Editorial: Abstract days range check into CheckISODaysRange

This pattern is there because of #2729 and #2985. Abstract it into its own
operation, for documentation purposes and because it can disappear after
tc39/ecma262#1087 is fixed.

See: #3005

polyfill/lib/ecmascript.mjs

@@ -1301,9 +1301,7 @@ export function ToTemporalInstant(item) {
     microsecond,
     nanosecond - offsetNanoseconds
   );
-  if (MathAbs(ISODateToEpochDays(balanced.isoDate.year, balanced.isoDate.month - 1, balanced.isoDate.day)) > 1e8) {
-    throw new RangeErrorCtor('date/time value is outside the supported range');
-  }
+  CheckISODaysRange(balanced.isoDate);
   const epochNanoseconds = GetUTCEpochNanoseconds(balanced);
   ValidateEpochNanoseconds(epochNanoseconds);
   return new TemporalInstant(epochNanoseconds);
@@ -1441,17 +1439,13 @@ export function InterpretISODateTimeOffset(
       time.microsecond,
       time.nanosecond - offsetNs
     );
-    if (MathAbs(ISODateToEpochDays(balanced.year, balanced.month - 1, balanced.day)) > 1e8) {
-      throw new RangeErrorCtor('date/time outside of supported range');
-    }
+    CheckISODaysRange(balanced.isoDate);
     const epochNs = GetUTCEpochNanoseconds(balanced);
     ValidateEpochNanoseconds(epochNs);
     return epochNs;
   }
 
-  if (MathAbs(ISODateToEpochDays(isoDate.year, isoDate.month - 1, isoDate.day)) > 1e8) {
-    throw new RangeErrorCtor('date/time outside of supported range');
-  }
+  CheckISODaysRange(isoDate);
   const utcEpochNs = GetUTCEpochNanoseconds(dt);
 
   // "prefer" or "reject"
@@ -1936,19 +1930,13 @@ export function GetPossibleEpochNanoseconds(timeZone, isoDateTime) {
       isoDateTime.time.microsecond,
       isoDateTime.time.nanosecond
     );
-    if (MathAbs(ISODateToEpochDays(balanced.isoDate.year, balanced.isoDate.month - 1, balanced.isoDate.day)) > 1e8) {
-      throw new RangeErrorCtor('date/time value is outside the supported range');
-    }
+    CheckISODaysRange(balanced.isoDate);
     const epochNs = GetUTCEpochNanoseconds(balanced);
     ValidateEpochNanoseconds(epochNs);
     return [epochNs];
   }
 
-  if (
-    MathAbs(ISODateToEpochDays(isoDateTime.isoDate.year, isoDateTime.isoDate.month - 1, isoDateTime.isoDate.day)) > 1e8
-  ) {
-    throw new RangeErrorCtor('date/time value is outside the supported range');
-  }
+  CheckISODaysRange(isoDateTime.isoDate);
   return GetNamedTimeZoneEpochNanoseconds(timeZone, isoDateTime);
 }
 
@@ -2978,6 +2966,16 @@ export function ISODateToEpochDays(y, m, d) {
   return GetUTCEpochMilliseconds(y, m + 1, d, 0, 0, 0, 0) / DAY_MS;
 }
 
+// This is needed before calling GetUTCEpochNanoseconds, because it uses MakeDay
+// which is ill-defined in how it handles large year numbers. If the issue
+// https://github.com/tc39/ecma262/issues/1087 is fixed, this can be removed
+// with no observable changes.
+function CheckISODaysRange({ year, month, day }) {
+  if (MathAbs(ISODateToEpochDays(year, month - 1, day)) > 1e8) {
+    throw new RangeErrorCtor('date/time value is outside the supported range');
+  }
+}
+
 function DifferenceTime(time1, time2) {
   const hours = time2.hour - time1.hour;
   const minutes = time2.minute - time1.minute;

spec/abstractops.html

@@ -108,6 +108,28 @@ <h1>Date Equations</h1>
     <emu-note type="editor"> Note that the operation EpochTimeToMonthInYear(_t_) uses 0-based months unlike rest of Temporal since it's intended to be unified with MonthFromTime(_t_) when the above mentioned issue is fixed.</emu-note>
   </emu-clause>
 
+  <emu-clause id="sec-checkisodaysrange" type="abstract operation">
+    <h1>
+      CheckISODaysRange (
+        _isoDate_: an ISO Date Record,
+      ): either a normal completion containing ~unused~ or a throw completion
+    </h1>
+    <dl class="header">
+      <dt>description</dt>
+      <dd>It checks that the given date is within the range of 10<sup>8</sup> days from the epoch.</dd>
+    </dl>
+    <emu-alg>
+      1. If abs(ISODateToEpochDays(_isoDate_.[[Year]], _isoDate_.[[Month]] - 1, _isoDate_.[[Day]])) > 10<sup>8</sup>, then
+        1. Throw a *RangeError* exception.
+      1. Return ~unused~.
+    </emu-alg>
+    <emu-note type="editor">
+      This operation is solely present to ensure that GetUTCEpochNanoseconds is not called with numbers that are too large.
+      It is distinct from ISODateWithinLimits, which uses GetUTCEpochNanoseconds.
+      This operation can be removed with no observable effect when https://github.com/tc39/ecma262/issues/1087 is fixed.
+    </emu-note>
+  </emu-clause>
+
   <emu-clause id="sec-temporal-units">
     <h1>Units</h1>
     <p>

