Without from option PostCSS could generate wrong source map and will not find Browserslist config. Set it to CSS file path or to undefined to prevent this warning.

[kud]

Hello,

In my custom webpack configuration, I've got this error when I use postcss.

      {
        test: /\.css$/,
        exclude: /\.module\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          {
            loader: "css-loader",
            options: {
              modules: false,
              importLoaders: 1,
              import: true,
            },
          },
          {
            loader: "postcss-loader",
            options: {
              postcssOptions: {
                plugins: [
                  ["autoprefixer"],
                  ["postcss-custom-media", { importFrom: [{ customMedia }] }],
                ],
              },
            },
          },
        ],
      },

but I don't know what to specify about from.

The doc says:

from: the input file name (most runners set it automatically).

but it seems to be not my case.

Do you have any idea how to fix this?

Thank you.

[ai]

from have to be set only if you use low-level PostCSS API.

For webpack, you do not need from option in loader options (postcss-loader set from automatically).

A few ideas why you have this warning:

1. You may use very old postcss-loader
2. It may be generated by some option tool, which use postcss.parse() or postcss().process() inside. Check postcss-custom-media sources and npm ls

[kud]

Thank you so so much @ai for your fast answer.

Current versions:

    "postcss-custom-media": "8.0.0",
    "postcss-loader": "6.1.1",
    "postcss-reporter": "7.0.2",

I'll check asap the custom-media sources. :)