also import regenerator when the transform is required

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

@@ -184,7 +184,12 @@ export default function buildPreset(context, opts = {}) {
     }
   }
 
-  transformations = [...transformations, ...whitelist].map((pluginName) => {
+  let allTransformations = [...transformations, ...whitelist];
+  let regenerator = allTransformations.indexOf("transform-regenerator") >= 0;
+
+  console.log(allTransformations, regenerator);
+
+  let plugins = allTransformations.map((pluginName) => {
     return [require(`babel-plugin-${pluginName}`), { loose }];
   });
 
@@ -198,8 +203,8 @@ export default function buildPreset(context, opts = {}) {
   return {
     plugins: [
       ...modules,
-      ...transformations,
-      useBuiltIns === true && [transformPolyfillRequirePlugin, { polyfills }]
+      ...plugins,
+      useBuiltIns === true && [transformPolyfillRequirePlugin, { polyfills, regenerator }]
     ].filter(Boolean)
   };
 }

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

@@ -30,6 +30,25 @@ export default function ({ types: t }) {
       isPolyfillSource(path.node.expression.arguments[0].value);
   }
 
+  function createImport(polyfill, requireType) {
+    if (requireType === "import") {
+      return createImportDeclaration(polyfill);
+    } else {
+      return createRequireStatement(polyfill);
+    }
+  }
+
+  function createImports(polyfills, requireType, regenerator) {
+    let imports = polyfills
+    .filter((el, i, arr) => arr.indexOf(el) === i)
+    .map((polyfill) => createImport(polyfill, requireType));
+
+    return [
+      ...imports,
+      regenerator && createImport("regenerator-runtime/runtime", requireType)
+    ].filter(Boolean);
+  }
+
   const isPolyfillImport = {
     ImportDeclaration(path, state) {
       if (path.node.specifiers.length === 0 &&
@@ -40,10 +59,9 @@ export default function ({ types: t }) {
           return;
         }
 
-        let imports = state.opts.polyfills
-        .filter((el, i, arr) => arr.indexOf(el) === i)
-        .map((p) => createImportDeclaration(p));
-        path.replaceWithMultiple(imports);
+        path.replaceWithMultiple(
+          createImports(state.opts.polyfills, "import", state.opts.regenerator)
+        );
       }
     },
     Program(path, state) {
@@ -62,10 +80,9 @@ to the "transform-polyfill-require" plugin
             return;
           }
 
-          let requires = state.opts.polyfills
-          .filter((el, i, arr) => arr.indexOf(el) === i)
-          .map((p) => createRequireStatement(p));
-          bodyPath.replaceWithMultiple(requires);
+          bodyPath.replaceWithMultiple(
+            createImports(state.opts.polyfills, "require", state.opts.regenerator)
+          );
         }
       });
     }

experimental/babel-preset-env/test/fixtures/plugin-options/regenerator-false/actual.js

@@ -0,0 +1 @@
+import "babel-polyfill";

experimental/babel-preset-env/test/fixtures/plugin-options/regenerator-false/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    ["../../../../lib/transformPolyfillRequirePlugin", {
+      "regenerator": false,
+      "polyfills": []
+    }]
+  ]
+}

experimental/babel-preset-env/test/fixtures/plugin-options/regenerator-true/actual.js

@@ -0,0 +1 @@
+import "babel-polyfill";

experimental/babel-preset-env/test/fixtures/plugin-options/regenerator-true/expected.js

@@ -0,0 +1 @@
+import "core-js/modules/regenerator-runtime/runtime";

experimental/babel-preset-env/test/fixtures/plugin-options/regenerator-true/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    ["../../../../lib/transformPolyfillRequirePlugin", {
+      "regenerator": true,
+      "polyfills": []
+    }]
+  ]
+}

experimental/babel-preset-env/test/fixtures/preset-options/use-builtins-chrome-48/expected.js

@@ -28,5 +28,6 @@ import "core-js/modules/es7.object.entries";
 import "core-js/modules/es7.object.get-own-property-descriptors";
 import "core-js/modules/es7.string.pad-start";
 import "core-js/modules/es7.string.pad-end";
+import "core-js/modules/regenerator-runtime/runtime";
 
-Math.pow(1, 2);
+Math.pow(1, 2);

experimental/babel-preset-env/test/fixtures/preset-options/use-builtins-chrome-49/expected.js

@@ -14,5 +14,6 @@ import "core-js/modules/es7.object.entries";
 import "core-js/modules/es7.object.get-own-property-descriptors";
 import "core-js/modules/es7.string.pad-start";
 import "core-js/modules/es7.string.pad-end";
+import "core-js/modules/regenerator-runtime/runtime";
 
 Math.pow(1, 2);

experimental/babel-preset-env/test/fixtures/preset-options/use-builtins-regenerator-true/actual.js

