[GH-ISSUE #806] Shim `next/root-params` module with runtime getters #178

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opened 2026-05-06 12:37:55 +02:00 by BreizhHardware · 0 comments

BreizhHardware commented

2026-05-06 12:37:55 +02:00

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Originally created by @github-actions[bot] on GitHub (Apr 9, 2026).
Original GitHub issue: https://github.com/cloudflare/vinext/issues/806

Summary

Next.js added generated type definitions for next/root-params, which provides runtime getter functions for root layout parameters. The module already existed at runtime but now has build-time type generation that produces a root-params.d.ts file under .next/types.

Upstream

What changed

next/root-params exports async getter functions (e.g., lang(), locale()) for each root param discovered from App Router root layouts
Type generation: .next/types/root-params.d.ts is produced during next build, next dev, and next typegen
Root params are collected from layout routes in the route types manifest by scanning for the shallowest layout in each branch (root layouts)
Params can be string, string[], or undefined depending on whether they're optional, catch-all, or missing from some roots
Feature is enabled when experimental.rootParams or cacheComponents is true
The generated types are wired into next-env.d.ts via an ESM import

Impact on vinext

vinext needs to:

Add next/root-params to the shim map in resolveId so imports resolve correctly
Implement the runtime module — since vinext scans app/ directories for routing, it can detect root layout params and generate the appropriate getter functions
Consider type generation if vinext supports TypeScript project references or next-env.d.ts equivalent

This is primarily relevant for App Router apps that use root-level dynamic segments (e.g., app/[lang]/layout.tsx). The runtime behavior is the higher priority; type generation can follow later.

Originally created by @github-actions[bot] on GitHub (Apr 9, 2026). Original GitHub issue: https://github.com/cloudflare/vinext/issues/806 ## Summary Next.js added generated type definitions for `next/root-params`, which provides runtime getter functions for root layout parameters. The module already existed at runtime but now has build-time type generation that produces a `root-params.d.ts` file under `.next/types`. ## Upstream - Commit: https://github.com/vercel/next.js/commit/46e2114ea28a39aab4c04c2451aa462af14e62df - PR: https://github.com/vercel/next.js/pull/91019 ## What changed - `next/root-params` exports async getter functions (e.g., `lang()`, `locale()`) for each root param discovered from App Router root layouts - Type generation: `.next/types/root-params.d.ts` is produced during `next build`, `next dev`, and `next typegen` - Root params are collected from layout routes in the route types manifest by scanning for the shallowest layout in each branch (root layouts) - Params can be `string`, `string[]`, or `undefined` depending on whether they're optional, catch-all, or missing from some roots - Feature is enabled when `experimental.rootParams` or `cacheComponents` is true - The generated types are wired into `next-env.d.ts` via an ESM import ## Impact on vinext vinext needs to: 1. Add `next/root-params` to the shim map in `resolveId` so imports resolve correctly 2. Implement the runtime module — since vinext scans `app/` directories for routing, it can detect root layout params and generate the appropriate getter functions 3. Consider type generation if vinext supports TypeScript project references or `next-env.d.ts` equivalent This is primarily relevant for App Router apps that use root-level dynamic segments (e.g., `app/[lang]/layout.tsx`). The runtime behavior is the higher priority; type generation can follow later.