Investigate dev-mode perf issues for fumadocs

[ssalbdivad]

Before migrating to fumadocs, there was a significant delay on saving a .ts file before you could see your changes reflected in browser while running pnpm dev.

Though fumadocs has been a significant improvement in many ways, this has actually substantially worsened. I recently was able to fix the --turbo flag on dev mode, but even with that enabled, I'm often seeing ~10 seconds to reload the home page and ~25 seconds on initial navigation to the docs section (down from over 50 seconds).

My best guess is somehow, twoslash is actually typechecking large portions of the repo in these cases to try and update inferred types. Typechecking the entire repo takes ~10 seconds locally, so that still doesn't account for all of it, but it's my best guess as to where to start for such extreme delays in such a small project.

Would love if someone better versed in Next.js could take a look and see if they can root cause it/find some potential improvements.

UPDATE: I did try removing twoslash and saw the compile time go from ~10s->~6sfor the homepage and ~25s->~6s for docs. Still seems pretty slow though...

[fuma-nama]

I had reached out to the Next.js team about the idea of lazy bundling - only compile MDX files when Next.js runtime requests it, which will significantly reduce initial time taken for compilation under dev mode.

Turbopack is still under the "make it work" stage, so in short term we probably cannot fix the problem

[ssalbdivad]

@fuma-nama Thanks for taking a look and for your great work on fumadocs! I have been frustrated a bit by some of Next's DX but your library has been so great it's been a big upgrade overall regardless👍

Would love to know if that ends up happening.