Translated routing and more for Next using Next regular file-base routing system

• Features
• Motivation
• How to
  • Basic usage
    1. Wrap you next config with the next-translate-routes plugin
    2. Define your routes
    3. Wrap you _app component with the withTranslateRoutes hoc
    4. Use next-translate-routes/link instead of next/link
  • Advanced usage
    • Configuration
    • Constrained dynamic paths segments
    • Ignoring a path part
    • Complex paths segments
    • Custom route tree
• How does it works

• Translated paths segments
  Ex: /contact-us and /fr/contactez-nous.
• Complex paths segments (path-to-regexp synthax)
  Ex: /:id{-:slug}?/
• Constrained dynamic paths segments (path-to-regexp synthax)
  Ex: /:id(\\d+)/
• No duplicated content (SEO)
  Simple rewrites would make a page accessible with 2 different urls which is bad for SEO.
• Auto-redirection to correct translated path
  Ex: /fr/english/path redirects to /fr/french/path
• No custom server needed!
  Next automatic static optimization remains available.

See it in action: https://codesandbox.io/s/github/hozana/next-translate-routes/tree/master

Note: Next-translate-routes does not work with Next html static export, since internationalized routing is among static html export unsupported features.

To build a fully internationalized website, one need to translate url segments: it is important for UX and SEO. For now, Next only ship with locale prefixes (see Next.js internationalized routing doc).

The next-routes package allow fully internationalized routing but it is no longer maintained, and it is designed without the latest Next api, such as internationalized routing, new data fetching methods, automatic static optimization.
To be able to use theses, a new approach is needed. Next.js provides it with Redirects and Rewrites, but:

• the main problem is that writing the rewrites and redirects to translate all the routes by hand is long, boring, error-prone, and hard to maintain.
• an other problem is that by default, the file path works with all the locale prefixes: it creates 2 urls for the same content, which is not good for SEO. This problem can be worked around by creating redirects from /${localePrefix}/$(filePath) to /${localePrefix}/$(localePath), but it creates a lot more complexity to write by hand and maintain.

Check the example folder to see next-translate-routes in action. Some advanced techniques are shown there too: they may seem complicated but those 4 steps should cover most of the cases.

Import the withTranslateRoutes from next-translate-routes/plugin.

// next.config.js
const withTranslateRoutes = require('next-translate-routes/plugin')

module.exports = withTranslateRoutes({
  // Next i18n config (mandatory): https://nextjs.org/docs/advanced-features/i18n-routing
  i18n: {
    locales: ['en', 'fr', 'es', 'pl'],
    defaultLocale: 'pl',
  },

  // ...Remaining next config
})

You can add a _routes.json, or a _routes.yaml, file in the pages folder, and in the every subfolder where you want to define routes.

Given a folder structure like so, you can add a _routes.json in /pages/ and in /pages/section/.

/pages/
 ├ section/
 | ├ page1.tsx
 | ├ page2.tsx
 | └ _routes.json
 ├ somewhere/
 | └ else.json
 ├ _app.tsx
 ├ about.tsx
 ├ contact.tsx
 └ _routes.json

In /pages/section/, the _routes.json file could look like this.

// `/pages/section/_routes.json`
{
  "/": {
    "es": "seccion" // Folder path in es
  },
  "page1": {
    "default": "article", // Overwrite the default page path (fallback)
    "es": "articulo"
  },
  "page2": "definition", // Overwrite the page path for all language
}

The "/": { ... } part define the folder paths, each other section define the paths of a page file in this folder:

• page1 will be accessible at /seccion/articulo in es, and at /section/article in other languages,
• page2 will be accessible at /seccion/definition in es, and at /section/definition in other languages.

You don't need a _routes.json file in folder where you don't customize anything. If it is empty, then delete it. Here, the /somewhere/ subfolder does not have any _routes.json file.

Then, in /pages/, the _routes.json file could look like this.

// `/pages/_routes.json`
{
  "/": {
    "pt": "blog" // As we are in the root pages folder, this will add a "blog" path prefix for all pages in pt
  },
  "contact": {
    "es": "contactar",
    "pt": "contatar"
  }
}

In the root pages folder, the "/": { ... } part of the root _routes.json allows to add a different basePath for each language or only some language, like "blog" in pt here:

• about will be accessible at /blog/about in pt and at /about in other languages,
• contact will be accessible at /blog/contatar in pt, at /contactar in es and at /contact in other languages,
• page1 will in fact be accessible at /blog/section/article in pt,
• page2 will in fact be accessible at /blog/section/definition in pt.

// `/pages/_app.js`
import { App } from 'next/app'
import { withTranslateRoutes } from 'next-translate-routes'

export default withTranslateRoutes(App)

Or:

// `/pages/_app.js`
import { withTranslateRoutes } from 'next-translate-routes'

const App = ({ Component, pageProps }) => {
  // Custom code...

  return <Component {...pageProps} />
}

export default withTranslateRoutes(App)

next-translate-routes extends Next Link to translate routes automatically: import it from 'next-translate-routes/link' instead of 'next/link' and use as you ever did.

import React, { useEffect, useState } from 'react'

import Link from 'next-translate-routes/link'

const MyLinks = (props) => {
  const { locales } = useRouter()

  return (
    <>
      <Link href="/file/path/to/page">Current locale</Link>
      {locale.map((locale) => (
        <Link
          href={{ pathname: '/file/path/to/[dynamic]/page', query: { dynamic: props.param, otherQueryParam: 'foo' } }}
          locale={locale}
          key={locale}
        >
          {locale}
        </Link>
      )}
    </>
  )
}

Check the example folder to see some advanced techniques in action.

