experiments.css generate wrong url path

[ahabhgk]

Bug report

Case 1: publicPath is not "auto"

What is the current behavior?

With following webpack config:

// webpack.config.js
module.exports = {
  entry: 'index.css',
  output: {
    publicPath: 'aaa.com/aa/',
  },
  module: {
    rules: [{ test: /\.png$/, type: 'asset/resource' }],
  },
  experiments: {
    css: true,
  },
}

/* index.css */
.a {
  background-image: url(./bg.png);
}

will generate:

.foo {
  background-image: url(bg.png); /* <-- wrong */
}
head{--webpack-main:\.\/index\.css;}

What is the expected behavior?

It should generate:

.foo {
  background-image: url(aaa.com/aa/bg.png);
}
head{--webpack-main:\.\/index\.css;}

Case 2: publicPath is "auto"

What is the current behavior?

With following webpack config:

// webpack.config.js
module.exports = {
  entry: 'index.css',
  output: {
    // publicPath: "auto" is default value
    cssFilename: 'css/[name].css',
    assetModuleFilename: 'assets/[name][ext]',
  },
  module: {
    rules: [{ test: /\.png$/, type: 'asset/resource' }],
  },
  experiments: {
    css: true,
  },
}

/* index.css */
.a {
  background-image: url(./bg.png);
}

will generate:

.foo {
  background-image: url(assets/bg.png); /* <-- wrong */
}
head{--webpack-main:\.\/index\.css;}

What is the expected behavior?

It should generate:

.foo {
  background-image: url(../assets/bg.png);
}
head{--webpack-main:\.\/index\.css;}

Other relevant information:
webpack version: 5.76.3
Node.js version: 18
Operating System: osx

[alexander-akait]

Thank you for report, I will move it inside #14893, because it is still under experiments, we can have many bugs