LibJS+LibUnicode: Return the appropriate time zone name depending on DST

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/4400150cd2d
Pull-request: https://github.com/SerenityOS/serenity/pull/12008
Reviewed-by: https://github.com/linusg ✅

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateUnicodeDateTimeFormat.cpp

@@ -2207,17 +2207,17 @@ static TimeZoneNames const* find_time_zone_names(StringView locale, StringView t
     return &s_time_zones[time_zone_index];
 }
 
-Optional<StringView> get_time_zone_name(StringView locale, StringView time_zone, CalendarPatternStyle style)
+Optional<StringView> get_time_zone_name(StringView locale, StringView time_zone, CalendarPatternStyle style, TimeZone::InDST in_dst)
 {
     if (auto const* data = find_time_zone_names(locale, time_zone); data != nullptr) {
         size_t name_index = 0;
 
         switch (style) {
         case CalendarPatternStyle::Short:
-            name_index = data->short_standard_name;
+            name_index = (in_dst == TimeZone::InDST::No) ? data->short_standard_name : data->short_daylight_name;
             break;
         case CalendarPatternStyle::Long:
-            name_index = data->long_standard_name;
+            name_index = (in_dst == TimeZone::InDST::No) ? data->long_standard_name : data->long_daylight_name;
             break;
         case CalendarPatternStyle::ShortGeneric:
             name_index = data->short_generic_name;

Tests/LibUnicode/TestUnicodeDateTimeFormat.cpp

@@ -80,6 +80,56 @@ TEST_CASE(time_zone_name)
     }
 }
 
+TEST_CASE(time_zone_name_dst)
+{
+    struct TestData {
+        StringView locale;
+        Unicode::CalendarPatternStyle style;
+        StringView time_zone;
+        StringView expected_result;
+    };
+
+    constexpr auto test_data = Array {
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Long, "UTC"sv, "Coordinated Universal Time"sv },
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Short, "UTC"sv, "UTC"sv },
+
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Long, "UTC"sv, "التوقيت العالمي المنسق"sv },
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Short, "UTC"sv, "UTC"sv },
+
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Long, "America/Los_Angeles"sv, "Pacific Daylight Time"sv },
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Short, "America/Los_Angeles"sv, "PDT"sv },
+
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Long, "America/Los_Angeles"sv, "توقيت المحيط الهادي الصيفي"sv },
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Short, "America/Los_Angeles"sv, "غرينتش-٧"sv },
+
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Long, "America/Vancouver"sv, "Pacific Daylight Time"sv },
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Short, "America/Vancouver"sv, "PDT"sv },
+
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Long, "America/Vancouver"sv, "توقيت المحيط الهادي الصيفي"sv },
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Short, "America/Vancouver"sv, "غرينتش-٧"sv },
+
+        // FIXME: This should be "British Summer Time", but the CLDR puts that one name in a section we aren't parsing.
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Long, "Europe/London"sv, "GMT+01:00"sv },
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Short, "Europe/London"sv, "GMT+1"sv },
+
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Long, "Europe/London"sv, "غرينتش+٠١:٠٠"sv },
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Short, "Europe/London"sv, "غرينتش+١"sv },
+
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Long, "Africa/Accra"sv, "Greenwich Mean Time"sv },
+        TestData { "en"sv, Unicode::CalendarPatternStyle::Short, "Africa/Accra"sv, "GMT"sv },
+
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Long, "Africa/Accra"sv, "توقيت غرينتش"sv },
+        TestData { "ar"sv, Unicode::CalendarPatternStyle::Short, "Africa/Accra"sv, "غرينتش"sv },
+    };
+
+    constexpr auto sep_19_2022 = AK::Time::from_seconds(1663553728); // Monday, September 19, 2022 2:15:28 AM
+
+    for (auto const& test : test_data) {
+        auto time_zone = Unicode::format_time_zone(test.locale, test.time_zone, test.style, sep_19_2022);
+        EXPECT_EQ(time_zone, test.expected_result);
+    }
+}
+
 TEST_CASE(format_time_zone_offset)
 {
     constexpr auto jan_1_1833 = AK::Time::from_seconds(-4323283200); // Tuesday, January 1, 1833 12:00:00 AM

