tsdx.config.js

const replace = require("@rollup/plugin-replace");
const postcss = require("rollup-plugin-postcss");
const autoprefixer = require("autoprefixer");
const cssnano = require("cssnano");

module.exports = {
  rollup(config, options) {
    config.plugins.push(
      postcss({
        plugins: [
          autoprefixer(),
          cssnano({
            preset: "default",
          }),
        ],
        // only write out CSS for the first bundle (avoids pointless extra files):
        extract: !!options.writeMeta,
      }),
    );
    config.plugins = config.plugins.map((p) =>
      p.name === "replace"
        ? replace({
            "process.env.NODE_ENV": JSON.stringify(options.env),
            preventAssignment: true,
          })
        : p,
    );
    return config; // always return a config.
  },
};