[SIMPLE PATCH READY] Simple hack for compatibility with Turbopack (NextJS)

[Palid]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch @lingui/[email protected] for the project I'm working on.

I've been trying to setup turbopack with my project due to enormous compilation times, and figured out why things do not work as expected - it's the loader expecting webpack environment, even though it's not really doing anything with the module definitions.
With a simple change, the loader is now turbopack-swc-compliant.
Maybe there's a better way to figure out

Just for documentation reason, I'm additionally including my next.config.js, so that documentation for NextJS+SWC loader+Turbopack can be improved in the future. :)

/** @type {import('next').NextConfig} */
const nextConfig = {
  reactStrictMode: true,
  experimental:
  {
    swcPlugins: [["@lingui/swc-plugin", {}]],
    turbo: {
      resolveExtensions: [
        ".mdx",
        ".tsx",
        ".ts",
        ".jsx",
        ".js",
        ".mjs",
        ".json",
        ".po",
      ],
      rules: {
        "*.po": ["@lingui/loader"],
      },
    },
  }
};

module.exports = nextConfig;

The usage differs a little bit after using Turbopack, as it's going to be just direct imports like shown below.
You no longer need the prefix of @lingui/loader! before your imported .po files!

async function loadLinguiMessages(lang: Lang) {
  if (process.env.NODE_ENV === "development") {
    return (
      (await import(
        `src/locales/${lang}/messages.po`
      )) as MessagesFile
    ).messages;
  } else {
    return translations[lang].messages;
  }
}

Package versions, but most likely any nextjs version with turbopack will have the same problem:
"next": "^14.1.0",
"@lingui/loader": "^4.6.0",

I might try to solve this with a proper PR, but adding a simple patch like this is definitely better than just leaving it be!

Here is the diff that solved my problem:

diff --git a/node_modules/@lingui/loader/dist/index.cjs b/node_modules/@lingui/loader/dist/index.cjs
index e478911..75c8e0a 100644
--- a/node_modules/@lingui/loader/dist/index.cjs
+++ b/node_modules/@lingui/loader/dist/index.cjs
@@ -45,7 +45,7 @@ Please check that \`catalogs.path\` is filled properly.
   const strict = process.env.NODE_ENV !== "production";
   return api.createCompiledCatalog(locale, messages, {
     strict,
-    namespace: this._module.type === "json" ? "json" : "es",
+    namespace: '_module' in this ? this._module.type === "json" ? "json" : "es" : 'es',
     pseudoLocale: config.pseudoLocale
   });
 };

This issue body was partially generated by patch-package.

(I have decided to leave this template, as it's pretty slick and I think more people could use it. 😄 )

[timofei-iatsenko]

Thanks for the patch. Do they have documentation about compatibility of turborepo with webpack loaders?

As far as I understand from your patch when loader is executed by turborepo, there is no this._module variable, and it probably crashes when it accesses this._module.type. Am I right?

Just for context:

condition:

namespace: this._module.type === "json" ? "json" : "es",

Made to overcome the issue with webpack. Webpack doesn't allow (at least with public methods) switching type of the module in the loader. It means if you're loading "*.json" module through loader webpack expects json output from this loader. When you load any unknown to webpack module such as *.po or *.png file, webpack expects a valid ES module as output.

So this poses a problem, lingui user may load and compile catalog using *.json extension (lingui or minimal catalog formats) and using *.po format. Loader should work for both of the cases. That's the purpose of this condition.

[Palid]

@thekip It does not break compat with webpack by checking if we have this._module though. If we do - just go through with webpack part, if we don't we're probably in different bundler (e.g. turbopack).

It's just a quick&dirty hack to make sure this works, as turbopack makes compilation so much quicker.

[Palid]

@timofei-iatsenko I think the problem is that for turbopack you need to define your extensions explicitly, and it indeed is missing this._module, so if you do not define supporting extensions in the config (see first post) it will not be imported.

Do I have a green light to add a PR for this, with a comment that this path is explicitly added for solving problems with different builders than webpack (e.g. turbopack)?

[timofei-iatsenko]

@Palid yes please, create a PR with this patch. Also it would be good to add a doc somewhere about how to setup for turbopack, but i haven't found a good place. We have a React Server Components page, which is basically describing nextjs setup, but due to the name of this article no one will expect turbo pack configuration tips there.

@andrii-bodnar may be you can suggest a good place for that doc? Maybe just create a separate article "Turbopack Integration"

[andrii-bodnar]

What about creating a new page Turbopack Project within the Getting Started section? Right after the Vite Project item in the sidebar.

[mrmckeb]

Hi @Palid, this isn't working for me in the latest RC (RC2), I'm getting "ReferenceError: i18n is not defined". Have you managed to test the RC out yet?

Note that the config should now be:

export default {
  reactStrictMode: true,
  experimental: {
    swcPlugins: [["@lingui/swc-plugin", {}]],
    turbo: {
      rules: {
        "*.po": {
          loaders: ["@lingui/loader"],
          as: "*.js",
        },
      },
    },
  },
};

[Palid]

@mrmckeb I'll have a look today, using this config at work and it works properly. I'll double check what's missing and get a PR ready next week.

[timofei-iatsenko]

Guessing from the error message it might be not related to loader itself, because there are no i18n variable inside. It rather might be related to macro and runtime execution. But it's just a guess.

[mrmckeb]

I've just tested this with Next.js 15, which released yesterday and I'm getting the same issue.

I think it may be to do with the macro, but I haven't dug in yet sorry.

Error:

ReferenceError: i18n is not defined

Line from the error (where t is from "@lingui/macro"):

  111 |     <div>
  112 |       <Head>
> 113 |         <title key="title">{t`Translated text`}</title>
      |          ^
  114 |         <meta
  115 |           key="description"
  116 |           name="description"

This thread indicates that there may be a bug with the plugin, perhaps an issue with how Turbopack loads SWC plugins?

[Palid]

@mrmckeb could you try to get me a repro repo? There's so many moving parts in here!

[andrii-bodnar]

What about creating a new page Turbopack Project within the Getting Started section? Right after the Vite Project item in the sidebar.

Since the setup section has been heavily refactored and changed for Lingui v5 (#2060), I'd suggest adding a new section to the Installation and Setup > Build Tools documentation.

[carstenblt]

With NextJS 15 being released, a lot more people will run into problems with turbopack.

[glekner]

can we get a status here? is this patch safe to use with turbopack? or should we wait for v5?

[Trosterud]

This thread is nr 1 ranking in google when searching "lingui turbopack" 👍

[timofei-iatsenko]

We've released @lingui/[email protected] which is compatible with Next 15.

I prepared an example with Turborepo and swc in next 15. You can check the changes here #2073

The turborepo in that example works without any additional changes from the lingui loader side.