tsdx.config.js

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

module.exports = {
  rollup(config, opts) {
    config.plugins = config.plugins.map(p =>
      p.name === "replace"
        ? replace({
            "process.env.NODE_ENV": JSON.stringify(opts.env),
            preventAssignment: true,
          })
        : p,
    );
    return config;
  },
};