From 1919e780940e03ed3c60acf1b6bf871df8336e13 Mon Sep 17 00:00:00 2001
From: Alexander Karatarakis <alex@karatarakis.com>
Date: Wed, 4 Dec 2024 15:01:50 -0800
Subject: [PATCH] [reflection] Add customization point for users to supply
 reflection info

This is useful e.g. in really big structs that can have reflection
info provided by codegen
---
 include/fixed_containers/reflection.hpp | 15 ++++++++++-----
 include/fixed_containers/tuples.hpp     | 11 ++++++++++-
 test/reflection_test.cpp                | 25 +++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/include/fixed_containers/reflection.hpp b/include/fixed_containers/reflection.hpp
index 98266042..c4cc030e 100644
--- a/include/fixed_containers/reflection.hpp
+++ b/include/fixed_containers/reflection.hpp
@@ -211,11 +211,16 @@ constexpr auto field_names_of_impl(const T& instance)
     return output;
 }
 
-template <typename T>
-inline constexpr auto FIELD_NAMES =
-    field_names_of_impl<field_count_of_impl(std::decay_t<T>{})>(std::decay_t<T>{});
 }  // namespace fixed_containers::reflection_detail
 
+namespace fixed_containers::reflection::customize
+{
+template <typename T>
+inline constexpr auto FIELD_NAMES = fixed_containers::reflection_detail::field_names_of_impl<
+    fixed_containers::reflection_detail::field_count_of_impl(std::decay_t<T>{})>(std::decay_t<T>{});
+
+}  // namespace fixed_containers::reflection::customize
+
 namespace fixed_containers::reflection
 {
 template <typename T>
@@ -225,14 +230,14 @@ template <typename T>
     requires(Reflectable<std::decay_t<T>>)
 constexpr std::size_t field_count_of()
 {
-    return reflection_detail::FIELD_NAMES<std::decay_t<T>>.size();
+    return fixed_containers::reflection::customize::FIELD_NAMES<std::decay_t<T>>.size();
 }
 
 template <typename T>
     requires(Reflectable<std::decay_t<T>>)
 constexpr const auto& field_names_of()
 {
-    return reflection_detail::FIELD_NAMES<std::decay_t<T>>;
+    return fixed_containers::reflection::customize::FIELD_NAMES<std::decay_t<T>>;
 }
 
 template <typename T, typename Func>
diff --git a/include/fixed_containers/tuples.hpp b/include/fixed_containers/tuples.hpp
index 0a5fade1..dead783e 100644
--- a/include/fixed_containers/tuples.hpp
+++ b/include/fixed_containers/tuples.hpp
@@ -7,13 +7,22 @@
 #include <tuple>
 #include <utility>
 
-namespace fixed_containers::tuples
+namespace fixed_containers::tuples::customize
 {
 template <std::size_t FIELD_COUNT, typename T>
 constexpr auto as_tuple_view(T& data)
 {
     return as_tuple_view_detail::as_tuple_view<FIELD_COUNT, T>(data);
 }
+}  // namespace fixed_containers::tuples::customize
+
+namespace fixed_containers::tuples
+{
+template <std::size_t FIELD_COUNT, typename T>
+constexpr auto as_tuple_view(T& data)
+{
+    return fixed_containers::tuples::customize::as_tuple_view<FIELD_COUNT, T>(data);
+}
 
 template <typename Tuple, typename Func>
     requires(std::tuple_size_v<std::decay_t<Tuple>> == 0)
diff --git a/test/reflection_test.cpp b/test/reflection_test.cpp
index 2e49f84c..f6e449bc 100644
--- a/test/reflection_test.cpp
+++ b/test/reflection_test.cpp
@@ -605,4 +605,29 @@ TEST(Reflection, MockFailingAddressOfOperator)
 
 }  // namespace fixed_containers
 
+struct MyCustomStruct
+{
+    int a{};
+    int b{};
+    int c{};
+    double d{};  // Customization will ignore this field to show the customization is applied
+};
+
+template <>
+constexpr auto fixed_containers::tuples::customize::as_tuple_view<3, MyCustomStruct>(
+    MyCustomStruct& data)
+{
+    return std::tie(data.a, data.b, data.c);
+}
+
+template <>
+inline constexpr auto fixed_containers::reflection::customize::FIELD_NAMES<MyCustomStruct> =
+    make_fixed_vector<std::string_view>({
+        "a",
+        "b",
+        "c",
+    });
+
+static_assert(fixed_containers::reflection::field_names_of<MyCustomStruct>().size() == 3);
+
 #endif