Remove era from main spec

This removes era from Temporal proper, and defines it only the first time a calendar that uses it is constructed. This is in line with era and other custom calendar properties being the domain of ECMA-402. Closes: #1046
tc39 · Oct 26, 2020 · cb036ae · cb036ae
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Showing 11 changed files with 15 additions and 84 deletions.
diff --git a/docs/date.md b/docs/date.md
@@ -168,11 +168,6 @@ date.day;   // => 24
 
 The `calendar` read-only property gives the calendar that the `year`, `month`, and `day` properties are interpreted in.
 
-### date.**era** : unknown
-
-The `era` read-only property is `undefined` when using the ISO 8601 calendar.
-It's used for calendar systems that specify an era in addition to the year.
-
 ### date.**dayOfWeek** : number
 
 The `dayOfWeek` read-only property gives the weekday number that the date falls on.

diff --git a/docs/datetime.md b/docs/datetime.md
@@ -230,11 +230,6 @@ dt.nanosecond;  // => 500
 
 The `calendar` read-only property gives the calendar that the `year`, `month`, and `day` properties are interpreted in.
 
-### datetime.**era** : unknown
-
-The `era` read-only property is `undefined` when using the ISO 8601 calendar.
-It's used for calendar systems that specify an era in addition to the year.
-
 ### datetime.**dayOfWeek** : number
 
 The `dayOfWeek` read-only property gives the weekday number that the date falls on.

diff --git a/docs/yearmonth.md b/docs/yearmonth.md
@@ -159,11 +159,6 @@ ym.month; // => 6
 
 The `calendar` read-only property gives the calendar that the `year` and `month` properties are interpreted in.
 
-### yearmonth.**era** : unknown
-
-The `era` read-only property is `undefined` when using the ISO 8601 calendar.
-It's used for calendar systems that specify an era in addition to the year.
-
 ### yearMonth.**daysInMonth** : number
 
 The `daysInMonth` read-only property gives the number of days in the month.

diff --git a/polyfill/lib/calendar.mjs b/polyfill/lib/calendar.mjs
@@ -80,10 +80,6 @@ export class Calendar {
     void date;
     throw new Error('not implemented');
   }
-  era(date) {
-    void date;
-    throw new Error('not implemented');
-  }
   dayOfWeek(date) {
     void date;
     throw new Error('not implemented');
@@ -243,10 +239,6 @@ class ISO8601Calendar extends Calendar {
     if (!ES.IsTemporalCalendar(this)) throw new TypeError('invalid receiver');
     return GetSlot(date, ISO_DAY);
   }
-  era(date) {
-    void date;
-    return undefined;
-  }
   dayOfWeek(date) {
     if (!ES.IsTemporalCalendar(this)) throw new TypeError('invalid receiver');
     return ES.DayOfWeek(GetSlot(date, ISO_YEAR), GetSlot(date, ISO_MONTH), GetSlot(date, ISO_DAY));
@@ -287,6 +279,15 @@ MakeIntrinsicClass(ISO8601Calendar, 'Temporal.ISO8601Calendar');
 // proposal for ECMA-262. These calendars will be standardized as part of
 // ECMA-402.
 
+function addCustomPropertyGetter(type, name) {
+  Object.defineProperty(GetIntrinsic(`%Temporal.${type}.prototype%`), name, {
+    get() {
+      return this.calendar[name](this);
+    },
+    configurable: true
+  });
+}
+
 // Implementation details for Gregorian calendar
 const gre = {
   isoYear(year, era) {
@@ -300,6 +301,9 @@ const gre = {
 class Gregorian extends ISO8601Calendar {
   constructor() {
     super('gregory');
+    addCustomPropertyGetter('Date', 'era');
+    addCustomPropertyGetter('DateTime', 'era');
+    addCustomPropertyGetter('YearMonth', 'era');
   }
 
   era(date) {
@@ -395,6 +399,9 @@ const jpn = {
 class Japanese extends ISO8601Calendar {
   constructor() {
     super('japanese');
+    addCustomPropertyGetter('Date', 'era');
+    addCustomPropertyGetter('DateTime', 'era');
+    addCustomPropertyGetter('YearMonth', 'era');
   }
 
