Inconsistency in `toHaveBeenCalledExactlyOnceWith` for `undefined` values

[DesselBane]

The toHaveBeenCalledExactlyOnceWith differentiates between a call where an argument with the value of undefined is passed and a call where nothing is passed. Technically this is a difference in JS but I would argue not a meaningfull one.

  it('should not make a difference', () => {
    const foo = {
      bar: (needed: string, maybe?: string) => {},
    }

    const barSpy = vi.spyOn(foo, 'bar')

    foo.bar('something')
    
    // Works
    expect(barSpy).toHaveBeenCalledExactlyOnceWith('something')

    barSpy.mockReset()

    const someArgument = undefined

    foo.bar('something', someArgument)

    // Works
    expect(barSpy).toHaveBeenCalledExactlyOnceWith('something', undefined)

   // Fails
    expect(barSpy).toHaveBeenCalledExactlyOnceWith('something')
  })

I would expect the matcher to pass in all 3 scenarios.

[keeganwitt]

What environment were you testing this in? I see the behavior you mention when using the playground, but I don't see that behavior when running in a local test. I'm not sure why. I don't know much about sandpack.

[DesselBane]

Hm interresting. I run it in vite (maybe that has something to do with it).