summary: 'Tree shaking with Webpack and the Terser plugin'
updated: '2020/06/17'Why is Webpack not tree-shaking pickOwnProps() out of coreUtil?
It's OK that both omit() and pick() (also in coreUtil) are in the resulting bundle because chooseOwnProps() can't know which one it will need until runtime, but pickOwnProps() is never called by anything in the bundle code...
I looked at https://webpack.js.org/guides/tree-shaking/ and https://webpack.js.org/configuration/optimization/ options, and they were already set the right way!
Finally, I was able to verify that Webpack's Terser plugin is also doing some optimization (likely when minify: true) and removing dead code from the Prod build, even though there's still some dead code in the Dev build, which is of less concern.
So Webpack does some tree shaking, and then Terser runs and does some final pruning to get rid of the loose branches that got stuck in other branches after they were cut. 🙂