Implement default chrono formatting

include/fmt/chrono.h

@@ -48,6 +48,16 @@ FMT_CONSTEXPR const Char *parse_chrono_format(
     case '%':
       handler.on_text(ptr - 1, ptr);
       break;
+    case 'n': {
+      const char newline[] = "\n";
+      handler.on_text(newline, newline + 1);
+      break;
+    }
+    case 't': {
+      const char tab[] = "\t";
+      handler.on_text(tab, tab + 1);
+      break;
+    }
     // Day of the week:
     case 'a':
       handler.on_abbr_weekday();
@@ -83,13 +93,13 @@ FMT_CONSTEXPR const Char *parse_chrono_format(
       break;
     // Other:
     case 'c':
-      handler.on_std_datetime();
+      handler.on_datetime(numeric_system::standard);
       break;
     case 'x':
-      handler.on_loc_date();
+      handler.on_loc_date(numeric_system::standard);
       break;
     case 'X':
-      handler.on_loc_time();
+      handler.on_loc_time(numeric_system::standard);
       break;
     case 'D':
       handler.on_us_date();
@@ -103,7 +113,38 @@ FMT_CONSTEXPR const Char *parse_chrono_format(
     case 'R':
       handler.on_24_hour_time();
       break;
-    // Alternative numeric system:
+    case 'T':
+      handler.on_iso_time();
+      break;
+    case 'p':
+      handler.on_am_pm();
+      break;
+    case 'z':
+      handler.on_utc_offset();
+      break;
+    case 'Z':
+      handler.on_tz_name();
+      break;
+    // Alternative representation:
+    case 'E': {
+      if (ptr == end)
+        throw format_error("invalid format");
+      c = *ptr++;
+      switch (c) {
+      case 'c':
+        handler.on_datetime(numeric_system::alternative);
+        break;
+      case 'x':
+        handler.on_loc_date(numeric_system::alternative);
+        break;
+      case 'X':
+        handler.on_loc_time(numeric_system::alternative);
+        break;
+      default:
+        throw format_error("invalid format");
+      }
+      break;
+    }
     case 'O':
       if (ptr == end)
         throw format_error("invalid format");
@@ -127,9 +168,12 @@ FMT_CONSTEXPR const Char *parse_chrono_format(
       case 'S':
         handler.on_second(numeric_system::alternative);
         break;
+      default:
+        throw format_error("invalid format");
       }
       break;
-      // TODO: parse more format specifiers
+    default:
+      throw format_error("invalid format");
     }
     begin = ptr;
   }
@@ -139,25 +183,31 @@ FMT_CONSTEXPR const Char *parse_chrono_format(
 }
 
 struct chrono_format_checker {
+  void report_no_date() { throw format_error("no date"); }
+
   template <typename Char>
   void on_text(const Char *, const Char *) {}
-  void on_abbr_weekday() {}
-  void on_full_weekday() {}
-  void on_dec0_weekday(numeric_system) {}
-  void on_dec1_weekday(numeric_system) {}
-  void on_abbr_month() {}
-  void on_full_month() {}
+  void on_abbr_weekday() { report_no_date(); }
+  void on_full_weekday() { report_no_date(); }
+  void on_dec0_weekday(numeric_system) { report_no_date(); }
+  void on_dec1_weekday(numeric_system) { report_no_date(); }
+  void on_abbr_month() { report_no_date(); }
+  void on_full_month() { report_no_date(); }
   void on_24_hour(numeric_system) {}
   void on_12_hour(numeric_system) {}
   void on_minute(numeric_system) {}
   void on_second(numeric_system) {}
-  void on_std_datetime() {}
-  void on_loc_date() {}
-  void on_loc_time() {}
-  void on_us_date() {}
-  void on_iso_date() {}
+  void on_datetime(numeric_system) { report_no_date(); }
+  void on_loc_date(numeric_system) { report_no_date(); }
+  void on_loc_time(numeric_system) { report_no_date(); }
+  void on_us_date() { report_no_date(); }
+  void on_iso_date() { report_no_date(); }
   void on_12_hour_time() {}
   void on_24_hour_time() {}
+  void on_iso_time() {}
+  void on_am_pm() {}
+  void on_utc_offset() { report_no_date(); }
+  void on_tz_name() { report_no_date(); }
 };
 
 template <typename Int>
@@ -197,18 +247,6 @@ struct chrono_formatter {
     return time;
   }
 
