Allow private invocation of ruby2_keywords

[marcotc]

Fixes #1712

#ruby2_keywords can be sometimes private: https://github.com/ruby/ruby2_keywords/blob/92ad9c5c3fff591b8383ada8b93c3da1279d24ad/lib/ruby2_keywords.rb#L1-L12

We already accounted for this by passing true to respond_to?(:ruby2_keywords, true), but we didn't invoke it with a private-safe way in case it was actually private. This PR makes such change.

[gedimin45]

Thanks for the amazingly swift fix @marcotc! Looking forward to the release so I can put this into production 🙂

[ivoanjo]

Thanks @marcotc for the lightning fast fix.

I think it's definitely worth merging and releasing, but I don't quite understand why this happened in #1712. The backtrace mentions Ruby 2.4.0, which definitely did not have ruby2_keywords support. I thought perhaps that the ruby2_keywords compatibility gem was in use, but I tried every version from 0.0.0 to the latest released 0.0.5 and this method was still not private for procs there.

So I'm left wondering where that ruby2_keywords monkey patch was coming from.

Second observation: cthread.rb has been really annoying to get right. I plan to replace it with a better approach and completely delete it, and it cannot arrive soon enough.

[marcotc]

this method was still not private for procs there.

@ivoanjo I was thinking the same thing, but I feel like a program can "mess up" the global Proc class by mixing-in the private Module#ruby2_keywords somewhere 🤷. Given we have empirical evidence, I'm incline to believe it :)

[ivoanjo]

@ivoanjo I was thinking the same thing, but I feel like a program can "mess up" the global Proc class by mixing-in the private Module#ruby2_keywords somewhere 🤷. Given we have empirical evidence, I'm incline to believe it :)

Oh yeah! That's exactly what I meant to convey as well -- I'm curious what's up in this case, but since a) we have evidence this can happen + b) the fix is trivial and does not impact customers or our work at all + c) hopefully this whole thing will be removed soonish, I think it's 100% a win to merge this in anyway :)