From e205a701c134c8c5f24bc3f1bb0559327552c8fc Mon Sep 17 00:00:00 2001
From: Vladislav Shchapov <vladislav@shchapov.ru>
Date: Wed, 3 Jul 2024 21:39:58 +0500
Subject: [PATCH] Fix format of negative std::complex without sign option in
 format string

Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
---
 include/fmt/std.h | 11 ++++++++---
 test/std-test.cc  |  6 ++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/fmt/std.h b/include/fmt/std.h
index 2e6cf12f3f436..244c6e8a1cc00 100644
--- a/include/fmt/std.h
+++ b/include/fmt/std.h
@@ -631,8 +631,7 @@ struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
 #endif  // __cpp_lib_atomic_flag_test
 
 FMT_EXPORT
-template <typename T, typename Char>
-struct formatter<std::complex<T>, Char> {
+template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
  private:
   int width_;
   detail::fill_t fill_;
@@ -666,7 +665,13 @@ struct formatter<std::complex<T>, Char> {
       if (c.real() != 0) {
         auto format_full = detail::string_literal<Char, '(', '{', '}', '+', '{',
                                                   '}', 'i', ')'>{};
-        return fmt::format_to(out, basic_string_view<Char>(format_full),
+        auto format_full_neg =
+            detail::string_literal<Char, '(', '{', '}', '{', '}', 'i', ')'>{};
+
+        if (c.imag() >= 0)
+          return fmt::format_to(out, basic_string_view<Char>(format_full),
+                                f->nested(c.real()), f->nested(c.imag()));
+        return fmt::format_to(out, basic_string_view<Char>(format_full_neg),
                               f->nested(c.real()), f->nested(c.imag()));
       }
       auto format_imag = detail::string_literal<Char, '{', '}', 'i'>{};
diff --git a/test/std-test.cc b/test/std-test.cc
index 17c95cfe57ed2..618bf477fe9de 100644
--- a/test/std-test.cc
+++ b/test/std-test.cc
@@ -67,9 +67,15 @@ TEST(std_test, thread_id) {
 
 TEST(std_test, complex) {
   EXPECT_EQ(fmt::format("{}", std::complex<double>(1, 2.2)), "(1+2.2i)");
+  EXPECT_EQ(fmt::format("{}", std::complex<double>(1, -2.2)), "(1-2.2i)");
   EXPECT_EQ(fmt::format("{}", std::complex<double>(0, 2.2)), "2.2i");
+  EXPECT_EQ(fmt::format("{}", std::complex<double>(0, -2.2)), "-2.2i");
   EXPECT_EQ(fmt::format("{:>20.2f}", std::complex<double>(1, 2.2)),
             "        (1.00+2.20i)");
+  EXPECT_EQ(fmt::format("{:<20.2f}", std::complex<double>(1, 2.2)),
+            "(1.00+2.20i)        ");
+  EXPECT_EQ(fmt::format("{:<20.2f}", std::complex<double>(1, -2.2)),
+            "(1.00-2.20i)        ");
 }
 
 #ifdef __cpp_lib_source_location