Set "sourceType" to "unambiguous" by default in Babel's options

.eslintrc.js

@@ -40,7 +40,7 @@ module.exports = {
         }],
         "no-console": "off",
         "valid-jsdoc": ["error", {"requireParamDescription": false, "requireReturnDescription": false}],
-        "node/no-unsupported-features": ["error", { version: 6 }],
+        "node/no-unsupported-features": ["error", { version: 8 }],
         "node/no-deprecated-api": "error",
         "node/no-missing-import": "error",
         "node/no-missing-require": [

fixtures/js/array_flat_commonjs.js

@@ -0,0 +1 @@
+module.exports = [[1, 2], [3, 4]].flat();

fixtures/js/array_flat_ecmascript.js

@@ -0,0 +1 @@
+export default [[1, 2], [3, 4]].flat();

fixtures/js/import_polyfills_commonjs.js

@@ -0,0 +1,3 @@
+const flattened = require('./array_flat_commonjs');
+
+document.getElementById('app').innerHTML = JSON.stringify(flattened);

fixtures/js/import_polyfills_ecmascript.js

@@ -0,0 +1,3 @@
+import flattened from './array_flat_ecmascript';
+
+document.getElementById('app').innerHTML = JSON.stringify(flattened);

lib/loaders/babel.js

@@ -25,7 +25,11 @@ module.exports = {
             // by some Babel presets/plugins (for instance the ones
             // that use browserslist)
             // https://github.com/babel/babel-loader#options
-            cacheDirectory: !webpackConfig.isProduction()
+            cacheDirectory: !webpackConfig.isProduction(),
+
+            // let Babel guess which kind of import/export syntax
+            // it should use based on the content of files
+            sourceType: 'unambiguous',
         };
 
         // configure babel (unless the user is specifying .babelrc)

package.json

@@ -63,11 +63,12 @@
     "babel-eslint": "^10.0.1",
     "chai": "^3.5.0",
     "chai-fs": "^1.0.0",
+    "core-js": "^3.0.0",
     "eslint": "^5.15.2",
     "eslint-loader": "^2.1.2",
     "eslint-plugin-header": "^1.0.0",
     "eslint-plugin-import": "^2.8.0",
-    "eslint-plugin-node": "^4.2.2",
+    "eslint-plugin-node": "^8.0.1",
     "fork-ts-checker-webpack-plugin": "^0.4.1",
     "handlebars": "^4.0.11",
     "handlebars-loader": "^1.7.0",

test/functional.js

@@ -1093,6 +1093,63 @@ module.exports = {
             });
         });
 
+        it('Babel adds polyfills correctly', (done) => {
+            const cwd = process.cwd();
+            after(() => {
+                process.chdir(cwd);
+            });
+
+            const appDir = testSetup.createTestAppDir();
+            process.chdir(appDir);
+
+            fs.writeFileSync(
+                path.join(appDir, 'package.json'),
+
+                // The test case uses Array.flat which
+                // isn't supported by IE11
+                '{"browserslist": "IE 11"}'
+            );
+
+            const config = createWebpackConfig('www/build', 'dev');
+            config.setPublicPath('/build');
+            config.addEntry('commonjs', './js/import_polyfills_commonjs.js');
+            config.addEntry('ecmascript', './js/import_polyfills_ecmascript.js');
+            config.configureBabel(null, {
+                useBuiltIns: 'usage',
+                corejs: 3,
+            });
+
+            testSetup.runWebpack(config, async (webpackAssert) => {
+                const checkPromises = [];
+
+                for (const scriptName of ['commonjs.js'/*, 'ecmascript.js'*/]) {
+                    // Check that the polyfills are included correctly
+                    // in both files.
+                    webpackAssert.assertOutputFileContains(
+                        scriptName,
+                        'Array.prototype.flat'
+                    );
+
+                    // Test that the generated scripts work fine
+                    await new Promise(resolve => {
+                        testSetup.requestTestPage(
+                            path.join(config.getContext(), 'www'),
+                            [
+                                'build/runtime.js',
+                                `build/${scriptName}`,
+                            ],
+                            (browser) => {
+                                browser.assert.text('body', '[1,2,3,4]');
+                                resolve();
+                            }
+                        );
+                    });
+                }
+
+                done();
+            });
+        });
+
         it('When enabled, react JSX is transformed!', (done) => {
             const config = createWebpackConfig('www/build', 'dev');
             config.setPublicPath('/build');

test/loaders/babel.js

@@ -45,7 +45,8 @@ describe('loaders/babel', () => {
         const actualLoaders = babelLoader.getLoaders(config);
         // we only add cacheDirectory
         expect(actualLoaders[0].options).to.deep.equal({
-            cacheDirectory: true
+            cacheDirectory: true,
+            sourceType: 'unambiguous',
         });
     });
 
