LibTimeZone: Add an API to retrieve a list of all known IANA time zones

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/da27937144f
Pull-request: https://github.com/SerenityOS/serenity/pull/12026
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/linusg

Meta/Lagom/Tools/CodeGenerators/LibTimeZone/GenerateTimeZoneData.cpp

@@ -524,6 +524,22 @@ Optional<Offset> get_time_zone_offset(TimeZone time_zone, AK::Time time)
     return dst_offset;
 }
 
+Span<StringView const> all_time_zones()
+{
+    static constexpr auto all_time_zones = Array {
+        )~~~");
+
+    for (auto const& time_zone : time_zone_data.time_zone_names) {
+        generator.set("time_zone", time_zone);
+        generator.append("\"@time_zone@\"sv, ");
+    }
+
+    generator.append(R"~~~(
+    };
+
+    return all_time_zones;
+}
+
 }
 )~~~");
 

Userland/Libraries/LibTimeZone/TimeZone.cpp

@@ -31,6 +31,16 @@ StringView current_time_zone()
     return canonicalize_time_zone(tzname[0]).value_or("UTC"sv);
 }
 
+Span<StringView const> __attribute__((weak)) all_time_zones()
+{
+#if !ENABLE_TIME_ZONE_DATA
+    static constexpr auto utc = Array { "UTC"sv };
+    return utc;
+#else
+    return {};
+#endif
+}
+
 Optional<TimeZone> __attribute__((weak)) time_zone_from_string([[maybe_unused]] StringView time_zone)
 {
 #if !ENABLE_TIME_ZONE_DATA

Userland/Libraries/LibTimeZone/TimeZone.h

@@ -25,6 +25,7 @@ struct Offset {
 };
 
 StringView current_time_zone();
+Span<StringView const> all_time_zones();
 
 Optional<TimeZone> time_zone_from_string(StringView time_zone);
 StringView time_zone_to_string(TimeZone time_zone);