How to know which polyfills are included by plugin-legacy

[kingyue737]

I found that even set the modernTargets as the latest browsers would include a large modern polyfill chunk. Is there a way to enable a debug mode to inspect which polyfills are included and why.

[sapphi-red]

This is possible by passing --debug legacy (vite build --debug legacy).
I'm not sure if there's a way to output the reason. plugin-legacy uses @babel/preset-env to decide what polyfill to inject, so maybe there's some information on that side.