Resolve presets with named exports correctly (#4620)

packages/babel-core/src/transformation/file/options/option-manager.js

@@ -281,8 +281,20 @@ export default class OptionManager {
           val = require(presetLoc);
         }
 
-        // If the imported preset is a transpiled ES2015 module, grab the default export.
-        if (typeof val === "object" && val.__esModule) val = val.default;
+        // If the imported preset is a transpiled ES2015 module
+        if (typeof val === "object" && val.__esModule) {
+          // Try to grab the default export.
+          if (val.default) {
+            val = val.default;
+          } else {
+            // If there is no default export we treat all named exports as options
+            // and just remove the __esModule. This is to support presets that have been
+            // exporting named exports in the past, although we definitely want presets to
+            // only use the default export (with either an object or a function)
+            const { __esModule, ...rest } = val; // eslint-disable-line no-unused-vars
+            val = rest;
+          }
+        }
 
         // For compatibility with babel-core < 6.13.x, allow presets to export an object with a
         // a 'buildPreset' function that will return the preset itself, while still exporting a

packages/babel-core/test/fixtures/option-manager/presets/es2015_default.js

@@ -0,0 +1,12 @@
+// from code:
+// export default {
+//   plugins: [
+//     require('../../../../../babel-plugin-syntax-decorators'),
+//   ]
+// };
+'use strict';
+
+exports.__esModule = true;
+exports.default = {
+  plugins: [require('../../../../../babel-plugin-syntax-decorators')]
+};

packages/babel-core/test/fixtures/option-manager/presets/es2015_default_function.js

@@ -0,0 +1,17 @@
+// from code:
+// export default function() {
+//   return {
+//     plugins: [require('../../../../../babel-plugin-syntax-decorators'),]
+//   };
+// }
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+exports.default = function () {
+  return {
+    plugins: [require('../../../../../babel-plugin-syntax-decorators')]
+  };
+};

packages/babel-core/test/fixtures/option-manager/presets/es2015_default_object_function.js

@@ -0,0 +1,18 @@
+// from code:
+// export default {
+//   buildPreset: function() {
+//     return {
+//       plugins: [require('../../../../../babel-plugin-syntax-decorators'),]
+//     };
+//   }
+// }
+'use strict';
+
+exports.__esModule = true;
+exports.default = {
+  buildPreset: function buildPreset() {
+    return {
+      plugins: [require('../../../../../babel-plugin-syntax-decorators')]
+    };
+  }
+};

packages/babel-core/test/fixtures/option-manager/presets/es2015_function.js

@@ -0,0 +1,17 @@
+// from code:
+// export const buildPreset = function() {
+//   return {
+//     plugins: [require('../../../../../babel-plugin-syntax-decorators'),]
+//   };
+// }
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+var buildPreset = exports.buildPreset = function buildPreset() {
+  return {
+    plugins: [require('../../../../../babel-plugin-syntax-decorators')]
+  };
+};

packages/babel-core/test/fixtures/option-manager/presets/es2015_function_fallback.js

@@ -0,0 +1,50 @@
+// from code:
+// function preset() {
+//   return {
+//     plugins: [
+//       require('../../../../../babel-plugin-syntax-decorators'),
+//     ]
+//   };
+// }
+//
+// const oldConfig = preset();
+//
+// export default oldConfig;
+//
+// // However, for backward compatibility with babel-core < v6.13.x, we use the 'buildPreset'
+// // property of the preset object for the preset creation function with the enumerability
+// // caveat mentioned below.
+// Object.defineProperty(oldConfig, "buildPreset", {
+//   configurable: true,
+//   writable: true,
+//   // We make this non-enumerable so old versions of babel-core won't see it as an unknown property,
+//   // while allowing new versions to see it as a preset builder function.
+//   enumerable: false,
+//   value: preset,
+// });
+//
+
+"use strict";
+
+exports.__esModule = true;
+function preset() {
+  return {
+    plugins: [require('../../../../../babel-plugin-syntax-decorators')]
+  };
+}
+
+var oldConfig = preset();
+
+exports.default = oldConfig;
+
+// However, for backward compatibility with babel-core < v6.13.x, we use the 'buildPreset'
+// property of the preset object for the preset creation function with the enumerability
+// caveat mentioned below.
+Object.defineProperty(oldConfig, "buildPreset", {
+  configurable: true,
+  writable: true,
+  // We make this non-enumerable so old versions of babel-core won't see it as an unknown property,
+  // while allowing new versions to see it as a preset builder function.
+  enumerable: false,
+  value: preset
+});

packages/babel-core/test/fixtures/option-manager/presets/es2015_named.js

@@ -0,0 +1,8 @@
+// from code:
+// export const plugins = [
+//   require('../../../../../babel-plugin-syntax-decorators'),
+// ];
+'use strict';
+
+exports.__esModule = true;
+var plugins = exports.plugins = [require('../../../../../babel-plugin-syntax-decorators')];

packages/babel-core/test/fixtures/option-manager/presets/es5.js

@@ -0,0 +1,5 @@
+module.exports = {
+  plugins: [
+    require('../../../../../babel-plugin-syntax-decorators'),
+  ]
+};

packages/babel-core/test/fixtures/option-manager/presets/es5_function.js

@@ -0,0 +1,9 @@
+module.exports = {
+  buildPreset: function () {
+    return {
+      plugins: [
+        require('../../../../../babel-plugin-syntax-decorators'),
+      ]
+    };
+  }
+};

packages/babel-core/test/option-manager.js

@@ -31,7 +31,8 @@ suite("option-manager", function () {
         },
         /Unknown option: base.randomOption/
       );
-    })
+    });
+
     test("throws for removed babel 5 options", function() {
       return assert.throws(
         function () {
@@ -43,17 +44,42 @@ suite("option-manager", function () {
         },
         /Using removed Babel 5 option: base.auxiliaryComment - Use `auxiliaryCommentBefore` or `auxiliaryCommentAfter`/
       );
-    })
+    });
+
     test("throws for resolved but erroring preset", function() {
       return assert.throws(
         function () {
           var opt = new OptionManager(new Logger(null, "unknown"));
           opt.init({
-            'presets': [path.resolve(__dirname, "fixtures", "option-manager", "not-a-preset")]
+            'presets': [path.join(__dirname, "fixtures/option-manager/not-a-preset")]
           });
         },
         /While processing preset: .*option-manager(?:\/|\\\\)not-a-preset\.js/
       );
-    })
+    });
+  });
+
+  suite("presets", function () {
+    function presetTest(name) {
+      test(name, function () {
+        var opt = new OptionManager(new Logger(null, "unknown"));
+        var options = opt.init({
+          'presets': [path.join(__dirname, "fixtures/option-manager/presets", name)]
+        });
+
+        assert.equal(true, Array.isArray(options.plugins));
+        assert.equal(1, options.plugins.length);
+      });
+    }
+
+    presetTest('es5');
+    presetTest('es5_function');
+    presetTest('es2015_default');
+    presetTest('es2015_default_function');
+    presetTest('es2015_default_object_function');
+    presetTest('es2015_function');
+    presetTest('es2015_function_fallback');
+    presetTest('es2015_named');
+
   });
 });