rollup.config.js

import { readFileSync } from "fs";
import terser from "@rollup/plugin-terser";
import meta from "./package.json" assert { type: "json" };

// Extract copyrights from the LICENSE.
const copyright = readFileSync("./LICENSE", "utf-8")
  .split(/\n/g)
  .filter((line) => /^Copyright\s+/.test(line))
  .map((line) => line.replace(/^Copyright\s+/, ""))
  .join(", ");

const config = {
  input: "src/index.js",
  external: Object.keys(meta.dependencies || {}).filter((key) =>
    /^d3-/.test(key)
  ),
  output: {
    file: `dist/${meta.name}.js`,
    name: "d3",
    format: "umd",
    indent: false,
    extend: true,
    banner: `// ${meta.homepage} v${meta.version} Copyright ${copyright}`,
    globals: Object.assign(
      {},
      ...Object.keys(meta.dependencies || {})
        .filter((key) => /^d3-/.test(key))
        .map((key) => ({ [key]: "d3" }))
    ),
  },
  plugins: [],
};

export default [
  config,
  {
    ...config,
    output: {
      ...config.output,
      file: `dist/${meta.name}.min.js`,
    },
    plugins: [
      ...config.plugins,
      terser({
        output: {
          preamble: config.output.banner,
        },
      }),
    ],
  },
];