[Bug?]: Plug'n'Play causes Jest to detect open handles with some @types/ packages

[WesCossick]

Self-service

• I'd be willing to implement a fix

Describe the bug

If Plug'n'Play is used, for both Yarn 2 and Yarn 3, Jest will detect open handles inside .pnp.cjs for the @types/express and @types/supertest packages. Here's the message from Jest:

Jest has detected the following 5 open handles potentially keeping Jest from exiting:

  ●  ZLIB

      12326 |           });
      12327 |         } else {
    > 12328 |           const decompressedData = external_zlib_default().inflateRawSync(data);
            |                                                            ^
      12329 |           this.fileSources.set(index, decompressedData);
      12330 |           return decompressedData;
      12331 |         }

      at ZipFS.getFileSource (.pnp.cjs:12328:60)
      at ZipFS.readFileBuffer (.pnp.cjs:12648:17)
      at ZipFS.readFileSync (.pnp.cjs:12634:23)

Other @types/ packages may be affected, though I wasn't able to find any. Most @types/ packages do not appear to be affected by this bug.

To reproduce

Below is the closest I could come to creating a reproduction using the Sherlock Playground. Tests took minutes, not seconds, to run, if they even finished running at all. The editor often froze, sometimes it wouldn't allow me to type, many times the test would fail with no output or indication why, results would differ even without changing the code, I occasionally received errors about React, and finally I started receiving "502: Bad Gateway" errors. It was at this point that I gave up.

Instead, I highly recommend taking a look at the GitHub repository I created to reproduce the error using various versions of Yarn with and without Plug'n'Play enabled: https://github.com/WesCossick/reproduce-zlib-open-handle.

const fs = require('fs');

await packageJsonAndInstall({
  scripts: {
    test: "jest --detectOpenHandles --forceExit 2>&1",
  },
  dependencies: {
    "@types/express": "^4.17.13",
    "@types/jest": "^27.0.1",
    jest: "^27.1.0",
    "ts-jest": "^27.0.5",
    typescript: "~4.2.0",
  },
});

fs.writeFileSync('tsconfig.json', `{
  "include": ["*"],
  "compilerOptions": {
    "esModuleInterop": true,
    "module": "CommonJS",
    "moduleResolution": "Node",
    "strict": true,
    "target": "ES2019"
  }
}`);

fs.writeFileSync('jest.config.js', `module.exports = {
  preset: "ts-jest",
  testEnvironment: "node",
  testFailureExitCode: 0,
};`);

fs.writeFileSync('hello-world.ts', `export default () => "Hello world!";`);

fs.writeFileSync('hello-world.test.ts', `import helloWorld from "./hello-world";
it("Works", () => {
  expect(helloWorld()).toBe("Hello world!");
});`);

await yarn('run', 'test'); // Often the first run doesn't detect open handles
const output = await yarn('run', 'test');

console.log(output);

await expect(output).toContain('1 passed, 1 total');
await expect(output).not.toContain('potentially keeping Jest from exiting');

Environment

System:
OS: macOS 11.5.2
CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Binaries:
Node: 14.17.0 - /private/var/folders/nf/rf7d163x7p3g_jkyzmzx6mv40000gn/T/xfs-9b2da1a6/node
Yarn: 3.0.1 - /private/var/folders/nf/rf7d163x7p3g_jkyzmzx6mv40000gn/T/xfs-9b2da1a6/yarn
npm: 7.20.3 - /usr/local/bin/npm

Additional context

No response

[Psidium]

I'm having this warning with Jest too. In my case it says there are 6 open handles in a test dynamically import()ing the files being tested. I call await import() 6 times and I have 6 open handles.

Something like (Maybe won't reproduce, sometimes it does sometimes it doesn't).

const fs = require('fs');

await packageJsonAndInstall({
  scripts: {
    test: "jest --detectOpenHandles --forceExit 2>&1",
  },
  dependencies: {
    "@types/jest": "^27.0.1",
    jest: "^27.1.0",
    "ts-jest": "^27.0.5",
    typescript: "~4.2.0",
  },
});

fs.writeFileSync('tsconfig.json', `{
  "include": ["*"],
  "compilerOptions": {
    "esModuleInterop": true,
    "module": "CommonJS",
    "moduleResolution": "Node",
    "strict": true,
    "target": "ES2019"
  }
}`);

fs.writeFileSync('jest.config.js', `module.exports = {
  preset: "ts-jest",
  testEnvironment: "node",
  testFailureExitCode: 0,
};`);

fs.writeFileSync('hello-world.ts', `export const helloWorld = () => Promise.resolve("Hello world!");`);
fs.writeFileSync('second-file.ts', `export const second = () => "aa";`);

fs.writeFileSync('hello-world.test.ts', `it("Works", async () => {
  const { helloWorld } = await import("./hello-world");
  const { second } = await import("./second-file");
  expect(second()).toBe("aa");
  expect(helloWorld()).resolves.toEqual("Hello world!");
});`);

await yarn('run', 'test'); // Often the first run doesn't detect open handles
const output = await yarn('run', 'test');

console.log(output);

await expect(output).toContain('1 passed, 1 total');
await expect(output).not.toContain('potentially keeping Jest from exiting');

[merceyz]

This was an issue in Jest which was tracked in jestjs/jest#11542 and fixed in jestjs/jest#12022