Bundle fmt 9.1.0's std.h, and provide a header to include either it or the external fmt's version (#2539)

include/spdlog/fmt/bundled/std.h

@@ -0,0 +1,171 @@
+// Formatting library for C++ - formatters for standard library types
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_STD_H_
+#define FMT_STD_H_
+
+#include <thread>
+#include <type_traits>
+#include <utility>
+
+#include "ostream.h"
+
+#if FMT_HAS_INCLUDE(<version>)
+#  include <version>
+#endif
+// Checking FMT_CPLUSPLUS for warning suppression in MSVC.
+#if FMT_CPLUSPLUS >= 201703L
+#  if FMT_HAS_INCLUDE(<filesystem>)
+#    include <filesystem>
+#  endif
+#  if FMT_HAS_INCLUDE(<variant>)
+#    include <variant>
+#  endif
+#endif
+
+#ifdef __cpp_lib_filesystem
+FMT_BEGIN_NAMESPACE
+
+namespace detail {
+
+template <typename Char>
+void write_escaped_path(basic_memory_buffer<Char>& quoted,
+                        const std::filesystem::path& p) {
+  write_escaped_string<Char>(std::back_inserter(quoted), p.string<Char>());
+}
+#  ifdef _WIN32
+template <>
+inline void write_escaped_path<char>(basic_memory_buffer<char>& quoted,
+                                     const std::filesystem::path& p) {
+  auto s = p.u8string();
+  write_escaped_string<char>(
+      std::back_inserter(quoted),
+      string_view(reinterpret_cast<const char*>(s.c_str()), s.size()));
+}
+#  endif
+template <>
+inline void write_escaped_path<std::filesystem::path::value_type>(
+    basic_memory_buffer<std::filesystem::path::value_type>& quoted,
+    const std::filesystem::path& p) {
+  write_escaped_string<std::filesystem::path::value_type>(
+      std::back_inserter(quoted), p.native());
+}
+
+}  // namespace detail
+
+template <typename Char>
+struct formatter<std::filesystem::path, Char>
+    : formatter<basic_string_view<Char>> {
+  template <typename FormatContext>
+  auto format(const std::filesystem::path& p, FormatContext& ctx) const ->
+      typename FormatContext::iterator {
+    basic_memory_buffer<Char> quoted;
+    detail::write_escaped_path(quoted, p);
+    return formatter<basic_string_view<Char>>::format(
+        basic_string_view<Char>(quoted.data(), quoted.size()), ctx);
+  }
+};
+FMT_END_NAMESPACE
+#endif
+
+FMT_BEGIN_NAMESPACE
+template <typename Char>
+struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
+FMT_END_NAMESPACE
+
+#ifdef __cpp_lib_variant
+FMT_BEGIN_NAMESPACE
+template <typename Char> struct formatter<std::monostate, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const std::monostate&, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    out = detail::write<Char>(out, "monostate");
+    return out;
+  }
+};
+
+namespace detail {
+
+template <typename T>
+using variant_index_sequence =
+    std::make_index_sequence<std::variant_size<T>::value>;
+
+// variant_size and variant_alternative check.
+template <typename T, typename U = void>
+struct is_variant_like_ : std::false_type {};
+template <typename T>
+struct is_variant_like_<T, std::void_t<decltype(std::variant_size<T>::value)>>
+    : std::true_type {};
+
+// formattable element check
+template <typename T, typename C> class is_variant_formattable_ {
+  template <std::size_t... I>
+  static std::conjunction<
+      is_formattable<std::variant_alternative_t<I, T>, C>...>
+      check(std::index_sequence<I...>);
+
+ public:
+  static constexpr const bool value =
+      decltype(check(variant_index_sequence<T>{}))::value;
+};
+
+template <typename Char, typename OutputIt, typename T>
+auto write_variant_alternative(OutputIt out, const T& v) -> OutputIt {
+  if constexpr (is_string<T>::value)
+    return write_escaped_string<Char>(out, detail::to_string_view(v));
+  else if constexpr (std::is_same_v<T, Char>)
+    return write_escaped_char(out, v);
+  else
+    return write<Char>(out, v);
+}
+
+}  // namespace detail
+
+template <typename T> struct is_variant_like {
+  static constexpr const bool value = detail::is_variant_like_<T>::value;
+};
+
+template <typename T, typename C> struct is_variant_formattable {
+  static constexpr const bool value =
+      detail::is_variant_formattable_<T, C>::value;
+};
+
+template <typename Variant, typename Char>
+struct formatter<
+    Variant, Char,
+    std::enable_if_t<std::conjunction_v<
+        is_variant_like<Variant>, is_variant_formattable<Variant, Char>>>> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const Variant& value, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+
+    out = detail::write<Char>(out, "variant(");
+    std::visit(
+        [&](const auto& v) {
+          out = detail::write_variant_alternative<Char>(out, v);
+        },
+        value);
+    *out++ = ')';
+    return out;
+  }
+};
+FMT_END_NAMESPACE
+#endif
+
+#endif  // FMT_STD_H_

include/spdlog/fmt/std.h

@@ -0,0 +1,23 @@
+//
+// Copyright(c) 2016 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+#pragma once
+//
+// include bundled or external copy of fmtlib's std support (for formatting e.g. std::filesystem::path, std::thread::id, std::monostate,
+// std::variant, ...)
+//
+
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
+#        endif
+#        include <spdlog/fmt/bundled/std.h>
+#    else
+#        include <fmt/std.h>
+#    endif
+#endif