Here are the commits. Looks like the biggest backwards compatibility issue comes from the "Drop Angular" commit. He also changed the screw_ie8 option to be called ie8 now. A few bug fixes, too, but I'm definitely paraphrasing here.
Uglify is a mature and widely-used package. I use it and I love it. It's been years since uglify2, and I was excited to see this.
But... it appears that there are no release notes for version 3, apart from the three negative points at the top of the README: backwards incompatible, twice as slow on the latest Node, and still no ES6 (edit out of the box). No rationale for (or detail of) the breaking change is given. Really bizzare.
While the issue opener is quite brisk and curt, they hardly goes as far as overt rudeness. The blank non-response is astoundingly rude and dismissive in contrast.
Give me a break. The project maintainer is volunteering his time to help the javascript community and is doing a fantastic job fixing dozens of bugs and adding new optimizations and features - often the same day as issues are opened. Rather than nag him, step up and review the commits yourself and make a pull request implementing a ChangeLog.
> He also changed the screw_ie8 option to be called ie8
That's a shame, I always enjoy that silly bit of humour every time I scan my uglify configs!
I totally get why it's safer to not do that sort of thing, nonetheless it does have a certain charm when done sparingly. I wonder if the change was in response to some specific feedback / complaints?
Maybe in Victorian times using the word 'screw' would be considered offensive. The explanation is likely much more inoccuous. Using negative variable names is confusing and leads to programmer errors.
But... it appears that there are no release notes for version 3, apart from the three negative points at the top of the README: backwards incompatible, twice as slow on the latest Node, and still no ES6 (edit out of the box). No rationale for (or detail of) the breaking change is given. Really bizzare.