As someone who works on Closure Compiler, this is one of my biggest gripes with the project. Things are getting better though! CC now supports node's module resolution algorithm. It works pretty well with Es6 imports but not so well with CommonJS (mostly because the exports are impossible to statically analyze).

Within Google, CC is heading towards being a an optimizing backend for other less painful languages such as Typescript (tsickle) and the yet-to-be-released J2CL compiler.

CC does pretty well with these examples (our debugger is not quite as flashy): https://closure-compiler-debugger.appspot.com/#input0%3D%252...