From 3c9bbc96653fe8480e30bd6ab947a31a650721d5 Mon Sep 17 00:00:00 2001
From: Brian Smith <brian@dbsoft.org>
Date: Fri, 6 Mar 2026 13:13:21 -0600
Subject: [PATCH] Issue #2304 - Part 1 - Prerequisite: Make Handle<Maybe<>>
 more convenient. This is required to implement JS::NothingHandleValue.
 https://bugzilla.mozilla.org/show_bug.cgi?id=1631114

---
 js/public/RootingAPI.h | 28 ++++++++++++++++++++++++++++
 js/public/Value.h      |  1 +
 js/src/vm/Value.cpp    |  2 ++
 3 files changed, 31 insertions(+)

diff --git a/js/public/RootingAPI.h b/js/public/RootingAPI.h
index e03bc56fb7..137a86e48f 100644
--- a/js/public/RootingAPI.h
+++ b/js/public/RootingAPI.h
@@ -10,6 +10,7 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/GuardObjects.h"
 #include "mozilla/LinkedList.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/Move.h"
 #include "mozilla/TypeTraits.h"
 
@@ -1278,6 +1279,33 @@ class MutableWrappedPtrOperations<UniquePtr<T, D>, Container>
     void reset(T* ptr = T()) { uniquePtr().reset(ptr); }
 };
 
+template <typename T, typename Container>
+class WrappedPtrOperations<mozilla::Maybe<T>, Container> {
+  const mozilla::Maybe<T>& maybe() const {
+    return static_cast<const Container*>(this)->get();
+  }
+
+ public:
+  // This only supports a subset of Maybe's interface.
+  bool isSome() const { return maybe().isSome(); }
+  bool isNothing() const { return maybe().isNothing(); }
+  const T value() const { return maybe().value(); }
+  const T* operator->() const { return maybe().ptr(); }
+  const T& operator*() const { return maybe().ref(); }
+};
+
+template <typename T, typename Container>
+class MutableWrappedPtrOperations<mozilla::Maybe<T>, Container>
+    : public WrappedPtrOperations<mozilla::Maybe<T>, Container> {
+  mozilla::Maybe<T>& maybe() { return static_cast<Container*>(this)->get(); }
+
+ public:
+  // This only supports a subset of Maybe's interface.
+  T* operator->() { return maybe().ptr(); }
+  T& operator*() { return maybe().ref(); }
+  void reset() { return maybe().reset(); }
+};
+
 namespace gc {
 
 template <typename T, typename TraceCallbacks>
diff --git a/js/public/Value.h b/js/public/Value.h
index a6ceaad669..46c3995f24 100644
--- a/js/public/Value.h
+++ b/js/public/Value.h
@@ -1535,6 +1535,7 @@ extern JS_PUBLIC_DATA(const HandleValue) NullHandleValue;
 extern JS_PUBLIC_DATA(const HandleValue) UndefinedHandleValue;
 extern JS_PUBLIC_DATA(const HandleValue) TrueHandleValue;
 extern JS_PUBLIC_DATA(const HandleValue) FalseHandleValue;
+extern JS_PUBLIC_DATA(const Handle<mozilla::Maybe<Value>>) NothingHandleValue;
 
 } // namespace JS
 
diff --git a/js/src/vm/Value.cpp b/js/src/vm/Value.cpp
index 674b5ec774..6df86aa0f2 100644
--- a/js/src/vm/Value.cpp
+++ b/js/src/vm/Value.cpp
@@ -9,6 +9,7 @@ static const JS::Value JSVAL_NULL  = JS::Value::fromTagAndPayload(JSVAL_TAG_NULL
 static const JS::Value JSVAL_FALSE = JS::Value::fromTagAndPayload(JSVAL_TAG_BOOLEAN,   false);
 static const JS::Value JSVAL_TRUE  = JS::Value::fromTagAndPayload(JSVAL_TAG_BOOLEAN,   true);
 static const JS::Value JSVAL_VOID  = JS::Value::fromTagAndPayload(JSVAL_TAG_UNDEFINED, 0);
+static const mozilla::Maybe<JS::Value> JSVAL_NOTHING;
 
 namespace JS {
 
@@ -16,5 +17,6 @@ const HandleValue NullHandleValue = HandleValue::fromMarkedLocation(&JSVAL_NULL)
 const HandleValue UndefinedHandleValue = HandleValue::fromMarkedLocation(&JSVAL_VOID);
 const HandleValue TrueHandleValue = HandleValue::fromMarkedLocation(&JSVAL_TRUE);
 const HandleValue FalseHandleValue = HandleValue::fromMarkedLocation(&JSVAL_FALSE);
+const Handle<mozilla::Maybe<Value>> NothingHandleValue = Handle<mozilla::Maybe<Value>>::fromMarkedLocation(&JSVAL_NOTHING);
 
 } // namespace JS