LibJS: Begin implementing the relativeTo option of Duration.compare

Author: https://github.com/trflynn89
Commit: 0befd52725
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2513
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibJS/Runtime/Temporal/Duration.cpp

@@ -17,6 +17,7 @@
 #include <LibJS/Runtime/Temporal/Duration.h>
 #include <LibJS/Runtime/Temporal/DurationConstructor.h>
 #include <LibJS/Runtime/Temporal/Instant.h>
+#include <LibJS/Runtime/Temporal/PlainDate.h>
 #include <LibJS/Runtime/Temporal/PlainDateTime.h>
 #include <LibJS/Runtime/Temporal/TimeZone.h>
 #include <LibJS/Runtime/VM.h>
@@ -796,6 +797,32 @@ i8 time_duration_sign(TimeDuration const& time_duration)
     return 0;
 }
 
+// 7.5.29 DateDurationDays ( dateDuration, plainRelativeTo ), https://tc39.es/proposal-temporal/#sec-temporal-datedurationdays
+ThrowCompletionOr<double> date_duration_days(VM& vm, DateDuration const& date_duration, PlainDate const& plain_relative_to)
+{
+    // 1. Let yearsMonthsWeeksDuration be ! AdjustDateDurationRecord(dateDuration, 0).
+    auto years_months_weeks_duration = MUST(adjust_date_duration_record(vm, date_duration, 0));
+
+    // 2. If DateDurationSign(yearsMonthsWeeksDuration) = 0, return dateDuration.[[Days]].
+    if (date_duration_sign(years_months_weeks_duration) == 0)
+        return date_duration.days;
+
+    // 3. Let later be ? CalendarDateAdd(plainRelativeTo.[[Calendar]], plainRelativeTo.[[ISODate]], yearsMonthsWeeksDuration, CONSTRAIN).
+    auto later = TRY(calendar_date_add(vm, plain_relative_to.calendar(), plain_relative_to.iso_date(), years_months_weeks_duration, Overflow::Constrain));
+
+    // 4. Let epochDays1 be ISODateToEpochDays(plainRelativeTo.[[ISODate]].[[Year]], plainRelativeTo.[[ISODate]].[[Month]] - 1, plainRelativeTo.[[ISODate]].[[Day]]).
+    auto epoch_days1 = iso_date_to_epoch_days(plain_relative_to.iso_date().year, plain_relative_to.iso_date().month - 1, plain_relative_to.iso_date().day);
+
+    // 5. Let epochDays2 be ISODateToEpochDays(later.[[Year]], later.[[Month]] - 1, later.[[Day]]).
+    auto epoch_days2 = iso_date_to_epoch_days(later.year, later.month - 1, later.day);
+
+    // 6. Let yearsMonthsWeeksInDays be epochDays2 - epochDays1.
+    auto years_months_weeks_in_days = epoch_days2 - epoch_days1;
+
+    // 7. Return dateDuration.[[Days]] + yearsMonthsWeeksInDays.
+    return date_duration.days + years_months_weeks_in_days;
+}
+
 // 7.5.30 RoundTimeDuration ( timeDuration, increment, unit, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-roundtimeduration
 ThrowCompletionOr<TimeDuration> round_time_duration(VM& vm, TimeDuration const& time_duration, Crypto::UnsignedBigInteger const& increment, Unit unit, RoundingMode rounding_mode)
 {

Libraries/LibJS/Runtime/Temporal/Duration.h

@@ -134,6 +134,7 @@ i8 compare_time_duration(TimeDuration const&, TimeDuration const&);
 TimeDuration time_duration_from_epoch_nanoseconds_difference(TimeDuration const&, TimeDuration const&);
 ThrowCompletionOr<TimeDuration> round_time_duration_to_increment(VM&, TimeDuration const&, Crypto::UnsignedBigInteger const& increment, RoundingMode);
 i8 time_duration_sign(TimeDuration const&);
+ThrowCompletionOr<double> date_duration_days(VM&, DateDuration const&, PlainDate const&);
 ThrowCompletionOr<TimeDuration> round_time_duration(VM&, TimeDuration const&, Crypto::UnsignedBigInteger const& increment, Unit, RoundingMode);
 ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM&, i8 sign, InternalDuration const&, TimeDuration const& dest_epoch_ns, ISODateTime const&, Optional<StringView> time_zone, StringView calendar, u64 increment, Unit, RoundingMode);
 ThrowCompletionOr<DurationNudgeResult> nudge_to_zoned_time(VM&, i8 sign, InternalDuration const&, ISODateTime const&, StringView time_zone, StringView calendar, u64 increment, Unit, RoundingMode);

Libraries/LibJS/Runtime/Temporal/DurationConstructor.cpp

@@ -133,7 +133,7 @@ JS_DEFINE_NATIVE_FUNCTION(DurationConstructor::compare)
 
     // 6. Let zonedRelativeTo be relativeToRecord.[[ZonedRelativeTo]].
     // 7. Let plainRelativeTo be relativeToRecord.[[PlainRelativeTo]].
-    auto [zoned_relative_to, plain_relative_to] = relative_to_record;
+    auto [plain_relative_to, zoned_relative_to] = relative_to_record;
 
     // 8. Let largestUnit1 be DefaultTemporalLargestUnit(one).
     auto largest_unit1 = default_temporal_largest_unit(one);
@@ -169,8 +169,12 @@ JS_DEFINE_NATIVE_FUNCTION(DurationConstructor::compare)
         if (!plain_relative_to)
             return vm.throw_completion<RangeError>(ErrorType::TemporalMissingStartingPoint, "calendar units");
 
-        // FIXME: b. Let days1 be ? DateDurationDays(duration1.[[Date]], plainRelativeTo).
-        // FIXME: c. Let days2 be ? DateDurationDays(duration2.[[Date]], plainRelativeTo).
+        // b. Let days1 be ? DateDurationDays(duration1.[[Date]], plainRelativeTo).
+        days1 = TRY(date_duration_days(vm, duration1.date, *plain_relative_to));
+
+        // c. Let days2 be ? DateDurationDays(duration2.[[Date]], plainRelativeTo).
+        days2 = TRY(date_duration_days(vm, duration2.date, *plain_relative_to));
+
     }
     // 14. Else,
     else {

Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.compare.js

@@ -27,6 +27,26 @@ describe("correct behavior", () => {
         const duration2 = "P2D";
         checkCommonResults(duration1, duration2);
     });
+
+    test("relative to plain date", () => {
+        const oneMonth = new Temporal.Duration(0, 1);
+        const thirtyDays = new Temporal.Duration(0, 0, 0, 30);
+
+        let result = Temporal.Duration.compare(oneMonth, thirtyDays, {
+            relativeTo: Temporal.PlainDate.from("2018-04-01"),
+        });
+        expect(result).toBe(0);
+
+        result = Temporal.Duration.compare(oneMonth, thirtyDays, {
+            relativeTo: Temporal.PlainDate.from("2018-03-01"),
+        });
+        expect(result).toBe(1);
+
+        result = Temporal.Duration.compare(oneMonth, thirtyDays, {
+            relativeTo: Temporal.PlainDate.from("2018-02-01"),
+        });
+        expect(result).toBe(-1);
+    });
 });
 
 describe("errors", () => {