Does Next.js support custom entries in the package.json exports field?

[idbartosz]

Question: Does Next.js support custom entries in the package.json exports field?

Usecase:
In a monorepo that contains a component package, I've got some custom entries defined for various tools and environments. So far every tool respected the custom entires and everything worked smoothly. But in the case of Next.js I'm not able to force it to use the custom next entry, it always tries to read the "." or ".": { "import": "..." } which in my case ends up in an error message Module not found: Package path . is not exported from package ....

Solutions tried:

• Adding a resolve.conditionNames = ['next'] to the weback configuration in next.config.js [1]
• Adding node options to the development script "dev": "NODE_OPTIONS='--conditions=next' next dev" [2]
• Trying both at the same time

[1] https://webpack.js.org/configuration/resolve/#resolveconditionnames
[2] https://nodejs.org/api/packages.html#resolving-user-conditions

Example:
Exports field defined in component package.json

  "exports": {
    ".": {
      "storybook": "./src/index.ts",
      "next": "./dist/index.js",
    }
  }

[arrizalamin]

I solved this with a webpack plugin:

class NextEntryPlugin {
  apply(compiler) {
    compiler.hooks.afterEnvironment.tap("NextEntryPlugin", () => {
      compiler.options.resolve.conditionNames.unshift("next");
      compiler.options.resolve.mainFields.unshift("next");
    });
  }
}

[jgoux]

Hey @arrizalamin I'm trying to do the same with Next.js v13.4.2 and it doesn't seem to work. Could you provide the full webpack config example?

[joostmeijles]

Appending to conditionNames works for me:

export function webpack(config) {
  const name = "myConditionName";

  class NextEntryPlugin {
    apply(compiler) {
      compiler.hooks.afterEnvironment.tap("NextEntryPlugin", () => {
        compiler.options.resolve.conditionNames = [...compiler.options.resolve.conditionNames, name]
      });
    }
  }

  config.plugins.push(new NextEntryPlugin());
}

[jgoux]

@timneutkens Would it be possible to turn this discussion into an issue? I would expect transpilePackages to honor tsconfig.json.

So if I define:

"compilerOptions": {
  "customConditions": ["snaplet_development"]
}

I would expect Next.js to match this condition when resolving the external packages.

And even better, if the external package is detected as a Typescript project reference, I would also expect Next.js to pick-up the external package's own tsconfig.json to resolve its internal path aliases. 😄

Those are the two things I'm missing to make Next.js great in TypeScript monorepos.

[Kuchasz]

Hi @jgoux did you found out how to make it to work? If not - have you found any workarounds?