@@ -57,7 +58,8 @@ describe('loaders/babel', () => {
         const actualLoaders = babelLoader.getLoaders(config);
         // cacheDirectory is disabled in production mode
         expect(actualLoaders[0].options).to.deep.equal({
-            cacheDirectory: false
+            cacheDirectory: false,
+            sourceType: 'unambiguous',
         });
     });
 

yarn.lock

@@ -2196,6 +2196,11 @@ core-js@^2.4.0:
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.5.tgz#44bc8d249e7fb2ff5d00e0341a7ffb94fbf67895"
   integrity sha512-klh/kDpwX8hryYL14M9w/xei6vrv6sE8gTHDG7/T/+SEovB/G4ejwcfE/CBzO6Edsu+OETZMZ3wcX/EjUkrl5A==
 
+core-js@^3.0.0:
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.0.1.tgz#1343182634298f7f38622f95e73f54e48ddf4738"
+  integrity sha512-sco40rF+2KlE0ROMvydjkrVMMG1vYilP2ALoRXcYR4obqbYIuV3Bg+51GEDW+HF8n7NRA+iaA4qD0nD9lo9mew==
+
 core-util-is@1.0.2, core-util-is@~1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/core-util-is/-/core-util-is-1.0.2.tgz#b5fd54220aa2bc5ab57aab7140c940754503c1a7"
@@ -3042,6 +3047,14 @@ eslint-module-utils@^2.3.0:
     debug "^2.6.8"
     pkg-dir "^2.0.0"
 
+eslint-plugin-es@^1.3.1:
+  version "1.4.0"
+  resolved "https://registry.yarnpkg.com/eslint-plugin-es/-/eslint-plugin-es-1.4.0.tgz#475f65bb20c993fc10e8c8fe77d1d60068072da6"
+  integrity sha512-XfFmgFdIUDgvaRAlaXUkxrRg5JSADoRC8IkKLc/cISeR3yHVMefFHQZpcyXXEUUPHfy5DwviBcrfqlyqEwlQVw==
+  dependencies:
+    eslint-utils "^1.3.0"
+    regexpp "^2.0.1"
+
 eslint-plugin-header@^1.0.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/eslint-plugin-header/-/eslint-plugin-header-1.2.0.tgz#f704779c6fbc7c668f180d835de1f462b0467c37"
@@ -3063,16 +3076,17 @@ eslint-plugin-import@^2.8.0:
     read-pkg-up "^2.0.0"
     resolve "^1.9.0"
 
-eslint-plugin-node@^4.2.2:
-  version "4.2.3"
-  resolved "https://registry.yarnpkg.com/eslint-plugin-node/-/eslint-plugin-node-4.2.3.tgz#c04390ab8dbcbb6887174023d6f3a72769e63b97"
-  integrity sha512-vIUQPuwbVYdz/CYnlTLsJrRy7iXHQjdEe5wz0XhhdTym3IInM/zZLlPf9nZ2mThsH0QcsieCOWs2vOeCy/22LQ==
+eslint-plugin-node@^8.0.1:
+  version "8.0.1"
+  resolved "https://registry.yarnpkg.com/eslint-plugin-node/-/eslint-plugin-node-8.0.1.tgz#55ae3560022863d141fa7a11799532340a685964"
+  integrity sha512-ZjOjbjEi6jd82rIpFSgagv4CHWzG9xsQAVp1ZPlhRnnYxcTgENUVBvhYmkQ7GvT1QFijUSo69RaiOJKhMu6i8w==
   dependencies:
-    ignore "^3.0.11"
-    minimatch "^3.0.2"
-    object-assign "^4.0.1"
-    resolve "^1.1.7"
-    semver "5.3.0"
+    eslint-plugin-es "^1.3.1"
+    eslint-utils "^1.3.1"
+    ignore "^5.0.2"
+    minimatch "^3.0.4"
+    resolve "^1.8.1"
+    semver "^5.5.0"
 
 eslint-scope@3.7.1:
   version "3.7.1"
@@ -3098,7 +3112,7 @@ eslint-scope@^4.0.3:
     esrecurse "^4.1.0"
     estraverse "^4.1.1"
 
-eslint-utils@^1.3.1:
+eslint-utils@^1.3.0, eslint-utils@^1.3.1:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/eslint-utils/-/eslint-utils-1.3.1.tgz#9a851ba89ee7c460346f97cf8939c7298827e512"
   integrity sha512-Z7YjnIldX+2XMcjr7ZkgEsOj/bREONV60qYeB/bjMAqqqZ4zxKyWX+BOUkdmRmA9riiIPVvo5x86m5elviOk0Q==
@@ -4192,16 +4206,16 @@ ignore-walk@^3.0.1:
   dependencies:
     minimatch "^3.0.4"
 
-ignore@^3.0.11:
-  version "3.3.10"
-  resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.10.tgz#0a97fb876986e8081c631160f8f9f389157f0043"
-  integrity sha512-Pgs951kaMm5GXP7MOvxERINe3gsaVjUWFm+UZPSq9xYriQAksyhg0csnS0KXSNRD5NmNdapXEpjxG49+AKh/ug==
-
 ignore@^4.0.6:
   version "4.0.6"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-4.0.6.tgz#750e3db5862087b4737ebac8207ffd1ef27b25fc"
   integrity sha512-cyFDKrqc/YdcWFniJhzI42+AzS+gNwmUzOSFcRCQYwySuBBBy/KjuxWLZ/FHEH6Moq1NizMOBWyTcv8O4OZIMg==
 