Userland/Libraries/LibJS/Runtime/DatePrototype.cpp

@@ -1057,8 +1057,10 @@ String time_zone_string(double time)
     auto tz_name = TimeZone::current_time_zone();
 
     // Most implementations seem to prefer the long-form display name of the time zone. Not super important, but we may as well match that behavior.
-    if (auto long_name = Unicode::get_time_zone_name(Unicode::default_locale(), tz_name, Unicode::CalendarPatternStyle::Long); long_name.has_value())
-        tz_name = long_name.release_value();
+    if (auto maybe_offset = TimeZone::get_time_zone_offset(tz_name, AK::Time::from_milliseconds(time)); maybe_offset.has_value()) {
+        if (auto long_name = Unicode::get_time_zone_name(Unicode::default_locale(), tz_name, Unicode::CalendarPatternStyle::Long, maybe_offset->in_dst); long_name.has_value())
+            tz_name = long_name.release_value();
+    }
 
     // 7. Return the string-concatenation of offsetSign, offsetHour, offsetMin, and tzName.
     return String::formatted("{}{:02}{:02} ({})", offset_sign, offset_hour, offset_min, tz_name);

Userland/Libraries/LibUnicode/DateTimeFormat.cpp

@@ -6,7 +6,6 @@
 
 #include <AK/Array.h>
 #include <AK/StringBuilder.h>
-#include <LibTimeZone/TimeZone.h>
 #include <LibUnicode/DateTimeFormat.h>
 #include <LibUnicode/Locale.h>
 #include <LibUnicode/NumberFormat.h>
@@ -195,10 +194,10 @@ Optional<StringView> __attribute__((weak)) get_calendar_weekday_symbol(StringVie
 Optional<StringView> __attribute__((weak)) get_calendar_day_period_symbol(StringView, StringView, CalendarPatternStyle, DayPeriod) { return {}; }
 Optional<StringView> __attribute__((weak)) get_calendar_day_period_symbol_for_hour(StringView, StringView, CalendarPatternStyle, u8) { return {}; }
 
-Optional<StringView> __attribute__((weak)) get_time_zone_name(StringView, StringView, CalendarPatternStyle) { return {}; }
+Optional<StringView> __attribute__((weak)) get_time_zone_name(StringView, StringView, CalendarPatternStyle, TimeZone::InDST) { return {}; }
 Optional<TimeZoneFormat> __attribute__((weak)) get_time_zone_format(StringView) { return {}; }
 
-static Optional<String> format_time_zone_offset(StringView locale, StringView time_zone, CalendarPatternStyle style, AK::Time time)
+static Optional<String> format_time_zone_offset(StringView locale, CalendarPatternStyle style, i64 offset_seconds)
 {
     auto formats = get_time_zone_format(locale);
     if (!formats.has_value())
@@ -208,21 +207,18 @@ static Optional<String> format_time_zone_offset(StringView locale, StringView ti
     if (!number_system.has_value())
         return {};
 
-    auto offset = TimeZone::get_time_zone_offset(time_zone, time);
-    if (!offset.has_value())
-        return {};
-    if (offset->seconds == 0)
+    if (offset_seconds == 0)
         return formats->gmt_zero_format;
 
-    auto sign = offset->seconds > 0 ? formats->symbol_ahead_sign : formats->symbol_behind_sign;
-    auto separator = offset->seconds > 0 ? formats->symbol_ahead_separator : formats->symbol_behind_separator;
-    offset->seconds = llabs(offset->seconds);
+    auto sign = offset_seconds > 0 ? formats->symbol_ahead_sign : formats->symbol_behind_sign;
+    auto separator = offset_seconds > 0 ? formats->symbol_ahead_separator : formats->symbol_behind_separator;
+    offset_seconds = llabs(offset_seconds);
 
