Issue #1936: Make the spy functions non enumerable so that printing it is more concise

[LouisBrunner]

Purpose

Improve issue #1936: Make the spy functions non enumerable so that printing it is more concise

Background

When printing a spy (which is often done by assertion libraries), the output takes a long chunk of space and make debugging really difficult. This PR removes the internal functions from this output, making the list smaller and more useful.

Solution

This PR expands the extend function to support extending using Object.defineProperty with enumerable: false. As configurable and writable are set to true, the rest of the codebase will still work as intended. Note that as indicated by @ehmicky in the original issue, the node REPL is not affected.

How to verify

[coveralls]

Pull Request Test Coverage Report for Build 2740

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 95.1%

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Files with Coverage Reduction	New Missed Lines	%
sinon/util/core/extend.js	1	89.8%

Totals
Change from base Build 2739:	0.01%
Covered Lines:	2051
Relevant Lines:	2118

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💛 - Coveralls

[mroderick]

Thank you for your pull request!

I am surprised that the valid-jsdoc rule didn't complain about this already, or I would have fixed it when I upgraded eslint-config-sinon.

Since you're touching these files anyway, would you mind turning the comments into JSDoc, so we can use them for future purposes?

[mroderick]

I re-ran the build in Circle CI, I guess it had a hiccup :)

[LouisBrunner]

I am not too familiar with JSDoc, are the comments fine like this?

I tested a bit and eslint's valid-jsdoc seems to only check comments that start with /**.

[mroderick]

I am not too familiar with JSDoc, are the comments fine like this?

If ESLint doesn't complain, then I guess they're good :)

I think that JSDoc comments are supposed to start with /**, which is why it didn't complain about the previous comments.

Thanks!

[mroderick]

This has been published as sinon@7.1.1