+ignore@^5.0.2:
+  version "5.0.6"
+  resolved "https://registry.yarnpkg.com/ignore/-/ignore-5.0.6.tgz#562dacc7ec27d672dde433aa683c543b24c17694"
+  integrity sha512-/+hp3kUf/Csa32ktIaj0OlRqQxrgs30n62M90UBpNd9k+ENEch5S+hmbW3DtcJGz3sYFTh4F3A6fQ0q7KWsp4w==
+
 image-size@~0.5.0:
   version "0.5.5"
   resolved "https://registry.yarnpkg.com/image-size/-/image-size-0.5.5.tgz#09dfd4ab9d20e29eb1c3e80b8990378df9e3cb9c"
@@ -7123,20 +7137,20 @@ resolve-url@^0.2.1:
   resolved "https://registry.yarnpkg.com/resolve-url/-/resolve-url-0.2.1.tgz#2c637fe77c893afd2a663fe21aa9080068e2052a"
   integrity sha1-LGN/53yJOv0qZj/iGqkIAGjiBSo=
 
-resolve@^1.1.7, resolve@^1.3.2:
-  version "1.8.1"
-  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.8.1.tgz#82f1ec19a423ac1fbd080b0bab06ba36e84a7a26"
-  integrity sha512-AicPrAC7Qu1JxPCZ9ZgCZlY35QgFnNqc+0LtbRNxnVw4TXvjQ72wnuL9JQcEBgXkI9JM8MsT9kaQoHcpCRJOYA==
-  dependencies:
-    path-parse "^1.0.5"
-
-resolve@^1.10.0, resolve@^1.5.0, resolve@^1.9.0:
+resolve@^1.10.0, resolve@^1.5.0, resolve@^1.8.1, resolve@^1.9.0:
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.10.0.tgz#3bdaaeaf45cc07f375656dfd2e54ed0810b101ba"
   integrity sha512-3sUr9aq5OfSg2S9pNtPA9hL1FVEAjvfOC4leW0SNf/mpnaakz2a9femSd6LqAww2RaFctwyf1lCqnTHuF1rxDg==
   dependencies:
     path-parse "^1.0.6"
 
+resolve@^1.3.2:
+  version "1.8.1"
+  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.8.1.tgz#82f1ec19a423ac1fbd080b0bab06ba36e84a7a26"
+  integrity sha512-AicPrAC7Qu1JxPCZ9ZgCZlY35QgFnNqc+0LtbRNxnVw4TXvjQ72wnuL9JQcEBgXkI9JM8MsT9kaQoHcpCRJOYA==
+  dependencies:
+    path-parse "^1.0.5"
+
 restore-cursor@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/restore-cursor/-/restore-cursor-2.0.0.tgz#9f7ee287f82fd326d4fd162923d62129eee0dfaf"
@@ -7318,11 +7332,6 @@ selfsigned@^1.9.1:
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.6.0.tgz#7e74256fbaa49c75aa7c7a205cc22799cac80004"
   integrity sha512-RS9R6R35NYgQn++fkDWaOmqGoj4Ek9gGs+DPxNUZKuwE183xjJroKvyo1IzVFeXvUrvmALy6FWD5xrdJT25gMg==
 
-semver@5.3.0, semver@~5.3.0:
-  version "5.3.0"
-  resolved "https://registry.yarnpkg.com/semver/-/semver-5.3.0.tgz#9b2ce5d3de02d17c6012ad326aa6b4d0cf54f94f"
-  integrity sha1-myzl094C0XxgEq0yaqa00M9U+U8=
-
 semver@^5.0.1, semver@^5.5.0:
   version "5.5.0"
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.5.0.tgz#dc4bbc7a6ca9d916dee5d43516f0092b58f7b8ab"
@@ -7333,6 +7342,11 @@ semver@^5.4.1:
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.5.1.tgz#7dfdd8814bdb7cabc7be0fb1d734cfb66c940477"
   integrity sha512-PqpAxfrEhlSUWge8dwIp4tZnQ25DIOthpiaHNIthsjEFQD6EvqUKUDM7L8O2rShkFccYo1VjJR0coWfNkCubRw==
 
+semver@~5.3.0:
+  version "5.3.0"
+  resolved "https://registry.yarnpkg.com/semver/-/semver-5.3.0.tgz#9b2ce5d3de02d17c6012ad326aa6b4d0cf54f94f"
+  integrity sha1-myzl094C0XxgEq0yaqa00M9U+U8=
+
 send@0.16.2:
   version "0.16.2"
   resolved "https://registry.yarnpkg.com/send/-/send-0.16.2.tgz#6ecca1e0f8c156d141597559848df64730a6bbc1"