From 536ede838be90581cdc37380b518c47884b6c2b6 Mon Sep 17 00:00:00 2001
From: Boshen <boshenc@gmail.com>
Date: Mon, 3 Mar 2025 22:26:06 +0800
Subject: [PATCH] fix(parser): parse `@__NO_SIDE_EFFECTS` between `export
 default` and `async function`

---
 crates/oxc_codegen/src/gen.rs                        |  1 +
 .../oxc_codegen/tests/integration/pure_comments.rs   |  2 ++
 .../tests/integration/snapshots/pure_comments.snap   |  6 ++++++
 crates/oxc_parser/src/js/module.rs                   | 12 +++++++++---
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/crates/oxc_codegen/src/gen.rs b/crates/oxc_codegen/src/gen.rs
index 128450e39f151..0c57bea42b096 100644
--- a/crates/oxc_codegen/src/gen.rs
+++ b/crates/oxc_codegen/src/gen.rs
@@ -221,6 +221,7 @@ impl Gen for Statement<'_> {
             Self::FunctionDeclaration(decl) => {
                 p.print_statement_comments(decl.span.start);
                 if decl.pure && p.options.print_annotation_comments() {
+                    p.print_indent();
                     p.print_str(NO_SIDE_EFFECTS_NEW_LINE_COMMENT);
                 }
                 p.print_indent();
diff --git a/crates/oxc_codegen/tests/integration/pure_comments.rs b/crates/oxc_codegen/tests/integration/pure_comments.rs
index 9a28a7277873f..89b81e846e626 100644
--- a/crates/oxc_codegen/tests/integration/pure_comments.rs
+++ b/crates/oxc_codegen/tests/integration/pure_comments.rs
@@ -61,6 +61,8 @@ async function* d() {}
 /* @__NO_SIDE_EFFECTS__ */ export function* b() {}
 /* @__NO_SIDE_EFFECTS__ */ export async function c() {}
 /* @__NO_SIDE_EFFECTS__ */ export async function* d() {}
+export default /* @__NO_SIDE_EFFECTS__ */ async function() {}
+export default /* @__NO_SIDE_EFFECTS__ */ function() {}
         ",
         // Only "c0" and "c2" should have "no side effects" (Rollup only respects "const" and only for the first one)
         r"
diff --git a/crates/oxc_codegen/tests/integration/snapshots/pure_comments.snap b/crates/oxc_codegen/tests/integration/snapshots/pure_comments.snap
index 210b0dbf4bad3..8c9b21057fb73 100644
--- a/crates/oxc_codegen/tests/integration/snapshots/pure_comments.snap
+++ b/crates/oxc_codegen/tests/integration/snapshots/pure_comments.snap
@@ -128,6 +128,8 @@ export async function* d() {}
 /* @__NO_SIDE_EFFECTS__ */ export function* b() {}
 /* @__NO_SIDE_EFFECTS__ */ export async function c() {}
 /* @__NO_SIDE_EFFECTS__ */ export async function* d() {}
+export default /* @__NO_SIDE_EFFECTS__ */ async function() {}
+export default /* @__NO_SIDE_EFFECTS__ */ function() {}
         
 ----------
 /* @__NO_SIDE_EFFECTS__ */
@@ -138,6 +140,10 @@ export function* b() {}
 export async function c() {}
 /* @__NO_SIDE_EFFECTS__ */
 export async function* d() {}
+/* @__NO_SIDE_EFFECTS__ */
+export default async function() {}
+/* @__NO_SIDE_EFFECTS__ */
+export default function() {}
 
 ########## 7
 
diff --git a/crates/oxc_parser/src/js/module.rs b/crates/oxc_parser/src/js/module.rs
index 40936005154d1..b9ee36cf4b0f1 100644
--- a/crates/oxc_parser/src/js/module.rs
+++ b/crates/oxc_parser/src/js/module.rs
@@ -383,6 +383,8 @@ impl<'a> ParserImpl<'a> {
     ) -> Result<Box<'a, ExportDefaultDeclaration<'a>>> {
         let exported = self.parse_keyword_identifier(Kind::Default);
         let decl_span = self.start_span();
+        let has_no_side_effects_comment =
+            self.lexer.trivia_builder.previous_token_has_no_side_effects_comment();
         // For tc39/proposal-decorators
         // For more information, please refer to <https://babeljs.io/docs/babel-plugin-proposal-decorators#decoratorsbeforeexport>
         self.eat_decorators()?;
@@ -406,9 +408,13 @@ impl<'a> ParserImpl<'a> {
                     }
                 })?
             }
-            _ if self.at_function_with_async() => self
-                .parse_function_impl(FunctionKind::DefaultExport)
-                .map(ExportDefaultDeclarationKind::FunctionDeclaration)?,
+            _ if self.at_function_with_async() => {
+                let mut func = self.parse_function_impl(FunctionKind::DefaultExport)?;
+                if has_no_side_effects_comment {
+                    func.pure = true;
+                }
+                ExportDefaultDeclarationKind::FunctionDeclaration(func)
+            }
             _ => {
                 let decl = self
                     .parse_assignment_expression_or_higher()