Editorial: Simplify object snapshotting

polyfill/lib/calendar.mjs

@@ -111,12 +111,8 @@ export class Calendar {
   }
   mergeFields(fields, additionalFields) {
     if (!ES.IsTemporalCalendar(this)) throw new TypeError('invalid receiver');
-    fields = ES.ToObject(fields);
-    const fieldsCopy = ObjectCreate(null);
-    ES.CopyDataProperties(fieldsCopy, fields, [], [undefined]);
-    additionalFields = ES.ToObject(additionalFields);
-    const additionalFieldsCopy = ObjectCreate(null);
-    ES.CopyDataProperties(additionalFieldsCopy, additionalFields, [], [undefined]);
+    const fieldsCopy = ES.SnapshotOwnProperties(fields, null, [], [undefined]);
+    const additionalFieldsCopy = ES.SnapshotOwnProperties(additionalFields, null, [], [undefined]);
     const additionalKeys = ReflectOwnKeys(additionalFieldsCopy);
     const overriddenKeys = impl[GetSlot(this, CALENDAR_ID)].fieldKeysToIgnore(additionalKeys);
     const merged = ObjectCreate(null);

polyfill/lib/ecmascript.mjs

@@ -3815,7 +3815,7 @@ export function DifferenceISODateTime(
   const date1 = CreateTemporalDate(y1, mon1, d1, calendar);
   const date2 = CreateTemporalDate(y2, mon2, d2, calendar);
   const dateLargestUnit = LargerOfTwoTemporalUnits('day', largestUnit);
-  const untilOptions = CopyOptions(options);
+  const untilOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   untilOptions.largestUnit = dateLargestUnit;
   const untilResult = CalendarDateUntil(calendar, date1, date2, untilOptions);
   const years = GetSlot(untilResult, YEARS);
@@ -3951,7 +3951,7 @@ export function DifferenceTemporalInstant(operation, instant, other, options) {
   const sign = operation === 'since' ? -1 : 1;
   other = ToTemporalInstant(other);
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'time', [], 'nanosecond', 'second');
 
   const onens = GetSlot(instant, EPOCHNANOSECONDS);
@@ -3986,7 +3986,7 @@ export function DifferenceTemporalPlainDate(operation, plainDate, other, options
   const otherCalendar = GetSlot(other, CALENDAR);
   ThrowIfCalendarsNotEqual(calendar, otherCalendar, 'compute difference between dates');
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'date', [], 'day', 'day');
   resolvedOptions.largestUnit = settings.largestUnit;
 
@@ -4026,7 +4026,7 @@ export function DifferenceTemporalPlainDateTime(operation, plainDateTime, other,
   const otherCalendar = GetSlot(other, CALENDAR);
   ThrowIfCalendarsNotEqual(calendar, otherCalendar, 'compute difference between dates');
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'datetime', [], 'nanosecond', 'day');
 
   let { years, months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds } =
@@ -4101,7 +4101,7 @@ export function DifferenceTemporalPlainTime(operation, plainTime, other, options
   const sign = operation === 'since' ? -1 : 1;
   other = ToTemporalTime(other);
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'time', [], 'nanosecond', 'hour');
 
   let { hours, minutes, seconds, milliseconds, microseconds, nanoseconds } = DifferenceTime(
@@ -4165,7 +4165,7 @@ export function DifferenceTemporalPlainYearMonth(operation, yearMonth, other, op
   const otherCalendar = GetSlot(other, CALENDAR);
   ThrowIfCalendarsNotEqual(calendar, otherCalendar, 'compute difference between months');
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'date', ['week', 'day'], 'month', 'year');
   resolvedOptions.largestUnit = settings.largestUnit;
 
@@ -4209,7 +4209,7 @@ export function DifferenceTemporalZonedDateTime(operation, zonedDateTime, other,
   const otherCalendar = GetSlot(other, CALENDAR);
   ThrowIfCalendarsNotEqual(calendar, otherCalendar, 'compute difference between dates');
 
-  const resolvedOptions = CopyOptions(options);
+  const resolvedOptions = SnapshotOwnProperties(GetOptionsObject(options), null);
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'datetime', [], 'nanosecond', 'hour');
   resolvedOptions.largestUnit = settings.largestUnit;
 
