Conditional link rendering via `process.env.DOCUSAURUS_CURRENT_LOCALE` no longer works in Docusaurus v3

[adarSonmez]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

In Docusaurus v2, we used process.env.DOCUSAURUS_CURRENT_LOCALE in docusaurus.config.js to switch sidebar paths, navbar links, etc., based on the current locale. After upgrading to Docusaurus v3, the same pattern no longer has any effect: the config file is evaluated only once at build time and never re-evaluates per‐locale.

Reproducible demo

No response

Steps to reproduce

    let currentLocal = process.env.DOCUSAURUS_CURRENT_LOCALE;
    let sidebarLocal = currentLocal;

    if (currentLocal === 'en') {
      sidebarLocal = 'en';
    } else {
      sidebarLocal = 'tr';
    }

    module.exports = {
      i18n: {
        defaultLocale: 'tr',
        locales: ['tr', 'en'],
      },
      plugins: [
        [
          '@docusaurus/plugin-content-docs',
          {
            id: 'activities',
            path: 'projects/activities',
            routeBasePath: 'activities',
            sidebarPath: require.resolve(`./sidebars/${sidebarLocal}/activitiesSidebar.js`),
          },
        ],
      ],
      themeConfig: {
        navbar: {
          logo: {
            href: `/${currentLocal}`,
          },
        },
      },
    };

2. Build the site (yarn build) and serve.
3. Switch the locale via the dropdown to English.
4. Notice that the sidebar and logo links remain pointing at /tr/....

Expected behavior

• When switching to English, process.env.DOCUSAURUS_CURRENT_LOCALE should update so that:
  • sidebarPath resolves to sidebars/en/...
  • Navbar logo href becomes /en/

Actual behavior

• The value of process.env.DOCUSAURUS_CURRENT_LOCALE is fixed at build time and does not change per‐locale.
• All locale‐specific config remains at the default locale.

Your environment

No response

Self-service

• I'd be willing to fix this bug myself.

[slorber]

I doubt this is true, because we use DOCUSAURUS_CURRENT_LOCALE extensively internally on our own website, as many others.

Please provide a runnable repro to show the problem in action.

I'd also suggest adding console.log(process.env.DOCUSAURUS_CURRENT_LOCALE) to troubleshoot the issue and see what gets printed

[adarSonmez]

@slorber thank you for the answer. i will provide a small repro in 24h

[adarSonmez]

@slorber reproduction is ready! the issue can be tested in three area:

• url in footer
• address in footer
• main title

source code: https://github.com/adarSonmez/docusaurus_issue-11320_reproduction

live demo: https://venerable-travesseiro-0ead84.netlify.app/en/

[slorber]

Hmmm yes there is something weird going on in your repro.

I can't reproduce it on a newly initialized site.

You can fix your repro by using ESM instead of CJS for the config file (use export default config instead of module.exports = config)

We'll likely deprecate CJS config files in the future, so it's a good thing to migrate to ESM.

https://docusaurus.io/blog/releases/3.0#esm-ts-configs

[adarSonmez]

Thanks, Sébastien - switching to ESM fixed it.
I'll go ahead and close this now.