Fix #867: Walk properties only once

[mantoni]

This fixes createStubInstance for prototype chains with overrides as reported in #867. One could argue that the fix belongs into the iterator function in sinon.stub. I tried adding a check for whether a property is already stubbed and that also does the trick, but it seemed a bit messy.

Thoughts?

[fatso83]

Good work, I think this looks pretty clean. Just to see if I understand you correctly; the alternative would be to create an analog of your seen object in this part of sinon.stub, right? In that case, your take indeed seems cleaner

[mantoni]

Alternatively, there could be an if-statement around sinon.stub(object, prop) to check whether it's already stubbed.

[mroderick]

Needs a rebase

[mantoni]

@mroderick was already on it ;)

[mroderick]

Will you also make a PR into https://github.com/sinonjs/sinon/tree/v1.17 branch, so we can publish a new 1.17.x version?

[mroderick]

(yes, we really need to get back to having master as the branch we're shipping from)

[mantoni]

Ah, good point. Will do.