@@ -4744,7 +4744,7 @@ export function AddDurationToOrSubtractDurationFromPlainYearMonth(operation, yea
   const calendar = GetSlot(yearMonth, CALENDAR);
   const fieldNames = CalendarFields(calendar, ['monthCode', 'year']);
   const fields = PrepareTemporalFields(yearMonth, fieldNames, []);
-  const fieldsCopy = CopyOptions(fields);
+  const fieldsCopy = SnapshotOwnProperties(GetOptionsObject(fields), null);
   fields.day = 1;
   let startDate = CalendarDateFromFields(calendar, fields);
   const sign = DurationSign(years, months, weeks, days, 0, 0, 0, 0, 0, 0);
@@ -4759,7 +4759,7 @@ export function AddDurationToOrSubtractDurationFromPlainYearMonth(operation, yea
     startDate = CalendarDateFromFields(calendar, fieldsCopy);
   }
   const durationToAdd = new Duration(years, months, weeks, days, 0, 0, 0, 0, 0, 0);
-  const optionsCopy = CopyOptions(options);
+  const optionsCopy = SnapshotOwnProperties(GetOptionsObject(options), null);
   const addedDate = CalendarDateAdd(calendar, startDate, durationToAdd, options, dateAdd);
   const addedDateFields = PrepareTemporalFields(addedDate, fieldNames, []);
 
@@ -5412,10 +5412,10 @@ export function GetOptionsObject(options) {
   throw new TypeError(`Options parameter must be an object, not ${options === null ? 'null' : `a ${typeof options}`}`);
 }
 
-function CopyOptions(options) {
-  const optionsCopy = ObjectCreate(null);
-  CopyDataProperties(optionsCopy, GetOptionsObject(options), []);
-  return optionsCopy;
+export function SnapshotOwnProperties(source, proto, excludedKeys = [], excludedValues = []) {
+  const copy = ObjectCreate(proto);
+  CopyDataProperties(copy, ToObject(source), excludedKeys, excludedValues);
+  return copy;
 }
 
 export function GetOption(options, property, allowedValues, fallback) {

polyfill/lib/zoneddatetime.mjs

@@ -444,12 +444,11 @@ export class ZonedDateTime {
     if (!ES.IsTemporalZonedDateTime(this)) throw new TypeError('invalid receiver');
     options = ES.GetOptionsObject(options);
 
-    const optionsCopy = ObjectCreate(null);
     // This is not quite per specification, but this polyfill's DateTimeFormat
     // already doesn't match the InitializeDateTimeFormat operation, and the
     // access order might change anyway;
     // see https://github.com/tc39/ecma402/issues/747
-    ES.CopyDataProperties(optionsCopy, options, ['timeZone']);
+    const optionsCopy = ES.SnapshotOwnProperties(options, null, ['timeZone']);
 
     if (options.timeZone !== undefined) {
       throw new TypeError('ZonedDateTime toLocaleString does not accept a timeZone option');

spec/abstractops.html

@@ -150,27 +150,6 @@ <h1>GetOptionsObject ( _options_ )</h1>
     </emu-alg>
   </emu-clause>
 
-  <emu-clause id="sec-temporal-copyoptions" type="abstract operation">
-    <h1>
-      CopyOptions (
-        _options_: an ECMAScript language value,
-      ): either a normal completion containing an Object, or a throw completion
-    </h1>
-    <dl class="header">
-      <dt>description</dt>
-      <dd>
-        It returns an Object suitable for use with GetOption.
-        Unlike GetOptionsObject, it will never return the same Object as _options_ itself.
-        It always returns a new Object for which the value in its [[Prototype]] internal slot is *null* and every property is a data property.
-      </dd>
-    </dl>
-    <emu-alg>
-      1. Let _optionsCopy_ be OrdinaryObjectCreate(*null*).
-      1. Perform ? CopyDataProperties(_optionsCopy_, ? GetOptionsObject(_options_), &laquo; &raquo;).
-      1. Return _optionsCopy_.
-    </emu-alg>
-  </emu-clause>
-
   <!-- Copied from ECMA-402 GetOption -->
   <emu-clause id="sec-getoption" type="abstract operation">
     <h1>