-  std::tm datetime() const {
-    auto t = time();
-    t.tm_mday = 1;
-    return t;
-  }
-
-  std::tm date() const {
-    auto t = std::tm();
-    t.tm_mday = 1;
-    return t;
-  }
-
   void write(int value, int width) {
     typedef typename int_traits<int>::main_type main_type;
     main_type n = to_unsigned(value);
@@ -232,12 +270,20 @@ struct chrono_formatter {
     std::copy(begin, end, out);
   }
 
+  // These are not implemented because durations don't have date information.
   void on_abbr_weekday() {}
   void on_full_weekday() {}
   void on_dec0_weekday(numeric_system) {}
   void on_dec1_weekday(numeric_system) {}
   void on_abbr_month() {}
   void on_full_month() {}
+  void on_datetime(numeric_system) {}
+  void on_loc_date(numeric_system) {}
+  void on_loc_time(numeric_system) {}
+  void on_us_date() {}
+  void on_iso_date() {}
+  void on_utc_offset() {}
+  void on_tz_name() {}
 
   void on_24_hour(numeric_system ns) {
     if (ns == numeric_system::standard)
@@ -277,26 +323,6 @@ struct chrono_formatter {
     format_localized(time, "%OS");
   }
 
-  void on_std_datetime() { format_localized(datetime(), "%c"); }
-  void on_loc_date() { format_localized(date(), "%x"); }
-  void on_loc_time() { format_localized(datetime(), "%X"); }
-
-  void on_us_date() {
-    write(1, 2);
-    *out++ = '/';
-    write(0, 2);
-    *out++ = '/';
-    write(0, 2);
-  }
-
-  void on_iso_date() {
-    write(1, 4);
-    *out++ = '-';
-    write(0, 2);
-    *out++ = '-';
-    write(0, 2);
-  }
-
   void on_12_hour_time() { format_localized(time(), "%r"); }
 
   void on_24_hour_time() {
@@ -304,9 +330,44 @@ struct chrono_formatter {
     *out++ = ':';
     write(minute(), 2);
   }
+
+  void on_iso_time() {
+    on_24_hour_time();
+    *out++ = ':';
+    write(second(), 2);
+  }
+
+  void on_am_pm() { format_localized(time(), "%p"); }
 };
 }  // namespace internal
 
