrapper/source/utils/js-stream-socket.js:6:25)
      at Object.<anonymous> (node_modules/http2-wrapper/source/proxies/h1-over-h2.js:5:24)
      at Object.<anonymous> (node_modules/http2-wrapper/source/index.js:13:5)
      at Object.<anonymous> (node_modules/got/dist/source/core/options.js:11:1)
      at Object.<anonymous> (node_modules/got/dist/source/core/index.js:19:1)
      at Object.<anonymous> (node_modules/got/dist/source/as-promise/index.js:5:1)
      at Object.<anonymous> (node_modules/got/dist/source/create.js:2:1)
      at Object.<anonymous> (node_modules/got/dist/source/index.js:1:1)
      [...]

I'm wondering if I'm disposing the stream correctly and this is just a false alarm or should I do something more? The test and my app exit correctly. This is a simplified example what my code looks like:

let fileHandle: fs.FileHandle | null = null;
let fileStream: ReadStream | null = null;

try {
  fileHandle = await fs.open(this.fullFilePath, fsConsts.O_RDONLY);

  fileStream = fileHandle.createReadStream({
                start: this.chunkStartPosition,
                end: this.chunkStartPosition + this.chunkLengthInBytes - 1
            });

  this.ongoingRequestPromise = gotInstance.post(this.uploadUrl, { body: fileStream });

  await this.ongoingRequestPromise;
}
finally {
  fileStream?.close();
  fileStream?.destroy();
  fileHandle?.close();
}

[sindresorhus]

the JSSTREAM warning is actually a false positive from Jest's --detectOpenHandles - its related to http2-wrapper's global connection pool, not your file stream (see issue #2288).

your cleanup code looks correct. got will destroy the stream when the request completes. just make sure to await the request before closing the fileHandle:

try {
  const fileStream = fileHandle.createReadStream({
    start: this.chunkStartPosition,
    end: this.chunkStartPosition + this.chunkLengthInBytes - 1
  });
  
  await gotInstance.post(this.uploadUrl, { body: fileStream });
} finally {
  await fileHandle?.close(); // await this
}

to fix the Jest warning, either:

1. remove the --detectOpenHandles flag
2. set http2: false in your got instance if you dont need HTTP/2:

const gotInstance = got.extend({
  http2: false
});

the warning dosen't indicate a real leak - your streams are being cleaned up properly.