How to debug npm version of OpenFL

Is there any way to produce npm build of OpenFL debuggable in browser?
I see in sources dist directory in result of build process, but it is linked with lib/_gen files which i guess is just js output produced by haxe compiler on real OpenFL .hx sources.
This output is unreadable and what i want is to find the way to link it with real .hx classes.

Do the source maps properly map back to the _gen directory? If the source maps do not link, then it would be good for us to at least get that working. If it does already, could you give an example of what you’re seeing that feels unreadable? Usually that output should be fairly consistent with the original Haxe source.

We build for NPM by going through a Haxe macro to generate JS modules out of each Haxe class, then use Webpack to combine these into the final output.