lolex.install({target: otherContext}) injects properties from original global

[fatso83]

• Lolex version : 5.1.1
• Environment : Chrome

What did you expect to happen? That lolex.install({target: myContext, ...otherProps}) would basically work like lolex.withGlobal(target).install({...otherProps}).

What actually happens If your environment supports performance and you do lolex.install({target: { toFake: ['setTimeout'] } }) it still fakes and injects performance into the returned clock.

assert.isUndefined(clock.performance);

Will therefore fail. This happens because the checks on whether to add the prop references the prop that was set using the default lolex instance.

How to reproduce

function noop(){}
global.performance = {now:function(){}};
var lolex = require('./src/lolex-src');
var clock2 = lolex.install({target: {Date: noop}});
assert.isUndefined(clock2.performance); // fails

[fatso83]

An easy fix would be to either disallow the target prop and explicitly say "Update your code to uselolex.withGlobal(target).install(config)"` or just do it under the covers in the install method:

if(config.target) {
   var target = config.target;
   delete config.target;
   return withGlobal(target)(config);
}

[SimenB]

What if I want to install fake versions of timers from one thing into some other object? Is that a valid use case?

[fatso83]

@SimenB I can't really come up with any reason to do that ... but I guess someone might want that ... for some unknown reason?

const myTarget = { Date: sinon.fake() };
lolex.withGlobal(global.jsDomWindow).install({target: myTarget});

That would install fake performance timers into myTarget, so you could tamper with that object without worrying about messing too much with global.jsDomWindow. Not sure who would need such a use case, but we can keep it. Then we would need to document it, with a hint to why you would use it.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[SimenB]

I'm down with throwing on target usage and directing to use the factory function for that use case. It works with any use case I can think of at least

[fatso83]

318

[SimenB]

This is fixed now, right?