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remapping-era.js (4616B)

      1 // |reftest| skip-if(!this.hasOwnProperty('Temporal')) -- Temporal is not enabled unconditionally
      2 // Copyright (C) 2025 Igalia, S.L. All rights reserved.
      3 // This code is governed by the BSD license found in the LICENSE file.
      4 
      5 /*---
      6 esid: sec-temporal.plainyearmonth.from
      7 description: Test remapping behaviour of regnal eras
      8 info: |
      9  CalendarYearMonthFromFields:
     10  1. Perform ? CalendarResolveFields(_calendar_, _fields_, ~year-month~).
     11  2. Let _firstDayIndex_ be the 1-based index of the first day of the month
     12     described by _fields_ (i.e., 1 unless the month's first day is skipped by
     13     this calendar.)
     14  3. Set _fields_.[[Day]] to _firstDayIndex_.
     15  4. Let result be ? CalendarDateToISO(_calendar_, _fields_, _overflow_).
     16 
     17  CalendarResolveFields:
     18  When the fields of _fields_ are inconsistent with respect to a non-unset
     19  _fields_.[[Era]], it is recommended that _fields_.[[Era]] and
     20  _fields_.[[EraYear]] be updated to resolve the inconsistency by lenient
     21  interpretation of out-of-bounds values (rather than throwing a *RangeError*),
     22  which is particularly useful for consistent interpretation of dates in
     23  calendars with regnal eras.
     24 
     25 includes: [temporalHelpers.js]
     26 features: [Temporal, Intl.Era-monthcode]
     27 ---*/
     28 
     29 // Based on a test originally by André Bargull <andre.bargull@gmail.com>
     30 
     31 // Notes:
     32 // - "heisei" era started January 8, 1989.
     33 // - "reiwa" era started May 1, 2019.
     34 
     35 for (const overflow of ["constrain", "reject"]) {
     36  function test(fields) {
     37    return Temporal.PlainYearMonth.from({ ...fields, calendar: "japanese" }, { overflow });
     38  }
     39 
     40  // Reiwa era started in month 5 of the year, so the era of month 1 is remapped
     41  // to be the correct one for the month.
     42  TemporalHelpers.assertPlainYearMonth(
     43    test({ era: "reiwa", eraYear: 1, monthCode: "M01" }),
     44    2019, 1, "M01",
     45    "Reiwa 1 before May is mapped to Heisei 31",
     46    "heisei", 31, /* reference day = */ 1
     47  );
     48 
     49  // Reiwa era started on the first day of the month, so the reference day 1
     50  // does not need remapping.
     51  TemporalHelpers.assertPlainYearMonth(
     52    test({ era: "reiwa", eraYear: 1, monthCode: "M05" }),
     53    2019, 5, "M05",
     54    "reference day is 1",
     55    "reiwa", 1, /* reference day = */ 1
     56  );
     57 
     58  // Heisei era started on the eighth day of the month, but PlainYearMonth
     59  // references the first day of the month. So the era is remapped to be the
     60  // correct one for the reference day.
     61  TemporalHelpers.assertPlainYearMonth(
     62    test({ era: "heisei", eraYear: 1, monthCode: "M01" }),
     63    1989, 1, "M01",
     64    "01-01 Heisei 1 is remapped to 01-01 Showa 64",
     65    "showa", 64, /* reference day = */ 1
     66  );
     67 
     68  // Era year past the end of the Heisei era is remapped to Reiwa era
     69  TemporalHelpers.assertPlainYearMonth(
     70    test({ era: "heisei", eraYear: 37, monthCode: "M04" }),
     71    2025, 4, "M04",
     72    "Heisei 37 is remapped to Reiwa 7",
     73    "reiwa", 7, /* reference day = */ 1
     74  );
     75 
     76  // Zero year in a 1-based era is remapped to the previous era
     77  TemporalHelpers.assertPlainYearMonth(
     78    test({ era: "reiwa", eraYear: 0, monthCode: "M04" }),
     79    2018, 4, "M04",
     80    "Reiwa 0 is remapped to Heisei 30",
     81    "heisei", 30, /* reference day = */ 1
     82  );
     83 
     84  // Negative year in a forwards-counting era is remapped to the previous era
     85  TemporalHelpers.assertPlainYearMonth(
     86    test({ era: "reiwa", eraYear: -20, monthCode: "M04" }),
     87    1998, 4, "M04",
     88    "Reiwa -20 is remapped to Heisei 10",
     89    "heisei", 10, /* reference day = */ 1
     90  );
     91 
     92  // Test the last two things for Gregorian eras as well
     93  function testGregorian(fields) {
     94    return Temporal.PlainYearMonth.from({ ...fields, calendar: "gregory" }, { overflow });
     95  }
     96  TemporalHelpers.assertPlainYearMonth(
     97    testGregorian({ era: "ce", eraYear: 0, monthCode: "M04" }),
     98    0, 4, "M04",
     99    "0 CE is remapped to 1 BCE",
    100    "bce", 1, /* reference day = */ 1
    101  );
    102  TemporalHelpers.assertPlainYearMonth(
    103    testGregorian({ era: "ce", eraYear: -20, monthCode: "M04" }),
    104    -20, 4, "M04",
    105    "-20 CE is remapped to 21 BCE",
    106    "bce", 21, /* reference day = */ 1
    107  );
    108 
    109  // Zero year in a backwards-counting era is remapped to the next era
    110  TemporalHelpers.assertPlainYearMonth(
    111    testGregorian({ era: "bce", eraYear: 0, monthCode: "M04" }),
    112    1, 4, "M04",
    113    "0 BCE is remapped to 1 CE",
    114    "ce", 1, /* reference day = */ 1
    115  );
    116 
    117  // Negative year in a backwards-counting era is remapped to the next era
    118  TemporalHelpers.assertPlainYearMonth(
    119    testGregorian({ era: "bce", eraYear: -20, monthCode: "M04" }),
    120    21, 4, "M04",
    121    "-20 BCE is remapped to 21 CE",
    122    "ce", 21, /* reference day = */ 1
    123  );
    124 }
    125 
    126 reportCompare(0, 0);