Handle as default in exports

Fixes #58

src/shared.js

@@ -459,10 +459,14 @@ function getSpecifierItems(tokens) {
     // If the last specifier has no trailing comma we end up here. Move all
     // trailing comments and whitespace from `.specifier` to `.after`, and
     // comments and whitespace that don’t belong to the specifier to
-    // `result.after`.
+    // `result.after`. The last non-comment and non-whitespace token is usually
+    // an identifier, but in this case it’s a keyword:
+    //
+    //    export { z, d as default } from "a"
     case "specifier": {
-      const lastIdentifierIndex = findLastIndex(current.specifier, (token2) =>
-        isIdentifier(token2)
+      const lastIdentifierIndex = findLastIndex(
+        current.specifier,
+        (token2) => isIdentifier(token2) || isKeyword(token2)
       );
 
       const specifier = current.specifier.slice(0, lastIdentifierIndex + 1);
@@ -767,6 +771,10 @@ function isIdentifier(node) {
   return node.type === "Identifier";
 }
 
+function isKeyword(node) {
+  return node.type === "Keyword";
+}
+
 function isPunctuator(node, value) {
   return node.type === "Punctuator" && node.value === value;
 }

test/exports.test.js

@@ -401,6 +401,28 @@ const baseTests = (expect) => ({
       errors: 1,
     },
 
+    // Handling `as default` (issue #58).
+    {
+      code: `export { something, something as default } from './something'`,
+      output: (actual) => {
+        expect(actual).toMatchInlineSnapshot(
+          `export { something as default,something } from './something'`
+        );
+      },
+      errors: 1,
+    },
+
+    // Tricky `default` cases.
+    {
+      code: `export {default as default, default as def, default as fault} from "b"`,
+      output: (actual) => {
+        expect(actual).toMatchInlineSnapshot(
+          `export {default as def, default as default, default as fault} from "b"`
+        );
+      },
+      errors: 1,
+    },
+
     // Test messageId, lines and columns.
     {
       code: input`