+template <typename Period> FMT_CONSTEXPR const char *get_units() {
+  return FMT_NULL;
+}
+template <> FMT_CONSTEXPR const char *get_units<std::atto>() { return "as"; }
+template <> FMT_CONSTEXPR const char *get_units<std::femto>() { return "fs"; }
+template <> FMT_CONSTEXPR const char *get_units<std::pico>() { return "ps"; }
+template <> FMT_CONSTEXPR const char *get_units<std::nano>() { return "ns"; }
+template <> FMT_CONSTEXPR const char *get_units<std::micro>() { return "µs"; }
+template <> FMT_CONSTEXPR const char *get_units<std::milli>() { return "ms"; }
+template <> FMT_CONSTEXPR const char *get_units<std::centi>() { return "cs"; }
+template <> FMT_CONSTEXPR const char *get_units<std::deci>() { return "ds"; }
+template <> FMT_CONSTEXPR const char *get_units<std::ratio<1>>() { return "s"; }
+template <> FMT_CONSTEXPR const char *get_units<std::deca>() { return "das"; }
+template <> FMT_CONSTEXPR const char *get_units<std::hecto>() { return "hs"; }
+template <> FMT_CONSTEXPR const char *get_units<std::kilo>() { return "ks"; }
+template <> FMT_CONSTEXPR const char *get_units<std::mega>() { return "Ms"; }
+template <> FMT_CONSTEXPR const char *get_units<std::giga>() { return "Gs"; }
+template <> FMT_CONSTEXPR const char *get_units<std::tera>() { return "Ts"; }
+template <> FMT_CONSTEXPR const char *get_units<std::peta>() { return "Ps"; }
+template <> FMT_CONSTEXPR const char *get_units<std::exa>() { return "Es"; }
+template <> FMT_CONSTEXPR const char *get_units<std::ratio<60>>() {
+  return "m";
+}
+template <> FMT_CONSTEXPR const char *get_units<std::ratio<3600>>() {
+  return "h";
+}
+
 template <typename Rep, typename Period, typename Char>
 struct formatter<std::chrono::duration<Rep, Period>, Char> {
   mutable basic_string_view<Char> format_str;
@@ -323,10 +384,19 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
   template <typename FormatContext>
   auto format(const duration &d, FormatContext &ctx)
       -> decltype(ctx.out()) {
+    auto begin = format_str.begin(), end = format_str.end();
+    if (begin == end || *begin == '}') {
+      if (const char *unit = get_units<Period>())
+        return format_to(ctx.out(), "{}{}", d.count(), unit);
+      if (Period::den == 1)
+        return format_to(ctx.out(), "{}[{}s]", d.count(), Period::num);
+      return format_to(ctx.out(), "{}[{}/{}s]",
+                       d.count(), Period::num, Period::den);
+    }
     internal::chrono_formatter<FormatContext> f(ctx);
     f.s = std::chrono::duration_cast<std::chrono::seconds>(d);
     f.ms = std::chrono::duration_cast<std::chrono::milliseconds>(d - f.s);
-    parse_chrono_format(format_str.begin(), format_str.end(), f);
+    parse_chrono_format(begin, end, f);
     return f.out;
   }
 };

test/chrono-test.cc

@@ -6,7 +6,7 @@
 // For the license information refer to format.h.
 
 #include "fmt/chrono.h"
-#include "gtest.h"
+#include "gtest-extra.h"
 
 #include <iomanip>
 
@@ -49,7 +49,52 @@ std::string format_tm(const std::tm &time, const char *spec,
               fmt::format(loc, "{:" spec "}", duration)); \
   }
 