@@ -0,0 +1,2 @@
+import "babel-polyfill";
+1 ** 2;

experimental/babel-preset-env/test/fixtures/preset-options/use-builtins-regenerator-true/expected.js

@@ -0,0 +1,86 @@
+import "core-js/modules/es6.typed.data-view";
+import "core-js/modules/es6.typed.int8-array";
+import "core-js/modules/es6.typed.uint8-array";
+import "core-js/modules/es6.typed.uint8-clamped-array";
+import "core-js/modules/es6.typed.int16-array";
+import "core-js/modules/es6.typed.uint16-array";
+import "core-js/modules/es6.typed.int32-array";
+import "core-js/modules/es6.typed.uint32-array";
+import "core-js/modules/es6.typed.float32-array";
+import "core-js/modules/es6.typed.float64-array";
+import "core-js/modules/es6.map";
+import "core-js/modules/es6.set";
+import "core-js/modules/es6.weak-map";
+import "core-js/modules/es6.weak-set";
+import "core-js/modules/es6.reflect.apply";
+import "core-js/modules/es6.reflect.construct";
+import "core-js/modules/es6.reflect.define-property";
+import "core-js/modules/es6.reflect.delete-property";
+import "core-js/modules/es6.reflect.get";
+import "core-js/modules/es6.reflect.get-own-property-descriptor";
+import "core-js/modules/es6.reflect.get-prototype-of";
+import "core-js/modules/es6.reflect.has";
+import "core-js/modules/es6.reflect.is-extensible";
+import "core-js/modules/es6.reflect.own-keys";
+import "core-js/modules/es6.reflect.prevent-extensions";
+import "core-js/modules/es6.reflect.set";
+import "core-js/modules/es6.reflect.set-prototype-of";
+import "core-js/modules/es6.promise";
+import "core-js/modules/es6.symbol";
+import "core-js/modules/es6.object.assign";
+import "core-js/modules/es6.object.is";
+import "core-js/modules/es6.object.get-own-property-symbols";
+import "core-js/modules/es6.object.set-prototype-of";
+import "core-js/modules/es6.function.name";
+import "core-js/modules/es6.string.raw";
+import "core-js/modules/es6.string.from-code-point";
+import "core-js/modules/es6.string.code-point-at";
+import "core-js/modules/es6.string.repeat";
+import "core-js/modules/es6.string.starts-with";
+import "core-js/modules/es6.string.ends-with";
+import "core-js/modules/es6.string.includes";
+import "core-js/modules/es6.regexp.flags";
+import "core-js/modules/es6.regexp.match";
+import "core-js/modules/es6.regexp.replace";
+import "core-js/modules/es6.regexp.split";
+import "core-js/modules/es6.regexp.search";
+import "core-js/modules/es6.array.from";
+import "core-js/modules/es6.array.of";
+import "core-js/modules/es6.array.copy-within";
+import "core-js/modules/es6.array.find";
+import "core-js/modules/es6.array.find-index";
+import "core-js/modules/es6.array.fill";
+import "core-js/modules/es6.array.iterator";
+import "core-js/modules/es6.number.is-finite";
+import "core-js/modules/es6.number.is-integer";
+import "core-js/modules/es6.number.is-safe-integer";
+import "core-js/modules/es6.number.is-nan";
+import "core-js/modules/es6.number.epsilon";
+import "core-js/modules/es6.number.min-safe-integer";
+import "core-js/modules/es6.number.max-safe-integer";
+import "core-js/modules/es6.math.acosh";
+import "core-js/modules/es6.math.asinh";
+import "core-js/modules/es6.math.atanh";
+import "core-js/modules/es6.math.cbrt";
+import "core-js/modules/es6.math.clz32";
+import "core-js/modules/es6.math.cosh";
+import "core-js/modules/es6.math.expm1";
+import "core-js/modules/es6.math.fround";
+import "core-js/modules/es6.math.hypot";
+import "core-js/modules/es6.math.imul";
+import "core-js/modules/es6.math.log1p";
+import "core-js/modules/es6.math.log10";
+import "core-js/modules/es6.math.log2";
+import "core-js/modules/es6.math.sign";
+import "core-js/modules/es6.math.sinh";
+import "core-js/modules/es6.math.tanh";
+import "core-js/modules/es6.math.trunc";
+import "core-js/modules/es7.array.includes.js";
+import "core-js/modules/es7.object.values";
+import "core-js/modules/es7.object.entries";
+import "core-js/modules/es7.object.get-own-property-descriptors";
+import "core-js/modules/es7.string.pad-start";
+import "core-js/modules/es7.string.pad-end";
+import "core-js/modules/regenerator-runtime/runtime";
+
+Math.pow(1, 2);

experimental/babel-preset-env/test/fixtures/preset-options/use-builtins-regenerator-true/options.json

@@ -0,0 +1,8 @@
+{
+  "presets": [
+    ["../../../../lib", {
+      "modules": false,
+      "useBuiltIns": true
+    }]
+  ]
+}