Unable to delete things from global.

[gdborton]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
delete global.someProp doesn't work.

If the current behavior is a bug, please provide the steps to reproduce and either a repl.it demo through https://repl.it/languages/jest or a minimal repository on GitHub that we can yarn install and yarn test.

Repl.it - https://repl.it/GXd3

const assert = require('assert');

describe('removing stuff from the global object', () => {
  describe(`via 'delete global.prop'`, () => {
    it('should set the value to undefined', () => {
      global.someValue = 'asdf';
      assert.equal(global.someValue, 'asdf');
      delete global.someValue;
      assert.equal(global.someValue, undefined);
    });
  });

  describe(`via 'global.prop = undefined;'`, () => {
    it('should set the value to undefined', () => {
      global.someValue2 = 'asdf';
      assert.equal(global.someValue2, 'asdf');
      global.someValue2 = undefined;
      assert.equal(global.someValue2, undefined);
    });
  });
});

What is the expected behavior?
delete global.someProp should make global.someProp === undefined true.

This works in mocha, jasmine, plain old node, and I think it works when running via vm. We're investigating a move to Jest, but are running into some subtle issues related to this.

For example this function in enzyme doesn't behave correctly - https://github.com/airbnb/enzyme/blob/master/src/Utils.js#L213

We could attempt to work around this, but I feel like this will repeatedly come up in our codebase and will lead to lots of wasted time.

Please provide your exact Jest configuration and mention your Jest, node, yarn/npm version and operating system.
node - v4.6.2
npm - 2.15.11
jest - v19.0.0
os - OSX Sierra v10.12.1

[rogeliog]

Hi! Thanks for reporting this

I think it has to do with vm, which is what Jest uses for the environment https://github.com/facebook/jest/blob/master/packages/jest-environment-node/src/index.js

This is what I get when running it in a Node repl

[aaronabramov]

looks like it has been fixed here nodejs/node#11266

[aaronabramov]

yeah. i can confirm that it works on node 7.7.3

dabramov-mbp ~ node -v
v7.7.3
dabramov-mbp ~ node
> const sb = {a: 1, b: 2, c: 3}
undefined
> vm.createContext(sb)
{ a: 1, b: 2, c: 3 }
> vm.runInContext('delete this.a;', sb)
true
> sb
{ b: 2, c: 3 }

[gdborton]

Ooph, so we'll have to update node to get around this?

[aaronabramov]

@gdborton that would be the easiest!

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