State of issuerLayer=="rsc" for the library authors

[timofei-iatsenko]

What is the improvement or update you wish to see?

Hello NextJs team,

I'm a maintainer of the Lingui https://lingui.dev/ which is i18n library with a focus on DX.

Recently we started a discussion how to support RSC without lacking a DX for our users and found that we need a possibility to resolve our Trans component to a different implementation depending on the issuer layer.

I ended up with my custom resolver for webpack which looks like this:

class LinguiTransRscResolver {
  apply(resolver) {
    const target = resolver.ensureHook('resolve');
    resolver
      .getHook('resolve')
      .tapAsync('LinguiTransRscResolver', (request, resolveContext, callback) => {

        if (request.request === TRANS_VIRTUAL_MODULE_NAME) {
          const req = {
            ...request,
            request: request.context.issuerLayer === 'rsc'
              // RSC Version without Context and will use React.cache to get current 
              // locale and message catalog
              ? path.resolve('./src/i18n/rsc-trans.tsx')
              // Regular version, using context to get Message Catalog
              : '@lingui/react',
          };

          return resolver.doResolve(target, req, null, resolveContext, callback);
        }

        callback();
      });
  }
}

However, request.context.issuerLayer === 'rsc' is an internal Next.js implementation detail, and I feel that using it in our library may break at any time.

• How safe is to use this property in a 3rd party code?
• Could you suggest a better alternative to solve the same issue?
• Could you consider making this property part of public api for library authors?

Related issues:

lingui/js-lingui#1698
lingui/js-lingui#1903

Lingui with RSC PoC: https://github.com/thekip/nextjs-lingui-rsc-poc/blob/main/next.config.js

[pawelblaszczyk5]

Maybe using package.json conditions would solve this and be more universal across RSC frameworks? There’s a “react-server” import/export condition for RSC 😃 Would that help there?

[timofei-iatsenko]

Good point. That makes sense.

[timneutkens]

Yeah definitely don't add a webpack plugin for this as it'll break in the future 👍 The react-server condition in package.json exports allows you to provide a separate implementation for React Server Components that is supported across all frameworks that support Server Components 💯

[timofei-iatsenko]

Is this react-server condition already supported by next?

[pawelblaszczyk5]

Is this react-server condition already supported by next?

Yes, it was supported from the first release, that’s part of React spec 😃
Example package utilizing it - https://github.com/vercel/react-tweet/blob/main/packages/react-tweet/package.json

[timofei-iatsenko]

Thanks for your answers, we will go this way.

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