-    auto offset_hours = offset->seconds / 3'600;
-    offset->seconds %= 3'600;
+    auto offset_hours = offset_seconds / 3'600;
+    offset_seconds %= 3'600;
 
-    auto offset_minutes = offset->seconds / 60;
-    offset->seconds %= 60;
+    auto offset_minutes = offset_seconds / 60;
+    offset_seconds %= 60;
 
     StringBuilder builder;
     builder.append(sign);
@@ -231,8 +227,8 @@ static Optional<String> format_time_zone_offset(StringView locale, StringView ti
     // The long format always uses 2-digit hours field and minutes field, with optional 2-digit seconds field.
     case CalendarPatternStyle::LongOffset:
         builder.appendff("{:02}{}{:02}", offset_hours, separator, offset_minutes);
-        if (offset->seconds > 0)
-            builder.appendff("{}{:02}", separator, offset->seconds);
+        if (offset_seconds > 0)
+            builder.appendff("{}{:02}", separator, offset_seconds);
         break;
 
     // The short format is intended for the shortest representation and uses hour fields without leading zero, with optional 2-digit minutes and seconds fields.
@@ -240,8 +236,8 @@ static Optional<String> format_time_zone_offset(StringView locale, StringView ti
         builder.appendff("{}", offset_hours);
         if (offset_minutes > 0) {
             builder.appendff("{}{:02}", separator, offset_minutes);
-            if (offset->seconds > 0)
-                builder.appendff("{}{:02}", separator, offset->seconds);
+            if (offset_seconds > 0)
+                builder.appendff("{}{:02}", separator, offset_seconds);
         }
         break;
 
@@ -257,18 +253,22 @@ static Optional<String> format_time_zone_offset(StringView locale, StringView ti
 // https://unicode.org/reports/tr35/tr35-dates.html#Time_Zone_Format_Terminology
 String format_time_zone(StringView locale, StringView time_zone, CalendarPatternStyle style, AK::Time time)
 {
+    auto offset = TimeZone::get_time_zone_offset(time_zone, time);
+    if (!offset.has_value())
+        return time_zone;
+
     switch (style) {
     case CalendarPatternStyle::Short:
     case CalendarPatternStyle::Long:
     case CalendarPatternStyle::ShortGeneric:
     case CalendarPatternStyle::LongGeneric:
-        if (auto name = get_time_zone_name(locale, time_zone, style); name.has_value())
+        if (auto name = get_time_zone_name(locale, time_zone, style, offset->in_dst); name.has_value())
             return *name;
         break;
 
     case CalendarPatternStyle::ShortOffset:
     case CalendarPatternStyle::LongOffset:
-        return format_time_zone_offset(locale, time_zone, style, time).value_or(time_zone);
+        return format_time_zone_offset(locale, style, offset->seconds).value_or(time_zone);
 
     default:
         VERIFY_NOT_REACHED();

Userland/Libraries/LibUnicode/DateTimeFormat.h

@@ -12,6 +12,7 @@
 #include <AK/Time.h>
 #include <AK/Types.h>
 #include <AK/Vector.h>
+#include <LibTimeZone/TimeZone.h>
 #include <LibUnicode/Forward.h>
 
 namespace Unicode {
@@ -210,7 +211,7 @@ Optional<StringView> get_calendar_day_period_symbol(StringView locale, StringVie
 Optional<StringView> get_calendar_day_period_symbol_for_hour(StringView locale, StringView calendar, CalendarPatternStyle style, u8 hour);
 
 String format_time_zone(StringView locale, StringView time_zone, CalendarPatternStyle style, AK::Time time);
-Optional<StringView> get_time_zone_name(StringView locale, StringView time_zone, CalendarPatternStyle style);
+Optional<StringView> get_time_zone_name(StringView locale, StringView time_zone, CalendarPatternStyle style, TimeZone::InDST in_dst);
 Optional<TimeZoneFormat> get_time_zone_format(StringView locale);
 
 }