reflection.hpp

Go to the documentation of this file.

// SPDX-FileCopyrightText: 2026 Jarosław Pelczar <jarek@jpelczar.com>
//
// SPDX-License-Identifier: BSD-2-Clause
 
#pragma once
 
#include "../microfmt.hpp"
#include "reflect_annotate.hpp"
 
#if RELOCO_HAS_REFLECTION
 
#include <meta>
#include <string_view>
#include <type_traits>
 
namespace microfmt::detail {
 
template <typename E> inline constexpr bool is_reflect_formattable_enum_v = std::is_enum_v<E>;
 
template <typename T>
inline constexpr bool is_reflect_formattable_struct_v = std::is_class_v<T> && enable_reflect_format<T>::value;
 
} // namespace microfmt::detail
 
namespace microfmt {
 
// ============================================================================
// Formatter for reflected enums (automatic, no opt-in required)
// ============================================================================
template <typename E> struct formatter<E, std::enable_if_t<detail::is_reflect_formattable_enum_v<E>>> {
  constexpr void parse(format_parse_context &ctx) noexcept { (void)ctx; }
 
  void format(E val, const sink &out) const noexcept {
    template for (constexpr auto e : define_static_array(std::meta::enumerators_of(^^E))) {
      constexpr auto enumerator_value = [:e:];
      if (val == enumerator_value) {
        constexpr std::string_view name = std::meta::identifier_of(e);
        out.write(microfmt::string_view(name.data(), name.size()));
        return;
      }
    }
 
    // Fallback: format raw underlying integer if value is unmapped/invalid.
    format_to(out, "{}", static_cast<std::underlying_type_t<E>>(val));
  }
};
 
// ============================================================================
// Formatter for reflected structs & classes (opt-in via enable_reflect_format)
// ============================================================================
template <typename T> struct formatter<T, std::enable_if_t<detail::is_reflect_formattable_struct_v<T>>> {
  constexpr void parse(format_parse_context &ctx) noexcept { (void)ctx; }
 
  void format(const T &val, const sink &out) const noexcept {
    out.put('{');
    bool first = true;
 
    template for (constexpr auto member : define_static_array(
                      std::meta::nonstatic_data_members_of(^^T, std::meta::access_context::current()))) {
      if (!first) {
        out.write(", ");
      }
      first = false;
 
      constexpr std::string_view name = std::meta::identifier_of(member);
      out.write(microfmt::string_view(name.data(), name.size()));
      out.write(": ");
 
      // Format member value recursively via microfmt.
      format_to(out, "{}", val.[:member:]);
    }
 
    out.put('}');
  }
};
 
} // namespace microfmt
 
#endif // RELOCO_HAS_REFLECTION