> skip some build steps
There was a change in Next 16, not Turbopack, that removed `ESLint` during `next build`: https://nextjs.org/blog/next-16#breaking-changes-and-other-u...
This behavior is the same whether you use Turbopack or webpack. It doesn't make sense for us to couple ourselves with ESLint when there are many viable alternatives. No other popular frameworks run ESLint automatically during builds. This change in Next 16 brought up closer to parity with other frameworks and bundlers.
> typescript validation
There's no change here with Turbopack. We do still run `tsc` automatically to check your types. That's part of `next build` and not Turbopack. However, we may remove this in the future for similar reasons.
There's no good reason for the bundler to call the typechecker. Bundlers strip types. Historically this was done with Babel in webpack. Modern versions of Next.js use SWC for type stripping in both webpack and Turbopack.
> aggressively cache node modules
We aggressively cache everything. We don't have special-casing for `node_modules`. See our blog post about our caching system: https://nextjs.org/blog/turbopack-incremental-computation
Interestingly vite does actually special-case and cache `node_modules`: https://vite.dev/guide/dep-pre-bundling
There are tradeoffs to both approaches, and I think Vite's choice makes sense in the context of their broader minimal-bundling-in-dev design, but it makes less sense for Turbopack (as well as webpack and Rspack) where we produce bundles in dev.