Add useBuiltIns babel-preset-env option (fix #843) (#878)

Author: samsch

package.json

@@ -66,6 +66,7 @@
     "@vue/component-compiler-utils": "^1.0.0",
     "babel-cli": "^6.26.0",
     "babel-plugin-transform-async-super": "^1.0.0",
+    "babel-polyfill": "^6.26.0",
     "babel-register": "^6.26.0",
     "bsb-js": "^1.0.1",
     "codecov": "^3.0.0",

src/transforms/babel.js

@@ -217,7 +217,7 @@ function shouldIgnoreBabelrc(filename, babelrc) {
 async function getEnvConfig(asset, isSourceModule) {
   // Load the target engines for the app and generate a babel-preset-env config
   let targetEngines = await getTargetEngines(asset, true);
-  let targetEnv = await getEnvPlugins(targetEngines);
+  let targetEnv = await getEnvPlugins(targetEngines, true);
   if (!targetEnv) {
     return null;
   }
@@ -226,7 +226,7 @@ async function getEnvConfig(asset, isSourceModule) {
   // Otherwise, load the source engines and generate a babel-present-env config.
   if (asset.name.includes(NODE_MODULES) && !isSourceModule) {
     let sourceEngines = await getTargetEngines(asset, false);
-    let sourceEnv = (await getEnvPlugins(sourceEngines)) || targetEnv;
+    let sourceEnv = (await getEnvPlugins(sourceEngines, false)) || targetEnv;
 
     // Do a diff of the returned plugins. We only need to process the remaining plugins to get to the app target.
     let sourcePlugins = new Set(sourceEnv.map(p => p[0]));
@@ -240,7 +240,7 @@ async function getEnvConfig(asset, isSourceModule) {
 
 const envCache = new Map();
 
-async function getEnvPlugins(targets) {
+async function getEnvPlugins(targets, useBuiltIns = false) {
   if (!targets) {
     return null;
   }
@@ -250,7 +250,10 @@ async function getEnvPlugins(targets) {
     return envCache.get(key);
   }
 
-  let plugins = presetEnv.default({}, {targets, modules: false}).plugins;
+  let plugins = presetEnv.default(
+    {},
+    {targets, modules: false, useBuiltIns: useBuiltIns ? 'entry' : false}
+  ).plugins;
   envCache.set(key, plugins);
   return plugins;
 }

test/integration/babel-polyfill/.eslintrc.json

@@ -0,0 +1,6 @@
+{
+  "extends": "../.eslintrc.json",
+  "parserOptions": {
+    "sourceType": "module"
+  }
+}

test/integration/babel-polyfill/index.js

@@ -0,0 +1,3 @@
+import 'babel-polyfill';
+
+export async function Bar() {}

test/integration/babel-polyfill/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "parcel-test-babel-polyfill-browserslist",
+  "browserslist": ["last 2 Chrome versions"]
+}

test/javascript.js

@@ -628,6 +628,14 @@ describe('javascript', function() {
     assert(!file.includes('class Bar {}'));
   });
 
+  it('should support splitting babel-polyfill using browserlist', async function() {
+    await bundle(__dirname + '/integration/babel-polyfill/index.js');
+
+    let file = fs.readFileSync(__dirname + '/dist/index.js', 'utf8');
+    assert(file.includes('async function Bar() {}'));
+    assert(!file.includes('regenerator'));
+  });
+
   it('should support compiling with babel using browserslist for different environments', async function() {
     async function testBrowserListMultipleEnv(projectBasePath) {
       // Transpiled destructuring, like r = p.prop1, o = p.prop2, a = p.prop3;