[Bug]: Comments not getting removed from CSS

[Daggron]

Describe the bug

We have added few comments in our css files but those comments are not getting removed from the build output of CSS.

PostCssConfig

// eslint-disable-next-line import/no-commonjs
module.exports = (broker) => {
  // eslint-disable-next-line import/no-dynamic-require
  const colors = require(`./src/adapters/${broker}/variables/variables`);
  return {
    plugins: [
      require('postcss-import'),
      require('postcss-custom-media')({
        importFrom: './node_modules/@smallcase/shringar/resolutions.css',
      }),
      require('postcss-mixins'),
      require('postcss-nested'),
      require('postcss-simple-vars')({
        variables: colors,
      }),
      require('postcss-flexbugs-fixes'),
      require('postcss-custom-properties')({
        importFrom: [
          './node_modules/@smallcase/shringar/variables.css',
          `./src/adapters/${broker}/variables/variables.css`,
        ],
        preserve: false,
        disableDeprecationNotice: true,
      }),
      require('cssnano')({
        preset: 'default',
      }),
     require('autoprefixer')({
        flexbox: 'no-2009',
      })
    ],
  };
};

Expected behaviour

The comments should be removed from the production build

Steps to reproduce

NA

Version

4.1.11

Preset

default

Environment

System:
    OS: macOS 13.0.1
    CPU: (8) arm64 Apple M1
    Memory: 61.06 MB / 8.00 GB
    Shell: 5.8.1 - /bin/zsh

Package details

─┬ @storybook/builder-webpack5@6.5.14
│ └─┬ css-loader@5.2.7
│   ├─┬ icss-utils@5.1.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-extract-imports@3.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-local-by-default@4.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-scope@3.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-values@4.0.0
│   │ └── postcss@8.4.19 deduped
│   └── postcss@8.4.19 deduped
├─┬ @storybook/manager-webpack5@6.5.14
│ └─┬ css-loader@5.2.7
│   ├─┬ icss-utils@5.1.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-extract-imports@3.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-local-by-default@4.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-scope@3.0.0
│   │ └── postcss@8.4.19 deduped
│   ├─┬ postcss-modules-values@4.0.0
│   │ └── postcss@8.4.19 deduped
│   └── postcss@8.4.19 deduped
├─┬ @storybook/react@6.5.14
│ └─┬ @storybook/core@6.5.14
│   └─┬ @storybook/core-server@6.5.14
│     └─┬ @storybook/builder-webpack4@6.5.14
│       ├─┬ postcss-flexbugs-fixes@4.2.1
│       │ └── postcss@7.0.39 deduped
│       ├─┬ postcss-loader@4.3.0
│       │ └── postcss@7.0.39 deduped
│       └── postcss@7.0.39
├─┬ autoprefixer@9.8.8
│ └── postcss@7.0.39
├─┬ babel-plugin-react-css-modules@5.2.6
│ ├─┬ postcss-modules-extract-imports@1.2.1
│ │ └── postcss@6.0.23
│ ├─┬ postcss-modules-local-by-default@1.2.0
│ │ └── postcss@6.0.23
│ ├─┬ postcss-modules-parser@1.1.1
│ │ └── postcss@5.2.18
│ ├─┬ postcss-modules-scope@1.1.0
│ │ └── postcss@6.0.23
│ ├─┬ postcss-modules-values@1.3.0
│ │ └── postcss@6.0.23
│ ├─┬ postcss-modules@1.5.0
│ │ ├─┬ css-modules-loader-core@1.1.0
│ │ │ ├─┬ postcss-modules-extract-imports@1.1.0
│ │ │ │ └── postcss@6.0.1 deduped
│ │ │ └── postcss@6.0.1
│ │ └── postcss@7.0.39
│ └── postcss@7.0.39
├─┬ css-loader@3.6.0
│ ├─┬ icss-utils@4.1.1
│ │ └── postcss@7.0.39
│ ├─┬ postcss-modules-extract-imports@2.0.0
│ │ └── postcss@7.0.39 deduped
│ ├─┬ postcss-modules-local-by-default@3.0.3
│ │ └── postcss@7.0.39 deduped
│ ├─┬ postcss-modules-scope@2.2.0
│ │ └── postcss@7.0.39 deduped
│ ├─┬ postcss-modules-values@3.0.0
│ │ └── postcss@7.0.39 deduped
│ └── postcss@7.0.39
├─┬ cssnano@4.1.11
│ ├─┬ cssnano-preset-default@4.0.8
│ │ ├─┬ css-declaration-sorter@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ cssnano-util-raw-cache@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-calc@7.0.5
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-colormin@4.0.3
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-convert-values@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-discard-comments@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-discard-duplicates@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-discard-empty@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-discard-overridden@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-merge-longhand@4.0.11
│ │ │ ├── postcss@7.0.39
│ │ │ └─┬ stylehacks@4.0.3
│ │ │   └── postcss@7.0.39
│ │ ├─┬ postcss-merge-rules@4.0.3
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-minify-font-values@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-minify-gradients@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-minify-params@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-minify-selectors@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-charset@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-display-values@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-positions@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-repeat-style@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-string@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-timing-functions@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-unicode@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-url@4.0.1
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-normalize-whitespace@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-ordered-values@4.1.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-reduce-initial@4.0.3
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-reduce-transforms@4.0.2
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-svgo@4.0.3
│ │ │ └── postcss@7.0.39
│ │ ├─┬ postcss-unique-selectors@4.0.1
│ │ │ └── postcss@7.0.39
│ │ └── postcss@7.0.39
│ └── postcss@7.0.39
├─┬ postcss-custom-media@8.0.2
│ └── postcss@8.4.19 deduped
├─┬ postcss-custom-properties@12.1.11
│ └── postcss@8.4.19 deduped
├─┬ postcss-flexbugs-fixes@5.0.2
│ └── postcss@8.4.19 deduped
├─┬ postcss-import@14.1.0
│ └── postcss@8.4.19 deduped
├─┬ postcss-loader@6.2.1
│ └── postcss@8.4.19 deduped
├─┬ postcss-mixins@8.1.0
│ ├─┬ postcss-js@3.0.3
│ │ └── postcss@8.4.19 deduped
│ ├── postcss@8.4.19 deduped
│ └─┬ sugarss@3.0.3
│   └── postcss@8.4.19 deduped
├─┬ postcss-nested@5.0.6
│ └── postcss@8.4.19 deduped
├─┬ postcss-simple-vars@6.0.3
│ └── postcss@8.4.19 deduped
├── postcss@8.4.19
└─┬ stylelint@14.16.0
  ├─┬ @csstools/selector-specificity@2.0.2
  │ └── postcss@8.4.19 deduped
  ├─┬ postcss-safe-parser@6.0.0
  │ └── postcss@8.4.19 deduped
  └── postcss@8.4.19 deduped

Additional context

No response

[ludofischer]

I have noticed this issue is using cssnano 4.1.11. You could try with cssnano 5, as we don't update cssnano 4 any more. Also it would be important to have some input CSS where cssnano fails to remove the comments, since cssnano does usually remove them.