From 5c3645bca30758f07bd4abcb004ae4598d3966c7 Mon Sep 17 00:00:00 2001
From: Dunqing <29533304+Dunqing@users.noreply.github.com>
Date: Wed, 17 Sep 2025 09:46:51 +0000
Subject: [PATCH] fix(formatter): handle decorators correctly for class
 expressions in export (#13845)

The decorators of class expressions should be printed on the class expression itself; otherwise, the parentheses wouldn't wrap the decorators, which would cause a syntax error.

Input:
```ts
export default (@dec class {}) {};
```
Output before:
```ts
export default @dec (
  class {}
) { }
```
Output after:
```ts
export default (@dec class {}) {}
---
 crates/oxc_formatter/src/write/class.rs               | 10 ++++++----
 crates/oxc_formatter/src/write/export_declarations.rs |  1 +
 tasks/coverage/snapshots/formatter_typescript.snap    |  6 +-----
 3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/crates/oxc_formatter/src/write/class.rs b/crates/oxc_formatter/src/write/class.rs
index 830b41ea16e81..e4a9887d2ca9b 100644
--- a/crates/oxc_formatter/src/write/class.rs
+++ b/crates/oxc_formatter/src/write/class.rs
@@ -259,10 +259,12 @@ impl<'a> Format<'a> for FormatClass<'a, '_> {
         // Decorators are handled differently depending on the parent context
         // When the class is exported, the export statement handles decorator formatting
         // to ensure proper placement relative to the export keyword
-        if !matches!(
-            self.parent,
-            AstNodes::ExportNamedDeclaration(_) | AstNodes::ExportDefaultDeclaration(_)
-        ) {
+        if self.is_expression()
+            || !matches!(
+                self.parent,
+                AstNodes::ExportNamedDeclaration(_) | AstNodes::ExportDefaultDeclaration(_)
+            )
+        {
             write!(f, decorators)?;
         }
 
diff --git a/crates/oxc_formatter/src/write/export_declarations.rs b/crates/oxc_formatter/src/write/export_declarations.rs
index 2da6f208c99e5..24c25811f7615 100644
--- a/crates/oxc_formatter/src/write/export_declarations.rs
+++ b/crates/oxc_formatter/src/write/export_declarations.rs
@@ -33,6 +33,7 @@ fn format_export_keyword_with_class_decorators<'a>(
 
     if let AstNodes::Class(class) = declaration
         && !class.decorators.is_empty()
+        && !class.is_expression()
     {
         // `@decorator export class Cls {}`
         // decorators are placed before the export keyword
diff --git a/tasks/coverage/snapshots/formatter_typescript.snap b/tasks/coverage/snapshots/formatter_typescript.snap
index 0eb719daaf9f9..09b74d0b9fc1c 100644
--- a/tasks/coverage/snapshots/formatter_typescript.snap
+++ b/tasks/coverage/snapshots/formatter_typescript.snap
@@ -2,7 +2,7 @@ commit: 261630d6
 
 formatter_typescript Summary:
 AST Parsed     : 8816/8816 (100.00%)
-Positive Passed: 8785/8816 (99.65%)
+Positive Passed: 8787/8816 (99.67%)
 Mismatch: tasks/coverage/typescript/tests/cases/compiler/amdLikeInputDeclarationEmit.ts
 
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/arrayFromAsync.ts
@@ -45,10 +45,6 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/classes/prope
 Classes may not have a static property named prototypeClasses may not have a static property named prototypeClasses may not have a static property named prototypeClasses may not have a static property named prototypeClasses may not have a static property named prototypeClasses may not have a static property named prototype
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/controlFlow/controlFlowAssignmentPatternOrder.ts
 An implementation cannot be declared in ambient contexts.
-Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/esDecorators/classExpression/esDecorators-classExpression-missingEmitHelpers-classDecorator.3.ts
-Decorators are not valid here.Unexpected token
-Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/esDecorators/classExpression/namedEvaluation/esDecorators-classExpression-namedEvaluation.8.ts
-Decorators are not valid here.Unexpected token
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/expressions/elementAccess/letIdentifierInElementAccess01.ts
 Unexpected token
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/expressions/typeGuards/typeGuardsInRightOperandOfAndAndOperator.ts