Added test to .from() methods for PlainDate, PlainDateTime,

`PlainYearMonth`, and `ZonedDateTime` verifying era aliases for
non-gregorian calendars (in practice, just `"japanese"`).

Author: ben-allen

test/intl402/Temporal/PlainDate/from/canonicalize-era-codes-non-gregorian.js

@@ -0,0 +1,26 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal-calendarsupportsera
+description: Calendar era code is canonicalized (non-Gregorian calendars)
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+
+const calendarEraAliases = [
+  { calendar: "japanese", canonicalizedEra: "ce", alias: "ad" },
+  { calendar: "japanese", canonicalizedEra: "bce", alias: "bc" }
+];
+
+
+for (const calendarEraAlias of calendarEraAliases) {
+  const calendar = Temporal.PlainDate.from({
+    calendar: calendarEraAlias.calendar,
+    era: calendarEraAlias.alias,
+    eraYear: 1,
+    month: 1,
+    day: 1
+  });
+  assert.sameValue(calendar.era, calendarEraAlias.canonicalizedEra, calendar.era + " should canonicalize to " + calendarEraAlias.canonicalizedEra)
+}

test/intl402/Temporal/PlainDateTime/from/canonicalize-era-codes-non-gregorian.js

@@ -0,0 +1,26 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.from
+description: Calendar era code is canonicalized (non-Gregorian calendars)
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+
+const calendarEraAliases = [
+  { calendar: "japanese", canonicalizedEra: "ce", alias: "ad" },
+  { calendar: "japanese", canonicalizedEra: "bce", alias: "bc" }
+];
+
+
+for (const calendarEraAlias of calendarEraAliases) {
+  const calendar = Temporal.PlainDateTime.from({
+    calendar: calendarEraAlias.calendar,
+    era: calendarEraAlias.alias,
+    eraYear: 1,
+    month: 1,
+    day: 1
+  });
+  assert.sameValue(calendar.era, calendarEraAlias.canonicalizedEra, calendar.era + " should canonicalize to " + calendarEraAlias.canonicalizedEra)
+}

test/intl402/Temporal/PlainYearMonth/from/canonicalize-era-codes-non-gregorian.js

@@ -0,0 +1,26 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal-plainyearmonth.from
+description: Calendar era code is canonicalized (non-Gregorian calendars)
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+
+const calendarEraAliases = [
+  { calendar: "japanese", canonicalizedEra: "ce", alias: "ad" },
+  { calendar: "japanese", canonicalizedEra: "bce", alias: "bc" }
+];
+
+
+for (const calendarEraAlias of calendarEraAliases) {
+  const calendar = Temporal.PlainYearMonth.from({
+    calendar: calendarEraAlias.calendar,
+    era: calendarEraAlias.alias,
+    eraYear: 1,
+    month: 1,
+    day: 1
+  });
+  assert.sameValue(calendar.era, calendarEraAlias.canonicalizedEra, calendar.era + " should canonicalize to " + calendarEraAlias.canonicalizedEra)
+}

test/intl402/Temporal/ZonedDateTime/from/canonicalize-era-codes-non-gregorian.js

@@ -0,0 +1,27 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zonedatetime.from
+description: Calendar era code is canonicalized (non-Gregorian calendars)
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+
+const calendarEraAliases = [
+  { calendar: "japanese", canonicalizedEra: "ce", alias: "ad" },
+  { calendar: "japanese", canonicalizedEra: "bce", alias: "bc" }
+];
+
+
+for (const calendarEraAlias of calendarEraAliases) {
+  const calendar = Temporal.ZonedDateTime.from({
+    calendar: calendarEraAlias.calendar,
+    era: calendarEraAlias.alias,
+    eraYear: 1,
+    month: 1,
+    day: 1,
+    timeZone: "UTC"
+  });
+  assert.sameValue(calendar.era, calendarEraAlias.canonicalizedEra, calendar.era + " should canonicalize to " + calendarEraAlias.canonicalizedEra)
+}