Fast-path conversion of a Temporal object to Temporal.Calendar

If passing a Temporal object with a [[Calendar]] internal slot where a calendar is expected, then read that slot instead of doing a Get on the "calendar" property. (The Get operation was also not consistently done throughout the existing spec text, so fix that as well. This means the CalendarFrom operation becomes redundant, so remove it.) See: #1428
tc39 · Apr 13, 2021 · ba1b1fa · ba1b1fa
1 parent 7badec0
commit ba1b1fa
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Showing 3 changed files with 24 additions and 38 deletions.
diff --git a/polyfill/lib/calendar.mjs b/polyfill/lib/calendar.mjs
@@ -163,7 +163,7 @@ export class Calendar {
     return ES.ToString(this);
   }
   static from(item) {
-    return ES.CalendarFrom(item);
+    return ES.ToTemporalCalendar(item);
   }
 }
 

diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
@@ -1501,24 +1501,6 @@ export const ES = ObjectAssign({}, ES2020, {
     const TemporalCalendar = GetIntrinsic('%Temporal.Calendar%');
     return new TemporalCalendar('iso8601');
   },
-  CalendarFrom: (item) => {
-    if (ES.Type(item) === 'Object') {
-      if (!('calendar' in item)) return item;
-      item = item.calendar;
-      if (ES.Type(item) === 'Object' && !('calendar' in item)) return item;
-    }
-    const stringIdent = ES.ToString(item);
-    const TemporalCalendar = GetIntrinsic('%Temporal.Calendar%');
-    if (IsBuiltinCalendar(stringIdent)) return new TemporalCalendar(stringIdent);
-    let calendar;
-    try {
-      ({ calendar } = ES.ParseISODateTime(stringIdent, { zoneRequired: false }));
-    } catch {
-      throw new RangeError(`Invalid calendar: ${stringIdent}`);
-    }
-    if (!calendar) calendar = 'iso8601';
-    return new TemporalCalendar(calendar);
-  },
   CalendarFields: (calendar, fieldNames) => {
     const fields = ES.GetMethod(calendar, 'fields');
     if (fields !== undefined) fieldNames = ES.Call(fields, calendar, [fieldNames]);
@@ -1624,10 +1606,22 @@ export const ES = ObjectAssign({}, ES2020, {
 
   ToTemporalCalendar: (calendarLike) => {
     if (ES.Type(calendarLike) === 'Object') {
-      return calendarLike;
+      if (HasSlot(calendarLike, CALENDAR)) return GetSlot(calendarLike, CALENDAR);
+      if (!('calendar' in calendarLike)) return calendarLike;
+      calendarLike = calendarLike.calendar;
+      if (ES.Type(calendarLike) === 'Object' && !('calendar' in calendarLike)) return calendarLike;
     }
     const identifier = ES.ToString(calendarLike);
-    return ES.CalendarFrom(identifier);
+    const TemporalCalendar = GetIntrinsic('%Temporal.Calendar%');
+    if (IsBuiltinCalendar(identifier)) return new TemporalCalendar(identifier);
+    let calendar;
+    try {
+      ({ calendar } = ES.ParseISODateTime(identifier, { zoneRequired: false }));
+    } catch {
+      throw new RangeError(`Invalid calendar: ${identifier}`);
+    }
+    if (!calendar) calendar = 'iso8601';
+    return new TemporalCalendar(calendar);
   },
   CalendarCompare: (one, two) => {
     const cal1 = ES.ToString(one);

diff --git a/spec/calendar.html b/spec/calendar.html
@@ -237,9 +237,15 @@ <h1>CalendarInLeapYear ( _calendar_, _dateLike_ )</h1>
       <h1>ToTemporalCalendar ( _temporalCalendarLike_ )</h1>
       <emu-alg>
         1. If Type(_temporalCalendarLike_) is Object, then
-          1. Return _temporalCalendarLike_.
+          1. If _temporalCalendarLike_ has an [[InitializedTemporalDate]], [[InitializedTemporalDateTime]], [[InitializedTemporalMonthDay]], [[InitializedTemporalTime]], [[InitializedTemporalYearMonth]], or [[InitializedTemporalZonedDateTime]] internal slot, then
+            1. Return _temporalCalendarLike_.[[Calendar]].
+          1. If ? HasProperty(_item_, *"calendar"*) is *false*, return _item_.
+          1. Set _item_ to ? Get(_item_, *"calendar"*).
+          1. If Type(_item_) is Object and ? HasProperty(_item_, *"calendar"*) is *false*, return _item_.
         1. Let _identifier_ be ? ToString(_temporalCalendarLike_).
-        1. Return ? CalendarFrom(_identifier_, %Temporal.Calendar%).
+        1. If ! IsBuiltinCalendar(_identifier_) is *false*, then
+          1. Let _identifier_ be ? ParseTemporalCalendarString(_identifier_).
+        1. Return ? CreateTemporalCalendar(_identifier_).
       </emu-alg>
     </emu-clause>
 
@@ -268,20 +274,6 @@ <h1>GetOptionalTemporalCalendar ( _item_ )</h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-temporal-calendarfrom" aoid="CalendarFrom">
-      <h1>CalendarFrom ( _identifier_ )</h1>
-      <emu-alg>
-        1. If Type(_item_) is Object, then
-          1. If ? HasProperty(_item_, *"calendar"*) is *false*, return _item_.
-          1. Set _item_ to ? Get(_item_, *"calendar"*).
-          1. If Type(_item_) is Object and ? HasProperty(_item_, *"calendar"*) is *false*, return _item_.
-        1. Let _string_ be ? ToString(_item_).
-        1. If ! IsBuiltinCalendar(_string_) is *false*, then
-          1. Let _string_ be ? ParseTemporalCalendarString(_string_).
-        1. Return ? CreateTemporalCalendar(_string_).
-      </emu-alg>
-    </emu-clause>
-
     <emu-clause id="sec-temporal-datefromfields" aoid="DateFromFields">
       <h1>DateFromFields ( _calendar_, _fields_, _options_ )</h1>
       <emu-alg>
@@ -656,7 +648,7 @@ <h1>Temporal.Calendar.from ( _item_ )</h1>
         The following steps are taken:
       </p>
       <emu-alg>
-        1. Return ? CalendarFrom(_item_).
+        1. Return ? ToTemporalCalendar(_item_).
       </emu-alg>
     </emu-clause>
   </emu-clause>