spec/calendar.html

@@ -1505,12 +1505,8 @@ <h1>Temporal.Calendar.prototype.mergeFields ( _fields_, _additionalFields_ )</h1
       <emu-alg>
         1. Let _calendar_ be the *this* value.
         1. Perform ? RequireInternalSlot(_calendar_, [[InitializedTemporalCalendar]]).
-        1. Set _fields_ to ? ToObject(_fields_).
-        1. Let _fieldsCopy_ be OrdinaryObjectCreate(*null*).
-        1. Perform ? CopyDataProperties(_fieldsCopy_, _fields_, « », « *undefined* »).
-        1. Set _additionalFields_ to ? ToObject(_additionalFields_).
-        1. Let _additionalFieldsCopy_ be OrdinaryObjectCreate(*null*).
-        1. Perform ? CopyDataProperties(_additionalFieldsCopy_, _additionalFields_, « », « *undefined* »).
+        1. Let _fieldsCopy_ be ? SnapshotOwnProperties(_fields_, *null*, « », « *undefined* »).
+        1. Let _additionalFieldsCopy_ be ? SnapshotOwnProperties(_additionalFields_, *null*, « », « *undefined* »).
         1. NOTE: Every property of _fieldsCopy_ and _additionalFieldsCopy_ is an enumerable data property with a non-*undefined* value, but some property keys may be Symbols.
         1. Let _additionalKeys_ be ! _additionalFieldsCopy_.[[OwnPropertyKeys]]().
         1. Assert: _calendar_.[[Identifier]] is *"iso8601"*.

spec/instant.html

@@ -678,7 +678,7 @@ <h1>
       <emu-alg>
         1. If _operation_ is ~since~, let _sign_ be -1. Otherwise, let _sign_ be 1.
         1. Set _other_ to ? ToTemporalInstant(_other_).
-        1. Let _resolvedOptions_ be ? CopyOptions(_options_).
+        1. Let _resolvedOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _settings_ be ? GetDifferenceSettings(_operation_, _resolvedOptions_, ~time~, &laquo; &raquo;, *"nanosecond"*, *"second"*).
         1. Let _result_ be DifferenceInstant(_instant_.[[Nanoseconds]], _other_.[[Nanoseconds]], _settings_.[[RoundingIncrement]], _settings_.[[SmallestUnit]], _settings_.[[LargestUnit]], _settings_.[[RoundingMode]]).
         1. Return ! CreateTemporalDuration(0, 0, 0, 0, _sign_ &times; _result_.[[Hours]], _sign_ &times; _result_.[[Minutes]], _sign_ &times; _result_.[[Seconds]], _sign_ &times; _result_.[[Milliseconds]], _sign_ &times; _result_.[[Microseconds]], _sign_ &times; _result_.[[Nanoseconds]]).

spec/intl.html

@@ -2227,12 +2227,8 @@ <h1>Temporal.Calendar.prototype.mergeFields ( _fields_, _additionalFields_ )</h1
           <emu-alg>
             1. Let _calendar_ be the *this* value.
             1. Perform ? RequireInternalSlot(_calendar_, [[InitializedTemporalCalendar]]).
-            1. Set _fields_ to ? ToObject(_fields_).
-            1. Let _fieldsCopy_ be OrdinaryObjectCreate(*null*).
-            1. Perform ? CopyDataProperties(_fieldsCopy_, _fields_, « », « *undefined* »).
-            1. Set _additionalFields_ to ? ToObject(_additionalFields_).
-            1. Let _additionalFieldsCopy_ be OrdinaryObjectCreate(*null*).
-            1. Perform ? CopyDataProperties(_additionalFieldsCopy_, _additionalFields_, « », « *undefined* »).
+            1. Let _fieldsCopy_ be ? SnapshotOwnProperties(_fields_, *null*, « », « *undefined* »).
+            1. Let _additionalFieldsCopy_ be ? SnapshotOwnProperties(_additionalFields_, *null*, « », « *undefined* »).
             1. NOTE: Every property of _fieldsCopy_ and _additionalFieldsCopy_ is an enumerable data property with non-*undefined* value, but some property keys may be Symbols.
             1. Let _additionalKeys_ be ! _additionalFieldsCopy_.[[OwnPropertyKeys]]().
             1. If _calendar_.[[Identifier]] is *"iso8601"*, then

