From 10064d0e1a89a4f48dc1e896de35a65f2ab946f4 Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Sun, 8 Sep 2024 14:04:25 +0200
Subject: [PATCH] LibJS: Reset in_formal_parameter_context after entering a new
 function

Fixes a bug when "'Await' expression is not allowed in formal parameters
of an async function" is thrown for "await" encountered in a function
definition assigned to a default function parameter.

Fixes loading of https://excalidraw.com/
---
 Userland/Libraries/LibJS/Parser.cpp           |  3 +++
 ...in-a-func-def-assigned-to-default-param.js | 23 +++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 Userland/Libraries/LibJS/Tests/regress/allow-await-in-a-func-def-assigned-to-default-param.js

diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index fb82be40893..d72e2f634ff 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -982,6 +982,8 @@ static bool is_simple_parameter_list(Vector<FunctionParameter> const& parameters
 
 RefPtr<FunctionExpression const> Parser::try_parse_arrow_function_expression(bool expect_parens, bool is_async)
 {
+    TemporaryChange in_formal_parameter_context_rollback(m_state.in_formal_parameter_context, false);
+
     if (is_async)
         VERIFY(match(TokenType::Async));
 
@@ -2888,6 +2890,7 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u16 parse_options, O
     TemporaryChange continue_context_rollback(m_state.in_continue_context, false);
     TemporaryChange class_field_initializer_rollback(m_state.in_class_field_initializer, false);
     TemporaryChange might_need_arguments_object_rollback(m_state.function_might_need_arguments_object, false);
+    TemporaryChange in_formal_parameter_context_rollback(m_state.in_formal_parameter_context, false);
 
     constexpr auto is_function_expression = IsSame<FunctionNodeType, FunctionExpression>;
     FunctionKind function_kind;
diff --git a/Userland/Libraries/LibJS/Tests/regress/allow-await-in-a-func-def-assigned-to-default-param.js b/Userland/Libraries/LibJS/Tests/regress/allow-await-in-a-func-def-assigned-to-default-param.js
new file mode 100644
index 00000000000..288c98ca8ce
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/regress/allow-await-in-a-func-def-assigned-to-default-param.js
@@ -0,0 +1,23 @@
+test('Do not throw syntax error when "await" is used in an arrow function definition assigned to a default function parameter', async () => {
+    async function f(
+        g = async () => {
+            await 1;
+        }
+    ) {
+        return await g();
+    }
+
+    expect(await f()).toBe(1);
+});
+
+test('Do not throw syntax error when "await" is used in a function definition assigned to a default function parameter', async () => {
+    async function f(
+        g = async function () {
+            await 1;
+        }
+    ) {
+        return await g();
+    }
+
+    expect(await f()).toBe(1);
+});