backport core-js-builder summary option, close #910

CHANGELOG.md

@@ -9,6 +9,7 @@
   - A bundle for Deno published on [deno.land/x/corejs](https://deno.land/x/corejs)
 - Updated Samsung Internet compat data mapping up to 15.0
 - Updated Opera Mobile compat data mapping up to 63
+- Added `summary` option to `core-js-builder`, see more info in the [`README`](https://github.com/zloirock/core-js/blob/master/packages/core-js-builder/README.md)
 
 ##### 3.15.2 - 2021.06.29
 - Worked around breakage related to `zone.js` loaded before `core-js`, [#953](https://github.com/zloirock/core-js/issues/953)

packages/core-js-builder/README.md

@@ -1,14 +1,16 @@
 For some cases could be useful to exclude some `core-js` features or generate a polyfill for target engines. This API helps conditionally include or exclude certain parts of [`core-js`](https://github.com/zloirock/core-js), use `browserslist` queries from [`core-js-compat`](https://github.com/zloirock/core-js/tree/master/packages/core-js-compat) package.
 
 ```js
-require('core-js-builder')({
-  modules: ['es', 'esnext.reflect', 'web'],         // modules / namespaces, by default - all `core-js` modules
-  exclude: ['es.math', 'es.number.constructor'],    // a blacklist of modules / namespaces, by default - empty list
-  targets: '> 0.5%',                                // optional browserslist query
-  filename: './my-core-js-bundle.js',               // optional target filename, if it's missed a file will not be created
-}).then(code => {                                   // code of result polyfill
-  // ...
-}).catch(error => {
-  // ...
+const builder = require('@core-js/builder');
+
+const bundle = await builder({
+  modules: ['es', 'esnext.reflect', 'web'],      // modules / namespaces, by default - all `core-js` modules
+  exclude: ['es.math', 'es.number.constructor'], // a blacklist of modules / namespaces, by default - empty list
+  targets: '> 0.5%, not dead, ie 9-11',          // optional browserslist or core-js-compat format query
+  summary: {                                     // shows summary for the bundle, disabled by default:
+    console: { size: true, modules: false },     // in the console, you could specify required parts or set `true` for enable all of them
+    comment: { size: false, modules: true },     // in the comment in the target file, similarly to `summary.console`
+  },
+  filename: './my-core-js-bundle.js',            // optional target filename, if it's missed a file will not be created
 });
 ```

packages/core-js-builder/index.js

@@ -14,14 +14,31 @@ const compat = require('core-js-compat/compat');
 const modulesList = require('core-js-compat/modules');
 const { banner } = require('./config');
 
+function normalizeSummary(unit = {}) {
+  let size, modules;
+  if (typeof unit !== 'object') {
+    size = modules = !!unit;
+  } else {
+    size = !!unit.size;
+    modules = !!unit.modules;
+  } return { size, modules };
+}
+
 module.exports = async function ({
   blacklist, // TODO: Remove from `core-js@4`
   exclude = [],
   modules = modulesList.slice(),
   targets,
   filename,
+  summary = {},
 } = {}) {
+  summary = { comment: normalizeSummary(summary.comment), console: normalizeSummary(summary.console) };
+
+  const TITLE = filename != null ? filename : '`core-js`';
   const set = new Set();
+  let script = banner;
+  let code = '';
+  let modulesWithTargets;
 
   function filter(method, list) {
     for (const ns of list) {
@@ -40,9 +57,11 @@ module.exports = async function ({
   // eslint-disable-next-line sonarjs/no-empty-collection -- false positive
   modules = modulesList.filter(it => set.has(it));
 
-  if (targets) modules = compat({ targets, filter: modules }).list;
-
-  let script = banner;
+  if (targets) {
+    const compatResult = compat({ targets, filter: modules });
+    modules = compatResult.list;
+    modulesWithTargets = compatResult.targets;
+  }
 
   if (modules.length) {
     const tempFileName = `core-js-${ Math.random().toString(36).slice(2) }.js`;
@@ -66,12 +85,30 @@ module.exports = async function ({
 
     await unlink(tempFile);
 
-    script += `\n!function (undefined) { 'use strict'; ${
+    code = `!function (undefined) { 'use strict'; ${
       // compress `__webpack_require__` with `keep_fnames` option
       String(file).replace(/function __webpack_require__/, 'var __webpack_require__ = function ')
     } }();`;
   }
 
+  if (summary.comment.size) script += `/*\n * size: ${ (code.length / 1024).toFixed(2) }KB w/o comments\n */`;
+  if (summary.comment.modules) script += `/*\n * modules list:\n${ modules.map(it => ` * ${ it }\n`).join('') } */`;
+  if (code) script += `\n${ code }`;
+
+  if (summary.console.size) {
+    // eslint-disable-next-line no-console -- output
+    console.log(`\u001B[32mbundling \u001B[36m${ TITLE }\u001B[32m, size: \u001B[36m${
+      (script.length / 1024).toFixed(2)
+    }KB\u001B[0m`);
+  }
+
+  if (summary.console.modules) {
+    // eslint-disable-next-line no-console -- output
+    console.log(`\u001B[32mbundling \u001B[36m${ TITLE }\u001B[32m, modules:\u001B[0m`);
+    // eslint-disable-next-line no-console -- output
+    console.log(JSON.stringify(modulesWithTargets || modules, null, '  '));
+  }
+
   if (typeof filename != 'undefined') {
     await mkdirp(dirname(filename));
     await writeFile(filename, script);