spec/mainadditions.html

@@ -186,6 +186,32 @@ <h1>
     </emu-note>
   </emu-clause>
 
+  <ins class="block">
+    <emu-clause id="sec-snapshotownproperties" type="abstract operation">
+      <h1>
+        SnapshotOwnProperties (
+          _source_: an ECMAScript language value,
+          _proto_: an Object or *null*,
+          optional _excludedKeys_: a List of property keys,
+          optional _excludedValues_: a List of ECMAScript language values,
+        ): either a normal completion containing an Object, or a throw completion
+      </h1>
+      <dl class="header">
+        <dt>description</dt>
+        <dd>
+          It enumerates the own properties of _source_ and copies them into data properties on a new object with the specified prototype, subject to the specified exclusions.
+        </dd>
+      </dl>
+      <emu-alg>
+        1. Let _copy_ be OrdinaryObjectCreate(_proto_).
+        1. If _excludedKeys_ is not present, set _excludedKeys_ to « ».
+        1. If _excludedValues_ is not present, set _excludedValues_ to « ».
+        1. Perform ? CopyDataProperties(_copy_, ? ToObject(_source_), _excludedKeys_, _excludedValues_).
+        1. Return _copy_.
+      </emu-alg>
+    </emu-clause>
+  </ins>
+
   <emu-clause id="sec-temporal-date-constructor">
     <h1><a href="https://tc39.es/ecma262/#sec-date-constructor">The Date Constructor</a></h1>
     <emu-clause id="sec-temporal-date">

spec/plaindate.html

@@ -978,7 +978,7 @@ <h1>
         1. If _operation_ is ~since~, let _sign_ be -1. Otherwise, let _sign_ be 1.
         1. Set _other_ to ? ToTemporalDate(_other_).
         1. If ? CalendarEquals(_temporalDate_.[[Calendar]], _other_.[[Calendar]]) is *false*, throw a *RangeError* exception.
-        1. Let _resolvedOptions_ be ? CopyOptions(_options_).
+        1. Let _resolvedOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _settings_ be ? GetDifferenceSettings(_operation_, _resolvedOptions_, ~date~, &laquo; &raquo;, *"day"*, *"day"*).
         1. Perform ! CreateDataPropertyOrThrow(_resolvedOptions_, *"largestUnit"*, _settings_.[[LargestUnit]]).
         1. Let _result_ be ? CalendarDateUntil(_temporalDate_.[[Calendar]], _temporalDate_, _other_, _resolvedOptions_).

spec/plaindatetime.html

@@ -1139,7 +1139,7 @@ <h1>
         1. Let _date1_ be ! CreateTemporalDate(_adjustedDate_.[[Year]], _adjustedDate_.[[Month]], _adjustedDate_.[[Day]], _calendar_).
         1. Let _date2_ be ! CreateTemporalDate(_y2_, _mon2_, _d2_, _calendar_).
         1. Let _dateLargestUnit_ be ! LargerOfTwoTemporalUnits(*"day"*, _largestUnit_).
-        1. Let _untilOptions_ be ? CopyOptions(_options_).
+        1. Let _untilOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Perform ! CreateDataPropertyOrThrow(_untilOptions_, *"largestUnit"*, _dateLargestUnit_).
         1. Let _dateDifference_ be ? CalendarDateUntil(_calendar_, _date1_, _date2_, _untilOptions_).
         1. Let _balanceResult_ be ? <emu-meta suppress-effects="user-code">BalanceDuration(_dateDifference_.[[Days]], _timeDifference_.[[Hours]], _timeDifference_.[[Minutes]], _timeDifference_.[[Seconds]], _timeDifference_.[[Milliseconds]], _timeDifference_.[[Microseconds]], _timeDifference_.[[Nanoseconds]], _largestUnit_)</emu-meta>.
@@ -1163,7 +1163,7 @@ <h1>
         1. If _operation_ is ~since~, let _sign_ be -1. Otherwise, let _sign_ be 1.
         1. Set _other_ to ? ToTemporalDateTime(_other_).
         1. If ? CalendarEquals(_dateTime_.[[Calendar]], _other_.[[Calendar]]) is *false*, throw a *RangeError* exception.
-        1. Let _resolvedOptions_ be ? CopyOptions(_options_).
+        1. Let _resolvedOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _settings_ be ? GetDifferenceSettings(_operation_, _resolvedOptions_, ~datetime~, &laquo; &raquo;, *"nanosecond"*, *"day"*).
         1. Let _diff_ be ? DifferenceISODateTime(_dateTime_.[[ISOYear]], _dateTime_.[[ISOMonth]], _dateTime_.[[ISODay]], _dateTime_.[[ISOHour]], _dateTime_.[[ISOMinute]], _dateTime_.[[ISOSecond]], _dateTime_.[[ISOMillisecond]], _dateTime_.[[ISOMicrosecond]], _dateTime_.[[ISONanosecond]], _other_.[[ISOYear]], _other_.[[ISOMonth]], _other_.[[ISODay]], _other_.[[ISOHour]], _other_.[[ISOMinute]], _other_.[[ISOSecond]], _other_.[[ISOMillisecond]], _other_.[[ISOMicrosecond]], _other_.[[ISONanosecond]], _dateTime_.[[Calendar]], _settings_.[[LargestUnit]], _resolvedOptions_).
         1. Let _relativeTo_ be ! CreateTemporalDate(_dateTime_.[[ISOYear]], _dateTime_.[[ISOMonth]], _dateTime_.[[ISODay]], _dateTime_.[[Calendar]]).

