Retain spy function names and fix spy.named(name)

[mantoni]

Purpose (TL;DR) - mandatory

• Let spies have the same name as the function they wrap
• Change the name property in spy.named(name), not just the displayName (used for sinon error messages)

Fixes #250

Background (Problem in detail)

We used to retain the name of spied functions, but this has been lost along the way at some point.

There is #950 which shows in the issue description that the name property of a spy reflected the original function name. However, the test that is verifying this was added later and it hard coded the name to "proxy".

I think this dates back to the old times when we used eval to generate the spy function.

Solution - optional

This change verifies that a name can be configured on the function – unfortunately this is inconsistent across (old but supported) browser versions – and then configures the name using the same property descritor flags as the original value.

How to verify - mandatory

1. Check out this branch
2. npm install
3. npm test
4. npm run test-cloud

Checklist for author

• npm run lint passes
• References to standard library functions are cached.

[coveralls]

Pull Request Test Coverage Report for Build 2811

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 94.109%

---

Files with Coverage Reduction	New Missed Lines	%
sinon/spy.js	2	89.86%

Totals
Change from base Build 2809:	-0.04%
Covered Lines:	1657
Relevant Lines:	1725

---

💛 - Coveralls

[mroderick]

The code in this change looks very similar to the code in the next change. Would it be wise to extract it to a shared function? Perhaps even put that function in @sinonjs/commons?

[mantoni]

Yes, I had the same thought, but in one case we're just using one descriptor as is, in the other case we modfy the value. Extracting a function produces more code and would include a superfluous value assignment for one of the cases. So I decided against it for clarity.

I am treating commons as a toolbelt for shared functions. This is a Sinon only feature so far. We can move it if we want to reuse it elsewhere.

[mroderick]

THUNDERBIRDS ARE GO!

[mantoni]

Released in v7.2.7.