Implement println (#3267)

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

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_

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*.
  */

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) {

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) {

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
 }