also transform 'core-js'

experimental/babel-preset-env/README.md

@@ -126,6 +126,9 @@ Defaults to `false`.
 
 A way to apply `babel-preset-env` for polyfills (via "babel-polyfill").
 
+> NOTE: This does not currently polyfill experimental/stage-x built-ins like the regular "babel-polyfill" does.
+> This will only work with npm >= 3 (which should be used with Babel 6 anyway)
+
 ```
 npm install babel-polyfill --save
 ```
@@ -151,6 +154,12 @@ import "core-js/modules/es6.symbol.species";
 import "core-js/modules/es6.array.from";
 ```
 
+> This will also work for "core-js" directly (`import "core-js";`)
+
+```
+npm install core-js --save
+```
+
 ---
 
 ## Examples

experimental/babel-preset-env/src/transformPolyfillRequirePlugin.js

@@ -1,4 +1,6 @@
-const polyfillSource = "babel-polyfill";
+function isPolyfillSource(value) {
+  return value === "babel-polyfill" || value === "core-js";
+}
 
 export default function ({ types: t }) {
   function createImportDeclaration(polyfill) {
@@ -18,20 +20,20 @@ export default function ({ types: t }) {
     );
   }
 
-  function isRequire(path, source) {
+  function isRequire(path) {
     return t.isExpressionStatement(path.node) &&
       t.isCallExpression(path.node.expression) &&
       t.isIdentifier(path.node.expression.callee) &&
       path.node.expression.callee.name === "require" &&
       path.node.expression.arguments.length === 1 &&
       t.isStringLiteral(path.node.expression.arguments[0]) &&
-      path.node.expression.arguments[0].value === source;
+      isPolyfillSource(path.node.expression.arguments[0].value);
   }
 
   const isPolyfillImport = {
     ImportDeclaration(path, state) {
       if (path.node.specifiers.length === 0 &&
-          path.node.source.value === polyfillSource) {
+          isPolyfillSource(path.node.source.value)) {
         this.numPolyfillImports++;
         if (this.numPolyfillImports > 1) {
           path.remove();
@@ -53,7 +55,7 @@ to the "transform-polyfill-require" plugin
 `);
       }
       path.get("body").forEach((bodyPath) => {
-        if (isRequire(bodyPath, polyfillSource)) {
+        if (isRequire(bodyPath)) {
           this.numPolyfillImports++;
           if (this.numPolyfillImports > 1) {
             path.remove();

experimental/babel-preset-env/test/fixtures/preset-options/core-js/actual.js

@@ -0,0 +1 @@
+import "core-js";

experimental/babel-preset-env/test/fixtures/preset-options/core-js/expected.js

@@ -0,0 +1,2 @@
+import "core-js/modules/es7.string.pad-start";
+import "core-js/modules/es7.string.pad-end";

experimental/babel-preset-env/test/fixtures/preset-options/core-js/options.json

@@ -0,0 +1,11 @@
+{
+  "presets": [
+    ["../../../../lib", {
+      "targets": {
+        "chrome": 55
+      },
+      "modules": false,
+      "useBuiltIns": true
+    }]
+  ]
+}

experimental/babel-preset-env/test/fixtures/preset-options/no-transform/actual.js

@@ -0,0 +1,2 @@
+import "not-core-js";
+import "not-babel-polyfill";

experimental/babel-preset-env/test/fixtures/preset-options/no-transform/expected.js

@@ -0,0 +1,2 @@
+import "not-core-js";
+import "not-babel-polyfill";

experimental/babel-preset-env/test/fixtures/preset-options/no-transform/options.json

@@ -0,0 +1,11 @@
+{
+  "presets": [
+    ["../../../../lib", {
+      "targets": {
+        "chrome": 55
+      },
+      "modules": false,
+      "useBuiltIns": true
+    }]
+  ]
+}