Editorial: Adjust RangeError condition in GetPossibleEpochNanoseconds

Similarly to the previous commit, we must avoid calling GetUTCEpochNanoseconds with dates that are too large because it is ill-defined in ECMA-262 what is supposed to happen. (See tc39/ecma262#1087). Previously to PR #2925, that could not happen because GetPossibleInstantsFor took a PlainDateTime object, but now it takes an ISO Date-Time Record. Note that this is editorial, because IsValidEpochNanoseconds would throw anyway in this case even if GetUTCEpochNanoseconds was fully defined for large inputs.
tc39 · Oct 1, 2024 · fcc0c0f · fcc0c0f
1 parent 43bc062
commit fcc0c0f
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Showing 2 changed files with 30 additions and 7 deletions.
diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
@@ -2098,11 +2098,33 @@ export function GetPossibleEpochNanoseconds(timeZone, isoDateTime) {
   const { year, month, day, hour, minute, second, millisecond, microsecond, nanosecond } = isoDateTime;
   const offsetMinutes = ParseTimeZoneIdentifier(timeZone).offsetMinutes;
   if (offsetMinutes !== undefined) {
-    return [
-      GetUTCEpochNanoseconds(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond).subtract(
-        offsetMinutes * 60e9
-      )
-    ];
+    const balanced = BalanceISODateTime(
+      year,
+      month,
+      day,
+      hour,
+      minute - offsetMinutes,
+      second,
+      millisecond,
+      microsecond,
+      nanosecond
+    );
+    if (MathAbs(ISODateToEpochDays(balanced.year, balanced.month - 1, balanced.day)) > 1e8) {
+      throw new RangeErrorCtor('date/time value is outside the supported range');
+    }
+    const epochNs = GetUTCEpochNanoseconds(
+      balanced.year,
+      balanced.month,
+      balanced.day,
+      balanced.hour,
+      balanced.minute,
+      balanced.second,
+      balanced.millisecond,
+      balanced.microsecond,
+      balanced.nanosecond
+    );
+    ValidateEpochNanoseconds(epochNs);
+    return [epochNs];
   }
 
   return GetNamedTimeZoneEpochNanoseconds(

diff --git a/spec/timezone.html b/spec/timezone.html
@@ -357,8 +357,9 @@ <h1>
       <emu-alg>
         1. Let _parseResult_ be ! ParseTimeZoneIdentifier(_timeZone_).
         1. If _parseResult_.[[OffsetMinutes]] is not ~empty~, then
-          1. Let _offsetNanoseconds_ be _parseResult_.[[OffsetMinutes]] × (60 × 10<sup>9</sup>).
-          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]) - ℤ(_offsetNanoseconds_).
+          1. Let _balanced_ be BalanceISODateTime(_isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]] - _parseResult_.[[OffsetMinutes]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]).
+          1. If abs(ISODateToEpochDays(_balanced_.[[Year]], _balanced_.[[Month]] - 1, _balanced_.[[Day]])) > 10<sup>8</sup>, throw a *RangeError* exception.
+          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_.[[Year]], _balanced_.[[Month]], _balanced_.[[Day]], _balanced_.[[Hour]], _balanced_.[[Minute]], _balanced_.[[Second]], _balanced_.[[Millisecond]], _balanced_.[[Microsecond]], _balanced_.[[Nanosecond]]).
           1. Let _possibleEpochNanoseconds_ be « _epochNanoseconds_ ».
         1. Else,
           1. Let _possibleEpochNanoseconds_ be GetNamedTimeZoneEpochNanoseconds(_parseResult_.[[Name]], _isoDateTime_.[[Year]], _isoDateTime_.[[Month]], _isoDateTime_.[[Day]], _isoDateTime_.[[Hour]], _isoDateTime_.[[Minute]], _isoDateTime_.[[Second]], _isoDateTime_.[[Millisecond]], _isoDateTime_.[[Microsecond]], _isoDateTime_.[[Nanosecond]]).