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css.PostCSS

{{ with resources.Get "css/main.css" | postCSS }}
  <link rel="stylesheet" href="{{ .RelPermalink }}">
{{ end }}

Setup​

Follow the steps below to transform CSS using any of the available PostCSS plugins.

Step 1 : Install Node.js.

Step 2 : Install the required Node.js packages in the root of your project. For example, to add vendor prefixes to your CSS rules:

npm i -D postcss postcss-cli autoprefixer

Step 3 : Create a PostCSS configuration file in the root of your project. You must name this file postcss.config.js or another supported file name. For example:

module.exports = {
  plugins: [
    require('autoprefixer')
  ]
};

Step 4 : Place your CSS file within the assets/css directory.

Step 5 : Process the resource with PostCSS:

{{ with resources.Get "css/main.css" | postCSS }}
  <link rel="stylesheet" href="{{ .RelPermalink }}">
{{ end }}

Options​

The css.PostCSS method takes an optional map of options.

config : (string) The directory that contains the PostCSS configuration file. Default is the root of the project directory.

noMap : (bool) Default is false. If true, disables inline sourcemaps.

inlineImports : (bool) Default is false. Enable inlining of @import statements. It does so recursively, but will only import a file once. URL imports (e.g. @import url('https://fonts.googleapis.com/css?family=Open+Sans&display=swap');) and imports with media queries will be ignored. Note that this import routine does not care about the CSS spec, so you can have @import anywhere in the file. Hugo will look for imports relative to the module mount and will respect theme overrides.

skipInlineImportsNotFound : (bool) Default is false. Before Hugo 0.99.0 when inlineImports was enabled and we failed to resolve an import, we logged it as a warning. We now fail the build. If you have regular CSS imports in your CSS that you want to preserve, you can either use imports with URL or media queries (Hugo does not try to resolve those) or set skipInlineImportsNotFound to true.

{{ $opts := dict "config" "config-directory" "noMap" true }}
{{ with resources.Get "css/main.css" | postCSS $opts }}
  <link rel="stylesheet" href="{{ .RelPermalink }}">
{{ end }}

No configuration file​

To avoid using a PostCSS configuration file, you can specify a minimal configuration using the options map.

use : (string) A space-delimited list of PostCSS plugins to use.

parser : (string) A custom PostCSS parser.

stringifier : (string) A custom PostCSS stringifier.

syntax : (string) Custom postcss syntax.

{{ $opts := dict "use" "autoprefixer postcss-color-alpha" }}
{{ with resources.Get "css/main.css" | postCSS $opts }}
  <link rel="stylesheet" href="{{ .RelPermalink }}">
{{ end }}

Check environment​

The current Hugo environment name (set by --environment or in configuration or OS environment) is available in the Node context, which allows constructs like this:

const autoprefixer = require('autoprefixer');
const purgecss = require('@fullhuman/postcss-purgecss');
module.exports = {
  plugins: [
    autoprefixer,
    process.env.HUGO_ENVIRONMENT !== 'development' ? purgecss : null
  ]
}