fix(jest-runtime): Guard '_isMockFunction' access with 'in'

[rbuckton]

Summary

This fixes an issue in jest-runtime when attempting to reset global mocks. When jest is running inside of VS Code to test a VS Code extension, it attempts to read _isMockFunction from a Proxy that happens to throw in its get handler when you unconditionally read a property that does not exist. Prefixing this condition with a test for in avoids evaluating the get hook.

NOTE: While this does resolve this specific case, it's still possible a global could be a Proxy that even throws on in, though that would generally be a bad practice. It would be much safer to replace _isMockFunction entirely with a WeakSet that does not interact with a Proxy at all, but that is a far more comprehensive change than I'm willing to commit to at this point.

Test plan

I've tested this locally through the use of a custom JestEnvironment, such as this one:

import NodeEnvironment from "jest-environment-node";
export default class extends NodeEnvironment {
  async setup() {
    await super.setup();
    this.global.UNSAFE_GLOBAL = new Proxy({}, {
      get(target, p, receiver) {
        if (p === "_isMockFunction") throw new Error();
      }
    });
  }
  async teardown() {
    this.global.UNSAFE_GLOBAL = null;
    await super.teardown();
  }
}

I've added something similar to the above as a test in this PR.

Fixes #14095

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: rbuckton / name: Ron Buckton (5485abd)
• ✅ login: SimenB / name: Simen Bekkhus (7239e0f, 0446565, 92cfa13)

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[SimenB]

clean fix, thanks!

I'd be interested in the WeakSet change you mention if you ever find the time! 😀

[SimenB]

https://github.com/jestjs/jest/releases/tag/v29.6.0

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