Proposal: warn if function name contains uppercase letters

[sasa1977]

Recently I've encountered a situation in a code review where the author named the function to_CSV. This immediately stroke me as unusual/non-idiomatic (see e.g. Plug.HTML.html_escape as a counterexample). After thinking a bit about it, I can't really come up with an example where using uppercase name would be idiomatic, so I thought of writing a credo check. I have a basic first draft (code is available here), and I wanted to see if you'd be interested in moving this check to credo? If so, let me know and I'll prep a PR where we can discuss the details.

[NobbZ]

Shouldn't this be handled by https://github.com/rrrene/credo/blob/master/lib/credo/check/readability/function_names.ex?

Major part of work is done in this line of code:

https://github.com/rrrene/credo/blob/master/lib/credo/code/name.ex#L102-L104

So to_CSV should already be disapproved by this check.

[sasa1977]

Oh, I totally missed that because the error is not reported (I just double checked, and it's indeed not reported). Since credo didn't complain about it, I just assumed that this is not verified. It appears there is a bug in this check, so I'll close this issue and investigate further.

Thanks!

[sasa1977]

FYI, I submitted a fix (and a couple of other improvements) in #676