John Spackman

I think you'd have to add core-js to the compiler and then also add `corejs: 3` to the code at https://github.com/qooxdoo/qooxdoo-compiler/blob/master/source/class/qx/tool/compiler/ClassFile.js#L322-L348 If you wanted to submit a PR that would...

How about compiling it on first run into the ~/.qooxdoo directory (which is also used for configuration and other data). We already track the version number of the current qx,...

do you mean a hook that did `rm -f ./source/resource/qx/tool/website/build` ? That would be fine (so long as a future fix doesn't change that to `git clean -dfx` 😱;) )...

i completely agree; I would also like it if there are just warnings, those warnings are picked up and output into the console during app startup

Same thing happens for me - using it for the first time, and following the example; the picker pops up, and you can search etc, but there is no way...