Faster routeTree formatting

[honzahruby]

Our app has ~1000 routes and the generated routeTree file is about 26k lines of code.

The time to regenerate routes improved with #3366 (12s -> 3.4s), but formatting is still the main bottleneck.

I'm proposing two solutions to this issue:

1. Cache results of formatting
   To minimize the size of the cache, I'm using a hash of the raw source as a key and the formatted output as a compressed buffer.
   https://github.com/TanStack/router/compare/main...honzahruby:fast-route-gen-cache?expand=1

   Measurements:

   • add or change route: 3.4s
   • no change to routes: 0.5s

---

2. Skip formatting of the existing routeTree context
   We always write the routeTree already formatted, so in most cases, it's safe to assume it is correctly formatted when being read. This would only not be true if the user had some custom formatting in place, which would be overridden by the default formatter anyway when regenerating the file due to route changes.
   https://github.com/TanStack/router/compare/main...honzahruby:fast-route-gen?expand=1

   Measurements:

   • add or change route: 1.2s
   • no change to routes: 1.0s

[schiller-manuel]

3. dont format at all?

[schiller-manuel]

disabling formatting should be straight forward. open a PR and we can get this in
might even make this the default since that file is not meant for human consumption

cc @SeanCassiere

[SeanCassiere]

Yeah, having an option for disabling the formatting of such HUGE route trees makes sense. Something like disableGeneratedRouteTreeFormatting?

Also, if you are not using Start, but rather just Router, you could turn off route-manifest generation. It should take out a bunch of unneeded JSON.

If you are opening a PR, please make sure that this surgically only applies to the generated route tree.

[schiller-manuel]

we should also disable router manifest generation by default and only enable it in start

[honzahruby]

@SeanCassiere Agreed, I happen to be the one working with you on disableManifestGeneration 😉

I'll open a PR and let you know.

[honzahruby]

#3678, also added test and documentation 🙏