rollup.config.js

import fs from "fs";
import path from "path";

import ts from "rollup-plugin-typescript2";
import MagicString from "magic-string";
import { transform } from "ts-transform-import-path-rewrite";

import pkg from "./package.json";

/** A hack to provide package.json files with "type": "commonjs" in cjs/umd subdirectories. */
function cjs() {
  return {
    name: "cjs",
    writeBundle({ dir, format }) {
      fs.writeFileSync(
        path.join(__dirname, dir, "package.json"),
        JSON.stringify(
          {
            name: `${pkg.name}-${format}`,
            type: "commonjs",
            private: true,
          },
          null,
          2,
        ),
      );
    },
  };
}

/** A hack to add triple-slash references to sibling d.ts files for deno. */
function dts() {
  return {
    name: "dts",
    renderChunk(code, info) {
      if (info.isEntry) {
        const dts = "./" + info.fileName.replace(/js$/, "d.ts");
        const ms = new MagicString(code);
        ms.prepend(`/// <reference types="${dts}" />\n`);
        code = ms.toString();
        const map = ms.generateMap({ hires: true });
        return { code, map };
      }

      return code;
    },
  };
}

/** A hack to rewrite import paths in d.ts files for deno. */
function transformer() {
  const rewritePath = transform({
    rewrite(importPath) {
      return importPath + ".js";
    },
  });

  return { afterDeclarations: [rewritePath] };
}

export default [
  {
    input: "./src/eventual.ts",
    output: {
      format: "esm",
      dir: "./",
      sourcemap: true,
      chunkFileNames: "dist/[hash].js",
    },
    plugins: [ts({ clean: true, transformers: [transformer] }), dts()],
  },
  {
    input: "./src/eventual.ts",
    output: {
      format: "cjs",
      dir: "cjs",
      sourcemap: true,
    },
    plugins: [ts(), cjs()],
  },
];