Fix wrapper.attributes() method

[tianyong90]

#263

[eddyerburgh]

Thanks so much for this PR, embarrassing that this slipped through. Could you please add tests. We need one for the wrapper, one for the wrapper-array, and one for error-wrapper

[tianyong90]

Sure, I am starting working on it. 😄

[tianyong90]

@eddyerburgh Hi, after reviewing the tests, I found that these needed unit tests are already exists and there's no need to change them，none of them failed.

[eddyerburgh]

Hi @tianyong90 . These are bad tests if they passed when the code was buggy. Would you like to investigate why they were passing when the code was returning undefined? If not, I can merge and investigate myself. Thanks for the PR 😀

[tianyong90]

Aha, Finally found out that it seems that it's a bug in the dist but not in src, perhaps there's something wrong with the bounding tools or configuration. Just like shown in the picture above, the spread operator is transformed to [].concat(), this is the reason why unit tests all passed, but broken in my actual use.
To fix it, you can just merge the PR, or make some change with the building process.

[eddyerburgh]

Great find, thanks for the PR 🙂