-TEST(ChronoTest, Format) {
+TEST(ChronoTest, FormatDefault) {
+  EXPECT_EQ("42s", fmt::format("{}", std::chrono::seconds(42)));
+  EXPECT_EQ("42as",
+            fmt::format("{}", std::chrono::duration<int, std::atto>(42)));
+  EXPECT_EQ("42fs",
+            fmt::format("{}", std::chrono::duration<int, std::femto>(42)));
+  EXPECT_EQ("42ps",
+            fmt::format("{}", std::chrono::duration<int, std::pico>(42)));
+  EXPECT_EQ("42ns", fmt::format("{}", std::chrono::nanoseconds(42)));
+  EXPECT_EQ("42µs", fmt::format("{}", std::chrono::microseconds(42)));
+  EXPECT_EQ("42ms", fmt::format("{}", std::chrono::milliseconds(42)));
+  EXPECT_EQ("42cs",
+            fmt::format("{}", std::chrono::duration<int, std::centi>(42)));
+  EXPECT_EQ("42ds",
+            fmt::format("{}", std::chrono::duration<int, std::deci>(42)));
+  EXPECT_EQ("42s", fmt::format("{}", std::chrono::seconds(42)));
+  EXPECT_EQ("42das",
+            fmt::format("{}", std::chrono::duration<int, std::deca>(42)));
+  EXPECT_EQ("42hs",
+            fmt::format("{}", std::chrono::duration<int, std::hecto>(42)));
+  EXPECT_EQ("42ks",
+            fmt::format("{}", std::chrono::duration<int, std::kilo>(42)));
+  EXPECT_EQ("42Ms",
+            fmt::format("{}", std::chrono::duration<int, std::mega>(42)));
+  EXPECT_EQ("42Gs",
+            fmt::format("{}", std::chrono::duration<int, std::giga>(42)));
+  EXPECT_EQ("42Ts",
+            fmt::format("{}", std::chrono::duration<int, std::tera>(42)));
+  EXPECT_EQ("42Ps",
+            fmt::format("{}", std::chrono::duration<int, std::peta>(42)));
+  EXPECT_EQ("42Es",
+            fmt::format("{}", std::chrono::duration<int, std::exa>(42)));
+  EXPECT_EQ("42m", fmt::format("{}", std::chrono::minutes(42)));
+  EXPECT_EQ("42h", fmt::format("{}", std::chrono::hours(42)));
+  EXPECT_EQ("42[15s]",
+            fmt::format("{}",
+                        std::chrono::duration<int, std::ratio<15, 1>>(42)));
+  EXPECT_EQ("42[15/4s]",
+            fmt::format("{}",
+                        std::chrono::duration<int, std::ratio<15, 4>>(42)));
+}
+
+TEST(ChronoTest, FormatSpecs) {
+  EXPECT_EQ("%", fmt::format("{:%%}", std::chrono::seconds(0)));
+  EXPECT_EQ("\n", fmt::format("{:%n}", std::chrono::seconds(0)));
+  EXPECT_EQ("\t", fmt::format("{:%t}", std::chrono::seconds(0)));
   EXPECT_EQ("00", fmt::format("{:%S}", std::chrono::seconds(0)));
   EXPECT_EQ("00", fmt::format("{:%S}", std::chrono::seconds(60)));
   EXPECT_EQ("42", fmt::format("{:%S}", std::chrono::seconds(42)));
@@ -69,9 +114,34 @@ TEST(ChronoTest, Format) {
   EXPECT_EQ("02", fmt::format("{:%I}", std::chrono::hours(14)));
   EXPECT_EQ("03:25:45",
             fmt::format("{:%H:%M:%S}", std::chrono::seconds(12345)));
-  EXPECT_EQ("01/00/00", fmt::format("{:%D}", std::chrono::seconds()));
-  EXPECT_EQ("0001-00-00", fmt::format("{:%F}", std::chrono::seconds()));
   EXPECT_EQ("03:25", fmt::format("{:%R}", std::chrono::seconds(12345)));
+  EXPECT_EQ("03:25:45", fmt::format("{:%T}", std::chrono::seconds(12345)));
+}
+
+TEST(ChronoTest, InvalidSpecs) {
+  auto sec = std::chrono::seconds(0);
+  EXPECT_THROW_MSG(fmt::format("{:%a}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%A}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%c}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%x}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%Ex}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%X}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%EX}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%D}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%F}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%Ec}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%w}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%u}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%b}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%B}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%z}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%Z}", sec), fmt::format_error, "no date");
+  EXPECT_THROW_MSG(fmt::format("{:%q}", sec), fmt::format_error,
+                   "invalid format");
+  EXPECT_THROW_MSG(fmt::format("{:%Eq}", sec), fmt::format_error,
+                   "invalid format");
+  EXPECT_THROW_MSG(fmt::format("{:%Oq}", sec), fmt::format_error,
+                   "invalid format");
 }
 
 TEST(ChronoTest, Locale) {
@@ -94,8 +164,7 @@ TEST(ChronoTest, Locale) {
   time.tm_hour = 3;
   time.tm_min = 25;
   time.tm_sec = 45;
-  EXPECT_TIME("%c", time, std::chrono::seconds(12345));
-  EXPECT_TIME("%x", time, std::chrono::seconds(12345));
-  EXPECT_TIME("%X", time, std::chrono::seconds(12345));
-  EXPECT_TIME("%r", time, std::chrono::seconds(12345));
+  auto sec = std::chrono::seconds(12345);
+  EXPECT_TIME("%r", time, sec);
+  EXPECT_TIME("%p", time, sec);
 }