spec/instant.html

@@ -414,7 +414,7 @@ <h1>
         1. If _parsed_.[[TimeZone]].[[Z]] is *true*, let _offsetNanoseconds_ be 0; otherwise, let _offsetNanoseconds_ be ! ParseDateTimeUTCOffset(_parsed_.[[TimeZone]].[[OffsetString]]).
         1. If _parsed_.[[Time]] is ~start-of-day~, let _time_ be MidnightTimeRecord(); else let _time_ be _parsed_.[[Time]].
         1. Let _balanced_ be BalanceISODateTime(_parsed_.[[Year]], _parsed_.[[Month]], _parsed_.[[Day]], _time_.[[Hour]], _time_.[[Minute]], _time_.[[Second]], _time_.[[Millisecond]], _time_.[[Microsecond]], _time_.[[Nanosecond]] - _offsetNanoseconds_).
-        1. If abs(ISODateToEpochDays(_balanced_.[[ISODate]].[[Year]], _balanced_.[[ISODate]].[[Month]] - 1, _balanced_.[[ISODate]].[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+        1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
         1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
         1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.
         1. Return ! CreateTemporalInstant(_epochNanoseconds_).

spec/timezone.html

@@ -350,11 +350,11 @@ <h1>
         1. Let _parseResult_ be ! ParseTimeZoneIdentifier(_timeZone_).
         1. If _parseResult_.[[OffsetMinutes]] is not ~empty~, then
           1. Let _balanced_ be BalanceISODateTime(_isoDateTime_.[[ISODate]].[[Year]], _isoDateTime_.[[ISODate]].[[Month]], _isoDateTime_.[[ISODate]].[[Day]], _isoDateTime_.[[Time]].[[Hour]], _isoDateTime_.[[Time]].[[Minute]] - _parseResult_.[[OffsetMinutes]], _isoDateTime_.[[Time]].[[Second]], _isoDateTime_.[[Time]].[[Millisecond]], _isoDateTime_.[[Time]].[[Microsecond]], _isoDateTime_.[[Time]].[[Nanosecond]]).
-          1. If abs(ISODateToEpochDays(_balanced_.[[ISODate]].[[Year]], _balanced_.[[ISODate]].[[Month]] - 1, _balanced_.[[ISODate]].[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+          1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
           1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
           1. Let _possibleEpochNanoseconds_ be « _epochNanoseconds_ ».
         1. Else,
-          1. If abs(ISODateToEpochDays(_isoDateTime_.[[ISODate]].[[Year]], _isoDateTime_.[[ISODate]].[[Month]] - 1, _isoDateTime_.[[ISODate]].[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+          1. Perform ? CheckISODaysRange(_isoDateTime_.[[ISODate]]).
           1. Let _possibleEpochNanoseconds_ be GetNamedTimeZoneEpochNanoseconds(_parseResult_.[[Name]], _isoDateTime_).
         1. For each value _epochNanoseconds_ in _possibleEpochNanoseconds_, do
           1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.

spec/zoneddatetime.html

@@ -916,13 +916,13 @@ <h1>
           1. Return ? GetEpochNanosecondsFor(_timeZone_, _isoDateTime_, _disambiguation_).
         1. If _offsetBehaviour_ is ~exact~, or _offsetBehaviour_ is ~option~ and _offsetOption_ is ~use~, then
           1. Let _balanced_ be BalanceISODateTime(_isoDate_.[[Year]], _isoDate_.[[Month]], _isoDate_.[[Day]], _time_.[[Hour]], _time_.[[Minute]], _time_.[[Second]], _time_.[[Millisecond]], _time_.[[Microsecond]], _time_.[[Nanosecond]] - _offsetNanoseconds_).
-          1. If abs(ISODateToEpochDays(_balanced_.[[ISODate]].[[Year]], _balanced_.[[ISODate]].[[Month]] - 1, _balanced_.[[ISODate]].[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+          1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
           1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
           1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.
           1. Return _epochNanoseconds_.
         1. Assert: _offsetBehaviour_ is ~option~.
         1. Assert: _offsetOption_ is ~prefer~ or ~reject~.
-        1. If abs(ISODateToEpochDays(_isoDate_.[[Year]], _isoDate_.[[Month]] - 1, _isoDate_.[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+        1. Perform ? CheckISODaysRange(_isoDate_).
         1. Let _utcEpochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_).
         1. Let _possibleEpochNs_ be ? GetPossibleEpochNanoseconds(_timeZone_, _isoDateTime_).
         1. For each element _candidate_ of _possibleEpochNs_, do