Next.js createPage helper with loader pattern

For the last two years I've been using a createPage helper with Next.js that
allows you to re-use some common features, like fetching data, checking roles or feature flags, etc.
This idea was originally posted by Rado Stankov and I've been using it ever since.

With the release of the app router in Next.js 13 I've been looking for a way to improve this pattern
and make better use of RSC (React Server Components), but didn't find a setup yet that I was fully happy with.

Earlier this week I came across a tweet from @matt_stobbs that showed the new
defineRoute function that will be introduced in React Router (and Remix) when it dawned on me that I could use this
to improve my createPage helper.

How it works

Here's an example how the new createPage helper is used in the Saas UI Pro starterkit.

import { notFound } from 'next/navigation'
import { z } from 'zod'

import { DashboardPage } from '#features/workspaces/dashboard'
import { createPage } from '#lib/create-page'
import { api } from '#lib/trpc/rsc.js'

const { Page, generateMetaData } = createPage({
  params: z.object({
    workspace: z.string(),
  }),
  searchParams: ['test'],
  loader: async ({ params }) => {
    const workspace = await api.workspaces.bySlug({
      slug: params.workspace,
    })

    if (!workspace) {
      notFound()
    }

    return {
      workspace,
    }
  },
  metadata: async ({ data }) => ({
    title: `Dashboard - ${data.workspace.name}`,
  }),
  component: ({ params, searchParams, data }) => (
    <DashboardPage
      params={params}
      searchParams={searchParams}
      workspace={data.workspace}
    />
  ),
})

export { generateMetaData }

export default Page

So what's happening here?

The createPage function is a factory function that returns a Page component and metadata or generateMetaData that can be exported from an app router page.tsx.

We can define params and searchParams using Zod schemas (or an array with the param names ['workspace']).
These then become available in the loader function that is called server-side to fetch the data for the metadata and page component.

In this example we're fetchin data from a tRPC procedure, but this could be any async function that returns the data needed for the page.
The return value of the loader function is then inferred by the metadata, and component handlers.

The component returned by the createPage is a React Server Component that wraps the DashboardPage component, which can be a regular client component, or another RSC.

Now we no longer have to import and move around types, params and searchParams are validated, and established a common pattern for fetching initial data for our metadata and page components.

Extending the helper

You can easily extend this helper with extra functionality, like role access.

const { Page, generateMetaData } = createPage({
  roles: ['admin'],
  component: ({ params, searchParams, data }) => (
    <AdminPage params={params} searchParams={searchParams} data={data} />
  ),
})

Source code

You can find the source code in this gist, there are still a few details I'm not certain about.

• Use safeParse for the params and searchParams?
• Should the component be wrapped with Suspense?
• Can we hydrate the data returned from the loader function easily to React Query.
• cache the loader function?
• Turn this into a library?

Please do leave a comment if you have idea's, suggestions or other feedback.

Thanks for reading :)