package: Add polyfill and minification (#11)

Author: microbit-carlos

config/global.d.ts

@@ -53,10 +53,17 @@ declare module 'rollup-plugin-terser' {
 declare module 'rollup-plugin-babel' {
   export interface Options {
     presets?: string | (string | object)[][];
+    sourceType?: string;
+    ignore?: RegExp[];
   }
   const plugin: RollupPluginImpl<Options>;
   export default plugin;
 }
+declare module 'rollup-plugin-babel-minify' {
+  export interface Options {}
+  const plugin: RollupPluginImpl<Options>;
+  export default plugin;
+}
 
 // =====================∫
 // missing library types

config/rollup.config.js

@@ -4,6 +4,7 @@ import nodeResolve from 'rollup-plugin-node-resolve';
 import json from 'rollup-plugin-json';
 import commonjs from 'rollup-plugin-commonjs';
 import babel from 'rollup-plugin-babel';
+import minify from 'rollup-plugin-babel-minify';
 
 import pkg from '../package.json';
 
@@ -27,7 +28,7 @@ const external = Object.keys(pkg.peerDependencies) || [];
 /**
  *  @type {Plugin[]}
  */
-const plugins = /** @type {Plugin[]} */ ([
+const defaultPlugins = /** @type {Plugin[]} */ ([
   json(),
   commonjs(),
   // Allow node_modules resolution.  Use 'external' to control
@@ -42,30 +43,64 @@ const plugins = /** @type {Plugin[]} */ ([
         {
           // Transformation of ES6 module syntax to another module type
           modules: false,
+          // How to handle polyfills, 'usage' analyses each file and places the
+          // required imports on each one, rollup ensures single imports
+          useBuiltIns: 'usage',
           targets: {
-            ie: '10',
+            // To check what's covered: https://browserl.ist
+            browsers: [
+              '>0.1%',
+              'ie>=10',
+              'not ie<10',
+              'not ios_saf<9',
+              'not android<5',
+            ],
           },
         },
       ],
     ],
+    // To avoiding circular dependencies with useBuiltIns: 'usage' these two
+    // settings are needed, which avoids core-js importing itself
+    sourceType: 'unambiguous',
+    ignore: [/\/core-js/],
   }),
 ]);
 
 /**
- * @type {Config}
+ * @param {{outputFile: string, extraPlugins?: Plugin[]}} options
  */
-const umdConfig = {
+const createUmdConfig = ({ outputFile, extraPlugins }) => ({
   inlineDynamicImports: true,
   external,
   // Start with esm5 (es5 with import/export)
   input: resolve(dist, 'esm5', 'index.js'),
   output: {
-    file: pkg.main,
+    file: outputFile,
     format: 'umd',
     name: pkg.config.umdName,
     sourcemap: true,
   },
-  plugins,
-};
+  plugins: [...defaultPlugins, ...(extraPlugins || [])],
+});
 
-export default [umdConfig];
+/**
+ * @type object
+ */
+const umdConfig = createUmdConfig({
+  outputFile: pkg.main,
+});
+
+/**
+ * @type object
+ */
+const umdConfigMin = createUmdConfig({
+  outputFile: pkg.mainMin,
+  extraPlugins: [
+    minify({
+      comments: false,
+      sourceMap: true,
+    }),
+  ],
+});
+
+export default [umdConfig, umdConfigMin];