From 2e526a664a8b2df428e2f1df790d2f3a40c8e80d Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Wed, 6 Mar 2019 07:59:23 -0800
Subject: [PATCH] Fix handling of output iterator in ranges

---
 include/fmt/ranges.h | 51 ++++++++++++++++++++------------------------
 test/ranges-test.cc  | 15 +++++++++----
 2 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 5145fc06..fd8d0203 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -55,21 +55,22 @@ struct formatting_tuple : formatting_base<Char> {
 namespace internal {
 
 template <typename RangeT, typename OutputIterator>
-void copy(const RangeT& range, OutputIterator out) {
+OutputIterator copy(const RangeT& range, OutputIterator out) {
   for (auto it = range.begin(), end = range.end(); it != end; ++it)
     *out++ = *it;
+  return out;
 }
 
 template <typename OutputIterator>
-void copy(const char* str, OutputIterator out) {
-  const char* p_curr = str;
-  while (*p_curr) {
-    *out++ = *p_curr++;
-  }
+OutputIterator copy(const char* str, OutputIterator out) {
+  while (*str) *out++ = *str++;
+  return out;
 }
 
-template <typename OutputIterator> void copy(char ch, OutputIterator out) {
+template <typename OutputIterator>
+OutputIterator copy(char ch, OutputIterator out) {
   *out++ = ch;
+  return out;
 }
 
 /// Return true value if T has std::string interface, like std::string_view.
@@ -211,12 +212,12 @@ struct formatter<
         if (formatting.add_prepostfix_space) {
           *out++ = ' ';
         }
-        internal::copy(formatting.delimiter, out);
+        out = internal::copy(formatting.delimiter, out);
       }
-      format_to(out,
-                internal::format_str_quoted(
-                    (formatting.add_delimiter_spaces && i > 0), v),
-                v);
+      out = format_to(out,
+                      internal::format_str_quoted(
+                          (formatting.add_delimiter_spaces && i > 0), v),
+                      v);
       ++i;
     }
 
@@ -268,30 +269,24 @@ struct formatter<RangeT, Char,
   template <typename FormatContext>
   typename FormatContext::iterator format(const RangeT& values,
                                           FormatContext& ctx) {
-    auto out = ctx.out();
-    internal::copy(formatting.prefix, out);
+    auto out = internal::copy(formatting.prefix, ctx.out());
     std::size_t i = 0;
     for (auto it = values.begin(), end = values.end(); it != end; ++it) {
       if (i > 0) {
-        if (formatting.add_prepostfix_space) {
-          *out++ = ' ';
-        }
-        internal::copy(formatting.delimiter, out);
+        if (formatting.add_prepostfix_space) *out++ = ' ';
+        out = internal::copy(formatting.delimiter, out);
       }
-      format_to(out,
-                internal::format_str_quoted(
-                    (formatting.add_delimiter_spaces && i > 0), *it),
-                *it);
+      out = format_to(out,
+                      internal::format_str_quoted(
+                          (formatting.add_delimiter_spaces && i > 0), *it),
+                      *it);
       if (++i > formatting.range_length_limit) {
-        format_to(out, " ... <other elements>");
+        out = format_to(out, " ... <other elements>");
         break;
       }
     }
-    if (formatting.add_prepostfix_space) {
-      *out++ = ' ';
-    }
-    internal::copy(formatting.postfix, out);
-    return ctx.out();
+    if (formatting.add_prepostfix_space) *out++ = ' ';
+    return internal::copy(formatting.postfix, out);
   }
 };
 
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index 97359973..b8990717 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -39,14 +39,14 @@ TEST(RangesTest, FormatMap) {
 }
 
 TEST(RangesTest, FormatPair) {
-  std::pair<int64_t, float> pa1{42, 3.14159265358979f};
-  EXPECT_EQ("(42, 3.14159)", fmt::format("{}", pa1));
+  std::pair<int64_t, float> pa1{42, 1.5f};
+  EXPECT_EQ("(42, 1.5)", fmt::format("{}", pa1));
 }
 
 TEST(RangesTest, FormatTuple) {
-  std::tuple<int64_t, float, std::string, char> tu1{42, 3.14159265358979f,
+  std::tuple<int64_t, float, std::string, char> tu1{42, 1.5f,
                                                     "this is tuple", 'i'};
-  EXPECT_EQ("(42, 3.14159, \"this is tuple\", 'i')", fmt::format("{}", tu1));
+  EXPECT_EQ("(42, 1.5, \"this is tuple\", 'i')", fmt::format("{}", tu1));
 }
 
 struct my_struct {
@@ -80,5 +80,12 @@ TEST(RangesTest, FormatStruct) {
   EXPECT_EQ("(13, \"my struct\")", fmt::format("{}", mst));
 }
 
+TEST(RangesTest, FormatTo) {
+  char buf[10];
+  auto end = fmt::format_to(buf, "{}", std::vector{1, 2, 3});
+  *end = '\0';
+  EXPECT_STREQ(buf, "{1, 2, 3}");
+}
+
 #endif  // (__cplusplus > 201402L) || (defined(_MSVC_LANG) && _MSVC_LANG >
         // 201402L && _MSC_VER >= 1910)