Add nestedRoutes to @react-router/fs-routes

[okalil]

The @react-router/fs-routes package should export a foldersRoutes function, that create route config from the file system using a convention that matches Remix v1's route file naming, as an alternative to flatRoutes.

[brophdawg11]

Linking the PR with a POC implementation we can re-open if this moves forward: #12648

[brophdawg11]

To quote the new Governance doc:

Routing and Data Focused. Focus on core router-integrated/router-centric APIs and avoid adding first-class APIs that can be implemented in user-land

I think my gut reaction here is that this might be better off as a community package. We moved away from this convention in v2 and carved off @remix-run/v1-route-convention for folks who didn't want to migrate to flat routes. Can that package be used with @react-router/remix-routes-option-adapter?

We specifically put that in a separate repo because it wasn't the primary approach anymore and because it was mostly considered stable/frozen and wasn't really going to get the same level of maintenance as the other packages. I think the same holds true today - we don't necessarily want to bring this code in-house again because then it's one more thing we need to document/maintain.

We moved to routes.ts to avoid trying to solve file-based-routing and so folks could much more easily write their own conventions. flatRoutes exists again as a very simple first-class convention but also mostly for migration from v2. I don't think we want to maintain other first-class conventions since we've found that there's simply just not a convention that makes enough poeple happy to so we want out of the convention game entirely :).

[okalil]

Agreed. Combining @remix-run/v1-route-convention with @react-router/remix-config-routes-adapter was suggested a while ago in this Discord thread. We could mention this solution in the "Upgrading from Remix" doc to help users migrating from Remix v1 to React Router v7.

[brophdawg11]

yeah that's a good idea - do you want to open a PR to update that doc?

[okalil]

Linking here: #13921