fix(cloudflare): Skip comments when locating the default keyword in the Vite transform

packages/cloudflare/src/vite/transform.ts

@@ -396,7 +396,7 @@ function wrapDefaultExport(node: ExportDefaultNode, ctx: TransformContext, state
   // MagicString positions are always relative to the original source. Only the `export default`
   // keywords are replaced, so parentheses around the expression stay.
   const source = state.ms.original;
-  const keywordsEnd = node.start + source.slice(node.start, decl.start).lastIndexOf('default') + 'default'.length;
+  const keywordsEnd = exportDefaultKeywordsEnd(source, node.start);
   const declaredName =
     decl.type === 'ClassDeclaration' || decl.type === 'FunctionDeclaration'
       ? (decl as ClassDeclarationNode).id?.name
@@ -425,6 +425,26 @@ function wrapDefaultExport(node: ExportDefaultNode, ctx: TransformContext, state
   state.autoWrapped.add(DEFAULT_EXPORT);
 }
 
+/**
+ * Offset just past the `default` keyword of the `export default` statement at `start`. Comments can
+ * sit between `export`, `default` and the expression, and may themselves contain the word `default`.
+ */
+function exportDefaultKeywordsEnd(source: string, start: number): number {
+  let index = start + 'export'.length;
+  while (index < source.length && !source.startsWith('default', index)) {
+    if (source.startsWith('//', index)) {
+      const lineEnd = source.indexOf('\n', index);
+      index = lineEnd === -1 ? source.length : lineEnd;
+    } else if (source.startsWith('/*', index)) {
+      const commentEnd = source.indexOf('*/', index + 2);
+      index = commentEnd === -1 ? source.length : commentEnd + 2;
+    } else {
+      index++;
+    }
+  }
+  return index + 'default'.length;
+}
+
 function isAnonymousFunctionOrClass(node: BaseNode): boolean {
   if (node.type === 'ArrowFunctionExpression') return true;
   const isFunctionOrClass = [

packages/cloudflare/test/vite/transform.test.ts

@@ -362,6 +362,33 @@ describe('default export wrapping', () => {
     );
   });
 
+  it('wraps a default export with a comment that mentions `default`', () => {
+    const code = 'export /* the default */ default /* default handler */ { fetch() {} };';
+
+    expect(transform(code, ctx)!.code).toBe(
+      [
+        "import * as __SENTRY__ from '@sentry/cloudflare';",
+        'var __SENTRY_DEFAULT_EXPORT__ = /* default handler */ { fetch() {} };',
+        'export { __SENTRY_DEFAULT_EXPORT__ as default };',
+        '__SENTRY_DEFAULT_EXPORT__ = __SENTRY__.withSentry((env) => ({}), __SENTRY_DEFAULT_EXPORT__);',
+      ].join('\n'),
+    );
+  });
+
+  it('wraps a default export with a line comment that mentions `default`', () => {
+    const code = ['export // the default', 'default // default handler', '{ fetch() {} };'].join('\n');
+
+    expect(transform(code, ctx)!.code).toBe(
+      [
+        "import * as __SENTRY__ from '@sentry/cloudflare';",
+        'var __SENTRY_DEFAULT_EXPORT__ = // default handler',
+        '{ fetch() {} };',
+        'export { __SENTRY_DEFAULT_EXPORT__ as default };',
+        '__SENTRY_DEFAULT_EXPORT__ = __SENTRY__.withSentry((env) => ({}), __SENTRY_DEFAULT_EXPORT__);',
+      ].join('\n'),
+    );
+  });
+
   it('keeps the module binding of a named default class', () => {
     const code = ['export default class Handler { fetch() {} }', 'Handler.ready = true;'].join('\n');