   era(date) {

diff --git a/polyfill/lib/date.mjs b/polyfill/lib/date.mjs
@@ -60,10 +60,6 @@ export class Date {
     if (!ES.IsTemporalDate(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, CALENDAR);
   }
-  get era() {
-    if (!ES.IsTemporalDate(this)) throw new TypeError('invalid receiver');
-    return GetSlot(this, CALENDAR).era(this);
-  }
   get year() {
     if (!ES.IsTemporalDate(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, CALENDAR).year(this);

diff --git a/polyfill/lib/datetime.mjs b/polyfill/lib/datetime.mjs
@@ -150,10 +150,6 @@ export class DateTime {
     if (!ES.IsTemporalDateTime(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, NANOSECOND);
   }
-  get era() {
-    if (!ES.IsTemporalDateTime(this)) throw new TypeError('invalid receiver');
-    return GetSlot(this, CALENDAR).era(this);
-  }
   get dayOfWeek() {
     if (!ES.IsTemporalDateTime(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, CALENDAR).dayOfWeek(this);

diff --git a/polyfill/lib/yearmonth.mjs b/polyfill/lib/yearmonth.mjs
@@ -56,10 +56,6 @@ export class YearMonth {
     if (!ES.IsTemporalYearMonth(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, CALENDAR);
   }
-  get era() {
-    if (!ES.IsTemporalYearMonth(this)) throw new TypeError('invalid receiver');
-    return GetSlot(this, CALENDAR).era(this);
-  }
   get daysInMonth() {
     if (!ES.IsTemporalYearMonth(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, CALENDAR).daysInMonth(this);

diff --git a/polyfill/test/Calendar/prototype/era/length.js b/polyfill/test/Calendar/prototype/era/length.js
diff --git a/polyfill/test/calendar.mjs b/polyfill/test/calendar.mjs
@@ -55,9 +55,6 @@ describe('Calendar', () => {
       it('Calendar.prototype.day is a Function', () => {
         equal(typeof Calendar.prototype.day, 'function');
       });
-      it('Calendar.prototype.era is a Function', () => {
-        equal(typeof Calendar.prototype.era, 'function');
-      });
       it('Calendar.prototype.dayOfWeek is a Function', () => {
         equal(typeof Calendar.prototype.dayOfWeek, 'function');
       });

diff --git a/spec/calendar.html b/spec/calendar.html
@@ -336,17 +336,6 @@ <h1>Temporal.Calendar.prototype.day ( _date_ )</h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-temporal.calendar.prototype.era">
-      <h1>Temporal.Calendar.prototype.era ( _date_ )</h1>
-      <p>
-        The `era` method takes one argument _date_.
-        The following steps are taken:
-      </p>
-      <emu-alg>
-        1. Throw an *Error* exception.
-      </emu-alg>
-    </emu-clause>
-
     <emu-clause id="sec-temporal.calendar.prototype.dayofweek">
       <h1>Temporal.Calendar.prototype.dayOfWeek ( _date_ )</h1>
       <p>

diff --git a/spec/isocalendar.html b/spec/isocalendar.html
@@ -187,18 +187,6 @@ <h1>Temporal.ISO8601Calendar.prototype.day ( _dateOrDateTime_ )</h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-temporal.iso8601calendar.prototype.era">
-      <h1>Temporal.ISO8601Calendar.prototype.era ( _dateOrDateTime_ )</h1>
-      <p>
-        The `era` method takes one argument _dateOrDateTime_.
-        The following steps are taken:
-      </p>
-      <emu-alg>
-        1. Perform ? RequireOneOfInternalSlots(_dateOrDateTime_, « [[InitializedTemporalDate]], [[InitializedTemporalDateTime]] »).
-        1. Return *undefined*.
-      </emu-alg>
-    </emu-clause>
-
     <emu-clause id="sec-temporal.iso8601calendar.prototype.dayofweek">
       <h1>Temporal.ISO8601Calendar.prototype.dayOfWeek ( _dateOrDateTime_ )</h1>
       <p>