when publishing npm package, should I use src of dist

When publishing some javascript to npm as a library, should I set the "main" in pacakge.json to "dist/index.js" or my "src/index.js"?

Suppose that the library is built with webpack, and may be used with projects in webpack.

what will be the difference between two options. will webpack be able to do tree shaking in both options?

Thanks!

via ryang