rollup.config.mjs

import { defineConfig } from "rollup";
import copy from "rollup-plugin-copy";
import { extname } from "node:path";

let destination = "node_modules/dataclass";

export default defineConfig({
  input: ["modules/Data.js", "modules/runtime.js"],
  output: [
    {
      dir: destination,
      format: "cjs",
      entryFileNames: ({ name }) => (name === "Data" ? "dataclass.js" : "[name].js"),
    },
    {
      dir: destination,
      format: "esm",
      entryFileNames: ({ name }) => (name === "Data" ? "dataclass.module.js" : "[name].module.js"),
    },
  ],
  plugins: [
    copy({
      targets: [
        { src: ["typings/*", "LICENSE"], dest: destination },
        {
          src: "typings/*",
          dest: destination,
          rename: (name, extension) =>
            name.endsWith(".d") || name.endsWith(".js")
              ? `${name.slice(0, name.lastIndexOf("."))}.module${extname(name)}.${extension}`
              : `${name}.module.${extension}`,
        },
        { src: "README.md", dest: destination, transform: generateReadme },
        { src: "package.json", dest: destination, transform: generatePkg },
      ],
    }),
  ],
});

function generatePkg(contents) {
  let pkg = JSON.parse(contents.toString());
  return JSON.stringify(
    {
      name: pkg.name,
      version: pkg.version,
      description: pkg.description,
      author: pkg.author,
      license: pkg.license,
      homepage: pkg.homepage,
      repository: pkg.repository,
      main: pkg.main,
      module: pkg.module,
      exports: {
        ".": "./dataclass.module.js",
        "./runtime": "./runtime.module.js",
      },
      types: pkg.types,
      sideEffects: pkg.sideEffects,
      files: pkg.files,
      keywords: pkg.keywords,
    },
    null,
    2,
  );
}

function generateReadme() {
  return `
The library brings flexibility and usefulness of data classes from Kotlin, Scala, or Python to TypeScript and JavaScript.

Read full docs [on the homepage](https://dataclass.js.org).

\`\`\`javascript
import { Data } from "dataclass";

// 1. easily describe your data classes using just language features
class User extends Data {
  name: string = "Anon";
  age: number = 0;
}

// 2. instantiate classes while type systems ensure correctness
let user = User.create({ name: "Liza", age: 23 });
// > User { name: "Liza", age: 23 }

// 3. make changes while benefiting from immutable values
let updated = user.copy({ name: "Ann" });
// > User { name: "Ann", age: 23 }
updated = updated.copy({ name: "Liza" });
// > User { name: "Liza", age: 23 }

// 4. compare objects by their value, not reference
console.log(user === updated, user.equals(updated));
// > false, true
\`\`\`
`.trimStart();
}