This project demonstrates a performance issue with webpack regarding treeshaking. The app exports a react component that references a Component1 from one of the two possible packages from under static_node_modules. The two packages are ESM modules and marked as side effect free.

1. npm install
2. npm run build Initially we build the app referencing a module that has only a simple Component1 exported. In this case compilation takes less than a second.
3. Uncomment line 5 and comment line 3 in index.js.
4. npm run build This time we are building the app referencing a module containing that same Component1 but also a Component2 which is much heavier. Although we are not importing Component2 the built time gets ~12x longer.

In addition, note that: in webpack useExports optimization is turned off and in both cases we get the same results in dist (without Component2), based on this assuming that webpack indeed doesn't include the subtree of Component2 based on tree shaking; but compilation or subtree discovery still happens.