An emacs' Feature Development

So, in https://lists.gnu.org/archive/html/emacs-devel/2020-10/msg00691.html there's a proposal for an optimization in emacs, adding empty-directory-p so that elisp users don't have to (null (directory-files dir-name nil 'nodots t))).

And it makes sense to have a faster way. The person that proposed this improvement proposed a solution too. And it was a good one!

Then, Eli proposed something else. Some alternative implementation that:

• Allows to solve the problem at hand, 
• Reuses existing code by adding a 'limit' to directory-files
• Easier to implement
• Makes the implementation more stratified. You can still create empty-dir-p by calling directory-files
• in case of passing that limit count to directory-files, we still get a list of files instead of a boolean. It's richer information, in case we need it.
  

After that, the conversation goes on by trying to figure out if the partial list of files will be useful at some point, or it's adding indeterminism and no value, and finding a balance on simplicity and usefulness. 

All in all, a very good end-to-end conversation about a feature, its implications and its implementations with its corner cases and usability. Every time I see these conversations happening I feel this joy... I love when they happen in my team.

PS: Needless to say, this is a "simple" feature compared to bigger and more complex discussions going on in emacs-devel (which are hard problems that have no perfect solutions). But it's a good case study and there's something to be learned there about approaches, discussions, and building together.

Thanks to everyone involved!