rollupLicensePlugin.ts

import fs from "node:fs";
import license from "rollup-plugin-license";
import colors from "picocolors";
import type { Plugin } from "rollup";

export default function licensePlugin(
  licenseFilePath: string,
  licenseTitle: string,
  packageName: string
): Plugin {
  return license({
    thirdParty(dependencies) {
      // https://github.com/rollup/rollup/blob/master/build-plugins/generate-license-file.js
      // MIT Licensed https://github.com/rollup/rollup/blob/master/LICENSE-CORE.md
      const coreLicense = fs.readFileSync(
        new URL("./LICENSE", import.meta.url)
      );
      function sortLicenses(licenses: Set<string>) {
        let withParenthesis: string[] = [];
        let noParenthesis: string[] = [];
        licenses.forEach((license) => {
          if (/^\(/.test(license)) {
            withParenthesis.push(license);
          } else {
            noParenthesis.push(license);
          }
        });
        withParenthesis = withParenthesis.sort();
        noParenthesis = noParenthesis.sort();
        return [...noParenthesis, ...withParenthesis];
      }
      const licenses = new Set<string>();
      const dependencyLicenseTexts = dependencies
        .sort(({ name: nameA }, { name: nameB }) => {
          return nameA! > nameB! ? 1 : nameB! > nameA! ? -1 : 0;
        })
        .map(
          ({
            name,
            license,
            licenseText,
            author,
            maintainers,
            contributors,
            repository,
          }) => {
            let text = `## ${name}\n`;
            if (license) {
              text += `License: ${license}\n`;
            }
            const names = new Set();
            for (const person of [author, ...maintainers, ...contributors]) {
              const name = typeof person === "string" ? person : person?.name;
              if (name) {
                names.add(name);
              }
            }
            if (names.size > 0) {
              text += `By: ${Array.from(names).join(", ")}\n`;
            }
            if (repository) {
              text += `Repository: ${
                typeof repository === "string" ? repository : repository.url
              }\n`;
            }
            if (licenseText) {
              text +=
                "\n" +
                licenseText
                  .trim()
                  .replace(/(\r\n|\r)/g, "\n")
                  .split("\n")
                  .map((line) => `> ${line}`)
                  .join("\n") +
                "\n";
            }
            licenses.add(license!);
            return text;
          }
        )
        .join("\n---------------------------------------\n\n");
      const licenseText =
        `# ${licenseTitle}\n` +
        `${packageName} is released under the MIT license:\n\n` +
        coreLicense +
        `\n# Licenses of bundled dependencies\n` +
        `The published ${packageName} artifact additionally contains code with the following licenses:\n` +
        `${sortLicenses(licenses).join(", ")}\n\n` +
        `# Bundled dependencies:\n` +
        dependencyLicenseTexts;
      const existingLicenseText = fs.readFileSync(licenseFilePath, "utf8");
      if (existingLicenseText !== licenseText) {
        fs.writeFileSync(licenseFilePath, licenseText);
        console.warn(
          colors.yellow(
            "\nLICENSE.md updated. You should commit the updated file.\n"
          )
        );
      }
    },
  });
}