Well, considering that I wrote the andand gem that actually does extend the Object class, it should be clear that I am comfortable with the idea of selectively extending core classes.

However, I am also keenly aware that there are others with different viewpoints. For example, andand was first used in production on an application with a handful of developers and a medium-sized collection of classes.

I have done some work with another application that has dozens of developers in multiple locations and considerably more classes, almost an order of magnitude more. The developers on the second application are far more conservative about extending core classes.

I am also very sensitive to the downstream client problem. When working on your own project, you can do whatever you want. But when writing a gem or plug-in for others to use, you need to be much more conservative about introducing extensions, because they get them whether they want them or not.

For that reason, the rewrite gem doesn't use andand.