[turbopack] Unable to get the configuration of PostCSS from package.json

[mogeko]

What version of Next.js are you using Turbopack in?

13.4.4

What package manager are you using / does the bug impact?

pnpm

What operating system are you using?

Mac

Describe the Bug

According to the document of postcss-load-config, PostCSS supports configuring it using the postcss field in package.json or a configuration file.

However, the postcss field in package.json is not working when I using PostCSS with Turbopack.

Then, I tried to create a .postcssrc.json and copied the same configuration into it, everything is in line with expectations.

Expected Behavior

Use postcss in package.json to configure PostCSS, which should get the same results as using a configuration file.

To Reproduce

1. Create a project that uses Next.js and PostCSS, for example: Next.js + Tailwind CSS Example
2. Removed postcss.config.js to prevent it from interfering with experiments
3. Configure Post CSS using postcss in package.json:

   "postcss": {
     "plugins": [
       "tailwindcss",
       "autoprefixer"
     ]
   }
   

4. Run Next.js with Turbopack:

   pnpm next dev --turbo
   

Reproduction Repo

https://github.com/mogeko/movisea

_PACK-2499

[long2ice]

Any news?