fix: Default export for duplicate names (babel#15736)

packages/babel-helper-split-export-declaration/src/index.ts

@@ -27,6 +27,8 @@ export default function splitExportDeclaration(
     const declaration = exportDeclaration.get("declaration");
     const standaloneDeclaration =
       declaration.isFunctionDeclaration() || declaration.isClassDeclaration();
+    const exportExpr =
+      declaration.isFunctionExpression() || declaration.isClassExpression();
 
     const scope = declaration.isScope()
       ? declaration.scope.parent
@@ -41,13 +43,13 @@ export default function splitExportDeclaration(
 
       id = scope.generateUidIdentifier("default");
 
-      if (
-        standaloneDeclaration ||
-        declaration.isFunctionExpression() ||
-        declaration.isClassExpression()
-      ) {
+      if (standaloneDeclaration || exportExpr) {
         declaration.node.id = cloneNode(id);
       }
+    } else if (exportExpr && scope.hasBinding(id.name)) {
+      needBindingRegistration = true;
+
+      id = scope.generateUidIdentifier(id.name);
     }
 
     const updatedDeclaration = standaloneDeclaration

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/export-expr-with-same-name/input.mjs

@@ -0,0 +1,4 @@
+import someFunction from './b';
+
+export default (function someFunction () {
+});

packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/export-expr-with-same-name/output.js

@@ -0,0 +1,10 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _b = _interopRequireDefault(require("./b"));
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+var _someFunction = function someFunction() {};
+exports.default = _someFunction;