rollup.config.js

import path from 'path';
import ts from 'rollup-plugin-typescript2';
import json from '@rollup/plugin-json';

const pkgJson = require('./package.json');

// ensure TS checks only once for each build
let hasTSChecked = false;
const outputConfigs = {
  cjs: {
    file: path.resolve(__dirname, `dist/utils.cjs.js`),
    format: `cjs`
  }
};

const defaultFormats = ['cjs'];
const packageFormats = defaultFormats;
const packageConfigs = packageFormats.map(format => createConfig(format, outputConfigs[format]));

export default packageConfigs;

function createConfig(format, output, plugins = []) {
  if (!output) {
    console.log(require('chalk').yellow(`invalid format: "${format}"`));
    process.exit(1);
  }

  output.externalLiveBindings = false;

  const shouldEmitDeclarations = !hasTSChecked;

  const tsPlugin = ts({
    check: !hasTSChecked,
    tsconfig: path.resolve(__dirname, 'tsconfig.json'),
    tsconfigOverride: {
      compilerOptions: {
        declaration: shouldEmitDeclarations,
      },
      exclude: ['**/__tests__', 'test-dts'],
    },
  });
  // we only need to check TS and generate declarations once for each build.
  // it also seems to run into weird issues when checking multiple times
  // during a single build.
  hasTSChecked = true;

  // the browser builds of @vue/compiler-sfc requires postcss to be available
  // as a global (e.g. http://wzrd.in/standalone/postcss)
  const nodePlugins = [
    require('@rollup/plugin-node-resolve').nodeResolve({
      preferBuiltins: true
    }),
    require('@rollup/plugin-commonjs')({
      sourceMap: false,
    }),
  ];

  return {
    external: Object.keys(pkgJson.dependencies || {}),
    input: 'src/index.ts',
    plugins: [
      json({
        namedExports: false
      }),
      tsPlugin,
      ...nodePlugins,
      ...plugins
    ],
    output,
    onwarn: (msg, warn) => {
      if (!/Circular/.test(msg)) {
        warn(msg)
      }
    },
    treeshake: {
      moduleSideEffects: false
    }
  }
}