feat: Allow fmt::join to accept rvalue tuples

include/fmt/chrono.h

@@ -1598,7 +1598,7 @@ class get_locale {
     ignore_unused(loc);
     ::new (&locale_) std::locale(
 #if FMT_USE_LOCALE
-      loc.template get<std::locale>()
+        loc.template get<std::locale>()
 #endif
     );
   }

include/fmt/ranges.h

@@ -147,7 +147,8 @@ using make_index_sequence = make_integer_sequence<size_t, N>;
 #endif
 
 template <typename T>
-using tuple_index_sequence = make_index_sequence<std::tuple_size<T>::value>;
+using tuple_index_sequence =
+    make_index_sequence<std::tuple_size<remove_cvref_t<T>>::value>;
 
 template <typename T, typename C, bool = is_tuple_like_<T>::value>
 class is_tuple_formattable_ {
@@ -282,12 +283,14 @@ template <typename FormatContext> struct format_tuple_element {
 FMT_EXPORT
 template <typename T> struct is_tuple_like {
   static constexpr bool value =
-      detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
+      detail::is_tuple_like_<remove_cvref_t<T>>::value &&
+      !detail::is_range_<T>::value;
 };
 
 FMT_EXPORT
 template <typename T, typename C> struct is_tuple_formattable {
-  static constexpr bool value = detail::is_tuple_formattable_<T, C>::value;
+  static constexpr bool value =
+      detail::is_tuple_formattable_<remove_cvref_t<T>, C>::value;
 };
 
 template <typename Tuple, typename Char>
@@ -673,11 +676,11 @@ struct formatter<join_view<It, Sentinel, Char>, Char> {
 
 FMT_EXPORT
 template <typename Tuple, typename Char> struct tuple_join_view : detail::view {
-  const Tuple& tuple;
+  Tuple tuple;
   basic_string_view<Char> sep;
 
-  tuple_join_view(const Tuple& t, basic_string_view<Char> s)
-      : tuple(t), sep{s} {}
+  tuple_join_view(Tuple&& t, basic_string_view<Char> s)
+      : tuple(std::forward<Tuple>(t)), sep{s} {}
 };
 
 // Define FMT_TUPLE_JOIN_SPECIFIERS to enable experimental format specifiers
@@ -691,13 +694,13 @@ template <typename Tuple, typename Char>
 struct formatter<tuple_join_view<Tuple, Char>, Char,
                  enable_if_t<is_tuple_like<Tuple>::value>> {
   FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
-    return do_parse(ctx, std::tuple_size<Tuple>());
+    return do_parse(ctx, std::tuple_size<remove_cvref_t<Tuple>>());
   }
 
   template <typename FormatContext>
   auto format(const tuple_join_view<Tuple, Char>& value,
               FormatContext& ctx) const -> typename FormatContext::iterator {
-    return do_format(value, ctx, std::tuple_size<Tuple>());
+    return do_format(value, ctx, std::tuple_size<remove_cvref_t<Tuple>>());
   }
 
  private:
@@ -716,7 +719,9 @@ struct formatter<tuple_join_view<Tuple, Char>, Char,
       -> const Char* {
     auto end = ctx.begin();
 #if FMT_TUPLE_JOIN_SPECIFIERS
-    end = std::get<std::tuple_size<Tuple>::value - N>(formatters_).parse(ctx);
+    end =
+        std::get<std::tuple_size<remove_cvref_t<Tuple>>::value - N>(formatters_)
+            .parse(ctx);
     if (N > 1) {
       auto end1 = do_parse(ctx, std::integral_constant<size_t, N - 1>());
       if (end != end1)
@@ -739,8 +744,10 @@ struct formatter<tuple_join_view<Tuple, Char>, Char,
       typename FormatContext::iterator {
     using std::get;
     auto out =
-        std::get<std::tuple_size<Tuple>::value - N>(formatters_)
-            .format(get<std::tuple_size<Tuple>::value - N>(value.tuple), ctx);
+        std::get<std::tuple_size<remove_cvref_t<Tuple>>::value - N>(formatters_)
+            .format(get<std::tuple_size<remove_cvref_t<Tuple>>::value - N>(
+                        value.tuple),
+                    ctx);
     if (N <= 1) return out;
     out = detail::copy<Char>(value.sep, out);
     ctx.advance_to(out);
@@ -826,9 +833,9 @@ auto join(Range&& r, string_view sep)
  *     // Output: 1, a
  */
 template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
-FMT_CONSTEXPR auto join(const Tuple& tuple, string_view sep)
+FMT_CONSTEXPR auto join(Tuple&& tuple, string_view sep)
     -> tuple_join_view<Tuple, char> {
-  return {tuple, sep};
+  return {std::forward<Tuple>(tuple), sep};
 }
 
 /**

include/fmt/xchar.h

@@ -156,9 +156,9 @@ auto join(std::initializer_list<T> list, wstring_view sep)
 }
 
 template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
-auto join(const Tuple& tuple, basic_string_view<wchar_t> sep)
+auto join(Tuple&& tuple, basic_string_view<wchar_t> sep)
     -> tuple_join_view<Tuple, wchar_t> {
-  return {tuple, sep};
+  return {std::forward<Tuple>(tuple), sep};
 }
 
 template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>

test/ranges-test.cc

@@ -194,6 +194,11 @@ TEST(ranges_test, format_tuple) {
   EXPECT_TRUE((fmt::is_formattable<std::tuple<int, float>>::value));
 }
 
+TEST(ranges_test, format_tuple_rvalue) {
+  EXPECT_EQ(fmt::format("{}", std::make_tuple(42, 1.5f, "this is tuple", 'i')),
+            "(42, 1.5, \"this is tuple\", 'i')");
+}
+
 struct not_default_formattable {};
 struct bad_format {};