From 892c7d980e3e38b6e11a5764f153867b101c9c87 Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Sun, 26 Oct 2025 12:33:54 +0100
Subject: [PATCH] LibJS: Let JS::Script remember whether its code is strict
 mode

We don't want to rely on having the AST node just to answer the question
"is this script strict mode?"
---
 Libraries/LibJS/Bytecode/Interpreter.cpp | 2 +-
 Libraries/LibJS/Script.cpp               | 7 +++++--
 Libraries/LibJS/Script.h                 | 6 +++++-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/Libraries/LibJS/Bytecode/Interpreter.cpp b/Libraries/LibJS/Bytecode/Interpreter.cpp
index f7a61ab0723..9f8f31bb05e 100644
--- a/Libraries/LibJS/Bytecode/Interpreter.cpp
+++ b/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -250,7 +250,7 @@ ThrowCompletionOr<Value> Interpreter::run(Script& script_record, GC::Ptr<Environ
     // 8. Set the PrivateEnvironment of scriptContext to null.
 
     // NOTE: This isn't in the spec, but we require it.
-    script_context->is_strict_mode = script_record.parse_node().is_strict_mode();
+    script_context->is_strict_mode = script_record.is_strict_mode();
 
     // 9. Suspend the currently running execution context.
     // 10. Push scriptContext onto the execution context stack; scriptContext is now the running execution context.
diff --git a/Libraries/LibJS/Script.cpp b/Libraries/LibJS/Script.cpp
index 99a80d43528..ab3851aba85 100644
--- a/Libraries/LibJS/Script.cpp
+++ b/Libraries/LibJS/Script.cpp
@@ -25,15 +25,18 @@ Result<GC::Ref<Script>, Vector<ParserError>> Script::parse(StringView source_tex
     if (parser.has_errors())
         return parser.errors();
 
+    bool strict_mode = script->is_strict_mode();
+
     // 3. Return Script Record { [[Realm]]: realm, [[ECMAScriptCode]]: script, [[HostDefined]]: hostDefined }.
-    return realm.heap().allocate<Script>(realm, filename, move(script), host_defined);
+    return realm.heap().allocate<Script>(realm, filename, move(script), host_defined, strict_mode);
 }
 
-Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined)
+Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined, bool strict_mode)
     : m_realm(realm)
     , m_parse_node(move(parse_node))
     , m_filename(filename)
     , m_host_defined(host_defined)
+    , m_strict_mode(strict_mode)
 {
 }
 
diff --git a/Libraries/LibJS/Script.h b/Libraries/LibJS/Script.h
index f020299da33..ee9e33d9fce 100644
--- a/Libraries/LibJS/Script.h
+++ b/Libraries/LibJS/Script.h
@@ -46,8 +46,10 @@ public:
     HostDefined* host_defined() const { return m_host_defined; }
     StringView filename() const LIFETIME_BOUND { return m_filename; }
 
+    [[nodiscard]] bool is_strict_mode() const { return m_strict_mode; }
+
 private:
-    Script(Realm&, StringView filename, NonnullRefPtr<Program>, HostDefined* = nullptr);
+    Script(Realm&, StringView filename, NonnullRefPtr<Program>, HostDefined*, bool strict_mode);
 
     virtual void visit_edges(Cell::Visitor&) override;
 
@@ -58,6 +60,8 @@ private:
     // Needed for potential lookups of modules.
     ByteString m_filename;
     HostDefined* m_host_defined { nullptr }; // [[HostDefined]]
+
+    bool m_strict_mode { false };
 };
 
 }