From f90612171b99e7036cb822d13b6ef34aad6c5187 Mon Sep 17 00:00:00 2001
From: Jakub Piasecki <piaseckijakub@meta.com>
Date: Fri, 27 Feb 2026 06:45:35 -0800
Subject: [PATCH] Handle constexpr functions (#55801)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55801

Changelog: [Internal]

Handle `constexpr` functions in the C++ API snapshot

Reviewed By: javache

Differential Revision: D94658128

fbshipit-source-id: 9e380de951e46dff72ba40c8726e46c01340a9a8
---
 scripts/cxx-api/parser/main.py                 |  2 ++
 scripts/cxx-api/parser/member.py               |  5 +++++
 .../snapshot.api                               |  1 +
 .../test.h                                     | 14 ++++++++++++++
 .../snapshot.api                               |  4 ++++
 .../should_handle_constexpr_method/test.h      | 18 ++++++++++++++++++
 6 files changed, 44 insertions(+)
 create mode 100644 scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/snapshot.api
 create mode 100644 scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/test.h
 create mode 100644 scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/snapshot.api
 create mode 100644 scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/test.h

diff --git a/scripts/cxx-api/parser/main.py b/scripts/cxx-api/parser/main.py
index 97c2b31a198..341c1958328 100644
--- a/scripts/cxx-api/parser/main.py
+++ b/scripts/cxx-api/parser/main.py
@@ -316,6 +316,7 @@ def get_function_member(
     function_arg_string = function_def.get_argsstring()
     is_pure_virtual = function_def.get_virt() == "pure-virtual"
     function_virtual = function_def.get_virt() == "virtual" or is_pure_virtual
+    is_constexpr = function_def.constexpr == "yes"
 
     # Doxygen incorrectly merges "=0" into the return type for pure-virtual
     # functions using trailing return types (e.g. "auto f() -> T = 0").
@@ -333,6 +334,7 @@ def get_function_member(
         is_pure_virtual,
         is_static,
         doxygen_params,
+        is_constexpr,
     )
 
     function.add_template(get_template_params(function_def))
diff --git a/scripts/cxx-api/parser/member.py b/scripts/cxx-api/parser/member.py
index c61ac0cf282..6eb98cd5a04 100644
--- a/scripts/cxx-api/parser/member.py
+++ b/scripts/cxx-api/parser/member.py
@@ -206,11 +206,13 @@ class FunctionMember(Member):
         is_pure_virtual: bool,
         is_static: bool,
         doxygen_params: list[Argument] | None = None,
+        is_constexpr: bool = False,
     ) -> None:
         super().__init__(name, visibility)
         self.type: str = type
         self.is_virtual: bool = is_virtual
         self.is_static: bool = is_static
+        self.is_constexpr: bool = is_constexpr
         parsed_arguments, self.modifiers = parse_arg_string(arg_string)
         self.arguments = (
             doxygen_params if doxygen_params is not None else parsed_arguments
@@ -258,6 +260,9 @@ class FunctionMember(Member):
         if self.is_static:
             result += "static "
 
+        if self.is_constexpr:
+            result += "constexpr "
+
         if self.type:
             result += f"{self.type} "
 
diff --git a/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/snapshot.api b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/snapshot.api
new file mode 100644
index 00000000000..c11a40ff8fe
--- /dev/null
+++ b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/snapshot.api
@@ -0,0 +1 @@
+constexpr int test::makeValue();
diff --git a/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/test.h b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/test.h
new file mode 100644
index 00000000000..47c46f7f345
--- /dev/null
+++ b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_free_function/test.h
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+namespace test {
+
+constexpr int makeValue();
+
+} // namespace test
diff --git a/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/snapshot.api b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/snapshot.api
new file mode 100644
index 00000000000..26c2c415c59
--- /dev/null
+++ b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/snapshot.api
@@ -0,0 +1,4 @@
+class test::Clss {
+  public constexpr int getValue() const;
+  public static constexpr int getDefault();
+}
diff --git a/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/test.h b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/test.h
new file mode 100644
index 00000000000..47220d4cc0a
--- /dev/null
+++ b/scripts/cxx-api/tests/snapshots/should_handle_constexpr_method/test.h
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+namespace test {
+
+class Clss {
+ public:
+  constexpr int getValue() const;
+  static constexpr int getDefault();
+};
+
+} // namespace test