How to split antd theme into smaller components

Recently I stumbled upon an interesting problem at work. I was using ant-design and I wanted to customize default theme variables. To do that I’ve created a theme.less:

@import "~antd/dist/antd.less";

@primary-color: #003dff;
@dark-color: #38b6ab;
@font-family: Inter;

Everything was fine until I looked into webpack-bundle-analyzer I saw that theme.less was taking a huge portion of the overall bundle size:

What is the problem here?

It turns out that by @import '~antd/dist/antd.less' I accidentally imported whole antd styles. Because of that theme.less is so big. How to fix it? After googling around I found out about 2 steps that I could that to lower size of my bundle:

• customize antd theme via webpack
• tell transpiler (babel) to inject css when you are using antd components

Customizing antd theme

How you can customize antd theme? According to antd docs you can add options to webpack less-loader:

// the rest of webpack config
module.exports = {
  module: {
    rules: [
      // the rest of loaders setup
      {
        test: /\.less$/,
        use: [
          {
            loader: "style-loader",
          },
          {
            loader: "css-loader",
          },
          {
            loader: "less-loader",
            options: {
              lessOptions: {
                modifyVars: {
                  // override antd default styles
                  "primary-color": "#003dff",
                  "dark-color": "#38b6ab",
                  "font-family": "Inter",
                },
                javascriptEnabled: true,
              },
            },
          },
        ],
      },
    ],
  },
};

Setup babel to inject CSS

The second optimization I added was to extract only those styles that are used by antd components inside my application via babel-plugin-import. You can see the recommended configuration of this plugin below:

{
  // rest of .babelrc
  "plugins": [
    [
      "import",
      {
        "libraryName": "antd",
        "style": true
      }
    ]
  ]
}

Summary & TL;DR

In this blog post, I wrote on how to override antd theme without importing whole library styles and how to use only those styles that are actually used in your application.