Next-translate-routes is configurable by adding a translateRoutes key in Next config that accept an object of the following NTRConfig type.

type NTRConfig = {
  debug?: boolean
  routesDataFileName?: string
  routesTree?: TRouteBranch<L>
  pagesDirectory?: string
}

/** Non generic version of the TRouteBranch type for better readability, where the generi L prop is set to `'en' | 'fr'` */
type TRouteBranchEnFr = {
  name: string
  en: string
  fr: string
  children: TRouteBranchEnFr[]
}

  translateRoutes: {
    debug: true,
    routesDataFileName: 'routesData',
  }

When debug is set to true, you will get some logs, both in the server terminal and in the browser console. If routesDataFileName is defined, to 'routesData' for example, next-translate-routes will look in the pages folder for files named routesData.json or routesData.yaml instead of the default _routes.json or _routes.yaml. If routesTree is defined, next-translate-routes won't parse the pages folder and will use the given object as the routes tree. If you uses it, beware of building correctly the routes tree to avoid bugs.

// `/pages/blog/[id]/_routes.json`
{
  "/": ":id(\\d+)", // Constrain a dynamic folder segment (to be a number here)
  "[slug]": ":slug(\\w+)", // Constrain a dynamic page segment (to be letters here)
}

For a catch all route: "[...path]": ":path*".

This will ignore the blog path segment:

// `/pages/blog/_routes.json`
{
  "/": "."
}

It can be done for some lang only and not others.

// `/pages/blog/_routes.json`
{
  "/": {
    fr: "."
  }
}

/!\ Ignoring a path segment can cause troubles.
Ex. Given the /a/[b]/[c] and /a/[b]/[c]/d file paths. [b] is ignored and the b param is merged with the c param: ":b-:c".
Then /a/b/c will be redirected to /a/b-c and that is fine.
But /a/b-c/d will be redirected to /a/b-c-d and that is not fine.

To handle this case, one can add a path-to-regex pattern to the default ignore token. Ex: '.(\\d+)', or '.(\[\^-\]+)'.
This path-to-regex pattern will be added after the segment name in the redirect.
Then /a/b(\d+)/c will be redirected to /a/b-c, and /a/b-c/d will not be redirected to /a/b-c-d.
/!\ This is only handled in default paths (i.e. "/": ".(\\d+)" or "/": { "default": ".(\\d+)" }), not in lang-specific paths.

// `/pages/blog/[id]/_routes.json`
{
  "/": "article{-:id}?-view", // Add prefix, optional prefix, suffix
}

It is also possible to create a path segment with 2 dynamic parameters. Ex: /articles/:id{-:slug}?.
First, create a path segment for each dynamic parameter: `/articles/[id]/[slug]. Then:

// `/articles/[id]/_routes.json`
{
  "/": ".", // Ignore the [id] segment
  "[slug]": ":id{-:slug}?" // Give the 2 params to the 2nd segment
}

If you want to avoid seeding _routes.json files in your /pages folder, you can directly create a routesTree object, and inject it in the next config as follow.

// next.config.js
const withTranslateRoutes = require('next-translate-routes')
const getRoutesTree = require('./getRoutesTree')

const routesTree = getRoutesTree()

module.exports = withTranslateRoutes({
  // Next i18n config (mandatory): https://nextjs.org/docs/advanced-features/i18n-routing
  i18n: {
    locales: ['en', 'fr', 'es', 'pl'],
    defaultLocale: 'pl',
  },

  translateRoutes: {
    routesTree,
  },

  // ...Remaining next config
})

routesTree must be of type TRouteBranch:

type TRouteBranch<Locale extends string> = {
  name: string
  paths: { default: string } & Partial<Record<Locale, string>>
  children?: TRouteBranch[]
}

One might need to mock next-translate-routes outside Next, for example in Storybook. It is possible as follow:

import { RouterContext } from 'next/dist/shared/lib/router-context'
import withTranslateRoutes from 'next-translate-routes'

  //[...]

  const TranslateRoutes = withTranslateRoutes(
    {
      defaultLocale: 'fr',
      debug: true,
      locales: ['fr', 'en', 'es', 'pt'],
      routesTree: { name: '/', paths: { default: '/' } }, // Mocked routes tree
    },
    ({ children }) => <>{children}</>,
  )

  return (
    <RouterContext.Provider value={Router.router}>
      <TranslateRoutes pageProps={{}} router={Router.router}>
        {children}
      </TranslateRoutes>
    </RouterContext.Provider>
  )

  // [...]

For Storybook, this piece of code can be used to create a decorator function.

• Next-translate-routes plugin parses the page folder and builds a routes tree object that contains the path tree and the information in the _routes.json files.
• The plugin then uses this information to build optimized redirects and rewrites, then add them to the next config object.
• Rewrites take care of displaying the right page for the translates urls, redirects take care of the urls that would give an unwanted access to the pages (and would create duplicated content).
• The plugin adds a webpack loader for the pages/_app file. This loader adds a data object (containing the routes tree object along with other config) as first argument of the withTranslateRoutes high order component that wrap the app.
• withTranslateRoutes makes this data available as a global variable, __NEXT_TRANSLATE_ROUTES_DATA.
• The translateUrl function uses this data to translate routes.
• The next-translate-routes/link leverages the translateUrl function to set the as prop of next/link to the translated url so that the link is aware of the true url destination (which is then available on hover, or on right-click - copy link for example).
• The withTranslateRoutes enhance the router by overriding the router context, to give translation skills to the router.push (which is used on click on a next/link), router.replace, and router.prefetch functions, using the translateUrl function too.