Added 'intersect' support to esmodules targets (#1404)

CHANGELOG.md

@@ -2,6 +2,8 @@
 ##### Unreleased
 - Validation order of [`WeakMap.prototype.getOrInsertComputed`](https://github.com/tc39/proposal-upsert) updated following [proposal-upsert/79](https://github.com/tc39/proposal-upsert/pull/79) 
 - Don't call well-known Symbol methods for RegExp on primitive values [tc39/ecma262#3009](https://github.com/tc39/ecma262/pull/3009)
+- Added 'intersect' support for `targets.esmodules` (Babel v7 behavior)
+- Fixed handling of `targets.esmodules: true` (Babel v7 behavior)
 - Compat data improvements:
   - [Explicit Resource Management](https://github.com/tc39/proposal-explicit-resource-management) features disabled (again) in V8 ~ Chromium 135 and re-added in 136
   - [`RegExp.escape`](https://github.com/tc39/proposal-regex-escaping) marked as [shipped from V8 ~ Chromium 136](https://issues.chromium.org/issues/353856236#comment17)

packages/core-js-compat/README.md

@@ -96,7 +96,11 @@ console.log(targets);
   rhino: '1.7.13',        // Rhino engine version
   safari: '14.0',         // Safari version
   samsung: '14.0',        // Samsung Internet version
-  esmodules: true,        // That option set target to minimum supporting ES Modules versions of all browsers
+  /**
+   * true option set target to minimum supporting ES Modules versions of all browsers, ignoring `browsers` target.
+   * 'intersect' option intersects the `browsers` target and `browserslist`'s targets. The maximum version will be used.
+   */
+  esmodules: true | 'intersect',
   browsers: '> 0.25%',    // Browserslist query or object with target browsers
 });
 ```

packages/core-js-compat/compat.d.ts

@@ -12,7 +12,7 @@ type Environments = {
 
 type Targets = Environments & {
   browsers?: Environments | BrowserslistQuery,
-  esmodules?: boolean,
+  esmodules?: boolean | 'intersect',
 };
 
 type CompatOptions = {

packages/core-js-compat/targets-parser.js

@@ -53,14 +53,16 @@ module.exports = function (targets) {
 
   const list = Object.entries(rest);
 
-  if (browsers) {
+  const normalizedESModules = esmodules === 'intersect' ? 'intersect' : !!esmodules;
+
+  if (browsers && normalizedESModules !== true) {
     if (typeof browsers == 'string' || Array.isArray(browsers)) {
       list.push(...browserslist(browsers).map(it => it.split(' ')));
     } else {
       list.push(...Object.entries(browsers));
     }
   }
-  if (esmodules) {
+  if (normalizedESModules === true) {
     list.push(...Object.entries(external.modules));
   }
   if (node) {
@@ -81,12 +83,13 @@ module.exports = function (targets) {
     return a < b ? -1 : a > b ? 1 : 0;
   });
 
-  const reducedByMinVersion = new Map();
+  const reduced = new Map();
+  const operator = normalizedESModules === 'intersect' ? '>' : '<=';
   for (const [engine, version] of normalized) {
-    if (!reducedByMinVersion.has(engine) || compare(version, '<=', reducedByMinVersion.get(engine))) {
-      reducedByMinVersion.set(engine, version);
+    if (!reduced.has(engine) || compare(version, operator, reduced.get(engine))) {
+      reduced.set(engine, version);
     }
   }
 
-  return reducedByMinVersion;
+  return reduced;
 };

tests/compat-tools/targets-parser.mjs

@@ -89,7 +89,7 @@ deepEqual(targetsParser({
   ['chrome', '61'],
   ['chrome-android', '56'],
   ['deno', '1.0'],
-  ['edge', '13'],
+  ['edge', '16'],
   ['electron', '1'],
   ['firefox', '60'],
   ['firefox-android', '60'],
@@ -100,8 +100,17 @@ deepEqual(targetsParser({
   ['opera-android', '40'],
   ['quest', '4.0'],
   ['react-native', '0.70'],
-  ['safari', '5.1'],
+  ['safari', '10.1'],
   ['samsung', '4'],
 ]), 'mixed');
 
+deepEqual(targetsParser({
+  esmodules: 'intersect',
+  browsers: 'ie 11, chrome 56',
+  chrome: 77,
+}), new Map([
+  ['chrome', '77'],
+  ['ie', '11'],
+]), 'targets.esmodules: intersect');
+
 echo(chalk.green('targets parser tested'));