spec/plaintime.html

@@ -921,7 +921,7 @@ <h1>
       <emu-alg>
         1. If _operation_ is ~since~, let _sign_ be -1. Otherwise, let _sign_ be 1.
         1. Set _other_ to ? ToTemporalTime(_other_).
-        1. Let _resolvedOptions_ be ? CopyOptions(_options_).
+        1. Let _resolvedOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _settings_ be ? GetDifferenceSettings(_operation_, _resolvedOptions_, ~time~, &laquo; &raquo;, *"nanosecond"*, *"hour"*).
         1. Let _result_ be ! DifferenceTime(_temporalTime_.[[ISOHour]], _temporalTime_.[[ISOMinute]], _temporalTime_.[[ISOSecond]], _temporalTime_.[[ISOMillisecond]], _temporalTime_.[[ISOMicrosecond]], _temporalTime_.[[ISONanosecond]], _other_.[[ISOHour]], _other_.[[ISOMinute]], _other_.[[ISOSecond]], _other_.[[ISOMillisecond]], _other_.[[ISOMicrosecond]], _other_.[[ISONanosecond]]).
         1. Set _result_ to (! RoundDuration(0, 0, 0, 0, _result_.[[Hours]], _result_.[[Minutes]], _result_.[[Seconds]], _result_.[[Milliseconds]], _result_.[[Microseconds]], _result_.[[Nanoseconds]], _settings_.[[RoundingIncrement]], _settings_.[[SmallestUnit]], _settings_.[[RoundingMode]])).[[DurationRecord]].

spec/plainyearmonth.html

@@ -628,7 +628,7 @@ <h1>
         1. Set _other_ to ? ToTemporalYearMonth(_other_).
         1. Let _calendar_ be _yearMonth_.[[Calendar]].
         1. If ? CalendarEquals(_calendar_, _other_.[[Calendar]]) is *false*, throw a *RangeError* exception.
-        1. Let _resolvedOptions_ be ? CopyOptions(_options_).
+        1. Let _resolvedOptions_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _settings_ be ? GetDifferenceSettings(_operation_, _resolvedOptions_, ~date~, &laquo; *"week"*, *"day"* &raquo;, *"month"*, *"year"*).
         1. Perform ! CreateDataPropertyOrThrow(_resolvedOptions_, *"largestUnit"*, _settings_.[[LargestUnit]]).
         1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"monthCode"*, *"year"* »).
@@ -666,8 +666,7 @@ <h1>
         1. Let _calendar_ be _yearMonth_.[[Calendar]].
         1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"monthCode"*, *"year"* »).
         1. Let _fields_ be ? PrepareTemporalFields(_yearMonth_, _fieldNames_, «»).
-        1. Let _fieldsCopy_ be OrdinaryObjectCreate(*null*).
-        1. Perform ! CopyDataProperties(_fieldsCopy_, _fields_, «»).
+        1. Let _fieldsCopy_ be ! SnapshotOwnProperties(_fields_, *null*).
         1. Perform ! CreateDataPropertyOrThrow(_fields_, *"day"*, *1*<sub>𝔽</sub>).
         1. Let _intermediateDate_ be ? CalendarDateFromFields(_calendar_, _fields_).
         1. Let _sign_ be ! DurationSign(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
@@ -683,7 +682,7 @@ <h1>
         1. Else,
           1. Let _date_ be _intermediateDate_.
         1. Let _durationToAdd_ be ! CreateTemporalDuration(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
-        1. Let _optionsCopy_ be ? CopyOptions(_options_).
+        1. Let _optionsCopy_ be ? SnapshotOwnProperties(? GetOptionsObject(_options_), *null*).
         1. Let _addedDate_ be ? CalendarDateAdd(_calendar_, _date_, _durationToAdd_, _options_, _dateAdd_).
         1. Let _addedDateFields_ be ? PrepareTemporalFields(_addedDate_, _fieldNames_, «»).
         1. Return ? CalendarYearMonthFromFields(_calendar_, _addedDateFields_, _optionsCopy_).