Use postcss to process your css with a large selection of plug-ins.

ember install ember-cli-postcss

The add-on can be used in two ways:

• on individual files, referred to as “compile”
• on all CSS files, referred to as “filter”

Note: it’s possible to use both compile and filter.

This step will look for either app.css or <project-name>.css in your styles directory. Additional files to be processed can be defined in the output paths configuration object for your application:

const app = new EmberApp(defaults, {
  outputPaths: {
    app: {
      html: 'index.html',
      css: {
        'app': '/assets/app.css',
        'print': '/assets/print.css'
      }
    }
  }
}

This step will run at the end of the build process on all CSS files, including the merged vendor.css file and any CSS imported into the Broccoli tree by add-ons.

Files can be white-listed and/or black-listed by using the respective include and exclude options. Each accepts an array of file globs, which are then passed on to Broccoli Funnel. An example can be seen in the sample configuration below.

There are two steps to setting up postcss with ember-cli-postcss:

1. install and require the node modules for any plug-ins
2. provide the node module and plug-in options as a postcssOptions object in ember-cli-build.js

The postcssOptions object should have a “compile” and/or “filter” property, which will have the properties enabled and plugins, which is an array of objects that contain a module property and an options property:

Some postcss plug-ins, like autoprefixer, allow you to configure which browsers to target for transpilation. When using Ember CLI >= 2.13.0, the browser targets configuration found in the file config/targets.js will be added to each plug-in’s options (as options.browsers). This browser list can be overwritten on a plug-in by plug-in basis. You can learn more about the targets feature on the Ember.js blog.

postcssOptions: {
  compile: {
    enabled: true, // defaults to true
    browsers: ['last 3 versions'], // this will override config found in config/targets.js
    plugins: [
      {
        module: <module>,
        options: {
          ...
        }
      }
    ]
  },
  filter: {
    enabled: true, // defaults to false
    map: false, // defaults to inline, false in production
    browsers: ['last 3 versions'], // this will override config found in config/targets.js
    include: ['styles/*.css'],
    exclude: ['vendor/bootstrap/**/*'],
    plugins: [
      {
        module: <module>,
        options: {
          ...
        }
      }
    ]
  }
}

Install the autoprefixer plug-in:

npm i --save-dev autoprefixer

Specify some plug-ins in your ember-cli-build.js:

const EmberApp = require('ember-cli/lib/broccoli/ember-app');
const autoprefixer = require('autoprefixer');

module.exports = function (defaults) {
  const app = new EmberApp(defaults, {
    postcssOptions: {
      compile: {
        enabled: false,
        browsers: ['last 3 versions'], // this will override config found in config/targets.js
      },
      filter: {
        enabled: true,
        plugins: [
          {
            module: autoprefixer,
            options: {
              browsers: ['last 2 versions'] // this will override the config, but just for this plugin
            }
          }
        ]
      }
    }
  });
  return app.toTree();
};