Add a formatter specialization for std::error_code.

fmtlib · May 8, 2021 · 41ebf7f · 41ebf7f
1 parent 84feeb0
commit 41ebf7f
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diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -3061,6 +3061,24 @@ template <> struct formatter<bytes> {
   }
 };
 
+// A formatter specialization for std::error_code.
+template <typename Char> struct formatter<std::error_code, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const std::error_code& ec, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    out = detail::write<Char>(out, ec.category().name());
+    out = detail::write<Char>(out, Char(':'));
+    out = detail::write<Char>(out, ec.value());
+    return out;
+  }
+};
+
 template <typename It, typename Sentinel, typename Char>
 struct arg_join : detail::view {
   It begin;

diff --git a/test/compile-test.cc b/test/compile-test.cc
@@ -192,6 +192,30 @@ TEST(compile_test, format_to_n) {
   EXPECT_STREQ("2a", buffer);
 }
 
+TEST(compile_test, format_std_error_code) {
+  EXPECT_EQ("generic:42",
+            fmt::format(FMT_COMPILE("{0}"),
+                        std::error_code(42, std::generic_category())));
+  EXPECT_EQ("system:42",
+            fmt::format(FMT_COMPILE("{0}"),
+                        std::error_code(42, std::system_category())));
+  EXPECT_EQ("system:-42",
+            fmt::format(FMT_COMPILE("{0}"),
+                        std::error_code(-42, std::system_category())));
+}
+
+TEST(compile_test, format_std_error_code_wide) {
+  EXPECT_EQ(L"generic:42",
+            fmt::format(FMT_COMPILE(L"{0}"),
+                        std::error_code(42, std::generic_category())));
+  EXPECT_EQ(L"system:42",
+            fmt::format(FMT_COMPILE(L"{0}"),
+                        std::error_code(42, std::system_category())));
+  EXPECT_EQ(L"system:-42",
+            fmt::format(FMT_COMPILE(L"{0}"),
+                        std::error_code(-42, std::system_category())));
+}
+
 TEST(compile_test, formatted_size) {
   EXPECT_EQ(2, fmt::formatted_size(FMT_COMPILE("{0}"), 42));
   EXPECT_EQ(5, fmt::formatted_size(FMT_COMPILE("{0:<4.2f}"), 42.0));

diff --git a/test/format-test.cc b/test/format-test.cc
@@ -2494,6 +2494,24 @@ TEST(format_test, test_formatters_enabled) {
                            const wchar_t*, std::wstring, std::nullptr_t>();
 }
 
+TEST(format_test, format_std_error_code) {
+  EXPECT_EQ("generic:42",
+            fmt::format("{0}", std::error_code(42, std::generic_category())));
+  EXPECT_EQ("system:42",
+            fmt::format("{0}", std::error_code(42, std::system_category())));
+  EXPECT_EQ("system:-42",
+            fmt::format("{0}", std::error_code(-42, std::system_category())));
+}
+
+TEST(format_test, format_std_error_code_wide) {
+  EXPECT_EQ(L"generic:42",
+            fmt::format(L"{0}", std::error_code(42, std::generic_category())));
+  EXPECT_EQ(L"system:42",
+            fmt::format(L"{0}", std::error_code(42, std::system_category())));
+  EXPECT_EQ(L"system:-42",
+            fmt::format(L"{0}", std::error_code(-42, std::system_category())));
+}
+
 TEST(format_int_test, data) {
   fmt::format_int format_int(42);
   EXPECT_EQ("42", std::string(format_int.data(), format_int.size()));