From 1b94271ff69f1159abb0907dd5a18700531b2922 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Sat, 3 Sep 2022 10:35:57 -0700
Subject: [PATCH] Add support for UTF-8 digit separators

---
 include/fmt/format-inl.h | 12 +++++-------
 include/fmt/format.h     | 13 ++++++-------
 test/format-test.cc      | 14 ++++++++++++--
 3 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 9ce96b1d..d77e5c82 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -123,8 +123,7 @@ FMT_FUNC auto write_int(appender out, basic_format_arg<format_context> value,
   // We cannot use the num_put<char> facet because it may produce output in
   // a wrong encoding.
   if (!std::has_facet<format_facet<std::locale>>(locale)) return {};
-  std::use_facet<format_facet<std::locale>>(locale).put(out, value, specs,
-                                                        locale);
+  std::use_facet<format_facet<std::locale>>(locale).put(out, value, specs);
   return true;
 #endif
   return false;
@@ -133,13 +132,13 @@ FMT_FUNC auto write_int(appender out, basic_format_arg<format_context> value,
 struct localize_int {
   appender out;
   const format_specs& specs;
-  locale_ref loc;
+  std::string sep;
 
   template <typename T, FMT_ENABLE_IF(detail::is_integer<T>::value)>
   void operator()(T value) {
     auto arg = make_write_int_arg(value, specs.sign);
     write_int(out, static_cast<uint64_or_128_t<T>>(arg.abs_value), arg.prefix,
-              specs, digit_grouping<char>(loc));
+              specs, digit_grouping<char>("\3", sep));
   }
   template <typename T, FMT_ENABLE_IF(!detail::is_integer<T>::value)>
   void operator()(T) {}
@@ -152,9 +151,8 @@ template <typename Locale> typename Locale::id format_facet<Locale>::id;
 template <>
 FMT_API FMT_FUNC void format_facet<std::locale>::do_put(
     appender out, basic_format_arg<format_context> val,
-    const format_specs& specs, std::locale& loc) const {
-  visit_format_arg(detail::localize_int{out, specs, detail::locale_ref(loc)},
-                   val);
+    const format_specs& specs) const {
+  visit_format_arg(detail::localize_int{out, specs, separator_}, val);
 }
 #endif
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index f03a59f9..ab98dbd5 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -993,7 +993,7 @@ template <typename Locale> class format_facet : public Locale::facet {
 
  protected:
   virtual void do_put(appender out, basic_format_arg<format_context> val,
-                      const format_specs& specs, Locale& loc) const;
+                      const format_specs& specs) const;
 
  public:
   static FMT_API typename Locale::id id;
@@ -1002,8 +1002,8 @@ template <typename Locale> class format_facet : public Locale::facet {
       : separator_(sep.data(), sep.size()) {}
 
   void put(appender out, basic_format_arg<format_context> val,
-           const format_specs& specs, Locale& loc) const {
-    do_put(out, val, specs, loc);
+           const format_specs& specs) const {
+    do_put(out, val, specs);
   }
 };
 
@@ -1981,9 +1981,8 @@ template <typename Char> class digit_grouping {
     grouping_ = sep.grouping;
     if (sep.thousands_sep) thousands_sep_.assign(1, sep.thousands_sep);
   }
-  explicit digit_grouping(thousands_sep_result<Char> sep)
-      : grouping_(sep.grouping),
-        thousands_sep_(sep.thousands_sep ? 1 : 0, sep.thousands_sep) {}
+  digit_grouping(std::string grouping, std::string sep)
+      : grouping_(std::move(grouping)), thousands_sep_(std::move(sep)) {}
 
   bool has_separator() const { return !thousands_sep_.empty(); }
 
@@ -3950,7 +3949,7 @@ template <typename T> struct formatter<group_digits_view<T>> : formatter<T> {
         specs_.precision, specs_.precision_ref, ctx);
     return detail::write_int(
         ctx.out(), static_cast<detail::uint64_or_128_t<T>>(t.value), 0, specs_,
-        detail::digit_grouping<char>({"\3", ','}));
+        detail::digit_grouping<char>("\3", ","));
   }
 };
 
diff --git a/test/format-test.cc b/test/format-test.cc
index ee82bd9e..6fb38cb9 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -2330,12 +2330,12 @@ class format_facet : public fmt::format_facet<std::locale> {
   };
 
   void do_put(fmt::appender out, fmt::basic_format_arg<fmt::format_context> arg,
-              const fmt::format_specs&, std::locale&) const override;
+              const fmt::format_specs&) const override;
 };
 
 void format_facet::do_put(fmt::appender out,
                           fmt::basic_format_arg<fmt::format_context> arg,
-                          const fmt::format_specs&, std::locale&) const {
+                          const fmt::format_specs&) const {
   visit_format_arg(int_formatter{out}, arg);
 }
 
@@ -2345,4 +2345,14 @@ TEST(format_test, format_facet) {
   EXPECT_EQ(fmt::format(loc, "{:L}", -42), "[-42]");
 }
 
+TEST(format_test, format_facet_separator) {
+  // U+2019 RIGHT SINGLE QUOTATION MARK is a digit separator in the de_CH
+  // locale.
+  auto loc = std::locale(std::locale(),
+                         new fmt::format_facet<std::locale>("\xe2\x80\x99"));
+  EXPECT_EQ(fmt::format(loc, "{:L}", 1000),
+            "1\xe2\x80\x99"
+            "000");
+}
+
 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR