From 87c066a35b7cc70bb7d438a543c8b49b577e61f4 Mon Sep 17 00:00:00 2001
From: Shawn Zhong <github@shawnzhong.com>
Date: Tue, 24 Jan 2023 14:30:00 -0600
Subject: [PATCH] Implement `println` (#3267)

---
 include/fmt/core.h    | 30 ++++++++++++++++++++++++++++++
 include/fmt/ostream.h | 13 +++++++++++++
 include/fmt/xchar.h   |  9 +++++++++
 test/format-test.cc   |  3 +++
 test/ostream-test.cc  | 14 +++++++++++---
 test/xchar-test.cc    | 19 +++++++++++++++----
 6 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index f7656da0..8942ad3e 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -3009,6 +3009,36 @@ FMT_INLINE void print(std::FILE* f, format_string<T...> fmt, T&&... args) {
                            : detail::vprint_mojibake(f, fmt, vargs);
 }
 
+/**
+  \rst
+  Formats ``args`` according to specifications in ``fmt`` and writes the
+  output to the file ``f`` followed by a newline.
+
+  **Example**::
+
+       fmt::println(stderr, "Don't {}!", "panic");
+  \endrst
+ */
+template <typename... T>
+FMT_INLINE void println(std::FILE* f, format_string<T...> fmt, T&&... args) {
+  return fmt::print(f, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+/**
+  \rst
+  Formats ``args`` according to specifications in ``fmt`` and writes the output
+  to ``stdout`` followed by a newline.
+
+  **Example**::
+
+       fmt::println("Elapsed time: {0:.2f} seconds", 1.23);
+  \endrst
+ */
+template <typename... T>
+FMT_INLINE void println(format_string<T...> fmt, T&&... args) {
+  return fmt::println(stdout, fmt, std::forward<T>(args)...);
+}
+
 FMT_MODULE_EXPORT_END
 FMT_GCC_PRAGMA("GCC pop_options")
 FMT_END_NAMESPACE
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index 86ec47e1..d3bb432c 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -232,6 +232,19 @@ void print(std::wostream& os,
   vprint(os, fmt, fmt::make_format_args<buffer_context<wchar_t>>(args...));
 }
 
+FMT_MODULE_EXPORT template <typename... T>
+void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
+  print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+FMT_MODULE_EXPORT
+template <typename... Args>
+void println(std::wostream& os,
+             basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
+             Args&&... args) {
+  print(os, L"{}\n", fmt::format(fmt, std::forward<Args>(args)...));
+}
+
 FMT_END_NAMESPACE
 
 #endif  // FMT_OSTREAM_H_
diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
index 5b0cf4d4..5a57c519 100644
--- a/include/fmt/xchar.h
+++ b/include/fmt/xchar.h
@@ -238,6 +238,15 @@ template <typename... T> void print(wformat_string<T...> fmt, T&&... args) {
   return vprint(wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
+template <typename... T>
+void println(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
+  return print(f, L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+template <typename... T> void println(wformat_string<T...> fmt, T&&... args) {
+  return print(L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
 /**
   Converts *value* to ``std::wstring`` using the default format for type *T*.
  */
diff --git a/test/format-test.cc b/test/format-test.cc
index c1d97766..eaf84c52 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1778,6 +1778,9 @@ TEST(format_test, print) {
   EXPECT_WRITE(stdout, fmt::print("Don't {}!", "panic"), "Don't panic!");
   EXPECT_WRITE(stderr, fmt::print(stderr, "Don't {}!", "panic"),
                "Don't panic!");
+  EXPECT_WRITE(stdout, fmt::println("Don't {}!", "panic"), "Don't panic!\n");
+  EXPECT_WRITE(stderr, fmt::println(stderr, "Don't {}!", "panic"),
+               "Don't panic!\n");
 }
 
 TEST(format_test, variadic) {
diff --git a/test/ostream-test.cc b/test/ostream-test.cc
index 4ba1279f..b9a6b352 100644
--- a/test/ostream-test.cc
+++ b/test/ostream-test.cc
@@ -106,9 +106,17 @@ TEST(ostream_test, empty_custom_output) {
 }
 
 TEST(ostream_test, print) {
-  std::ostringstream os;
-  fmt::print(os, "Don't {}!", "panic");
-  EXPECT_EQ("Don't panic!", os.str());
+  {
+    std::ostringstream os;
+    fmt::print(os, "Don't {}!", "panic");
+    EXPECT_EQ("Don't panic!", os.str());
+  }
+
+  {
+    std::ostringstream os;
+    fmt::println(os, "Don't {}!", "panic");
+    EXPECT_EQ("Don't panic!\n", os.str());
+  }
 }
 
 TEST(ostream_test, write_to_ostream) {
diff --git a/test/xchar-test.cc b/test/xchar-test.cc
index 34af6e4f..1deab2d0 100644
--- a/test/xchar-test.cc
+++ b/test/xchar-test.cc
@@ -210,7 +210,10 @@ TEST(xchar_test, named_arg_udl) {
 
 TEST(xchar_test, print) {
   // Check that the wide print overload compiles.
-  if (fmt::detail::const_check(false)) fmt::print(L"test");
+  if (fmt::detail::const_check(false)) {
+    fmt::print(L"test");
+    fmt::println(L"test");
+  }
 }
 
 TEST(xchar_test, join) {
@@ -382,9 +385,17 @@ TEST(xchar_test, color) {
 
 TEST(xchar_test, ostream) {
 #if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 409
-  std::wostringstream wos;
-  fmt::print(wos, L"Don't {}!", L"panic");
-  EXPECT_EQ(wos.str(), L"Don't panic!");
+  {
+    std::wostringstream wos;
+    fmt::print(wos, L"Don't {}!", L"panic");
+    EXPECT_EQ(wos.str(), L"Don't panic!");
+  }
+
+  {
+    std::wostringstream wos;
+    fmt::println(wos, L"Don't {}!", L"panic");
+    EXPECT_EQ(wos.str(), L"Don't panic!\n");
+  }
 #endif
 }