Temporal: Add coverage for weird PlainMonthDay leap day constrain case

If you have a leap day, such as February 29, and you get input such as
{ monthCode: "M02", day: 30 }, { overflow: "constrain" }, then you want
the day to be constrained to the leap day February 29, not February 28
as the maximum day would be in a common year. Add tests for this case
for each supported calendar.
This commit is contained in:
Philip Chimento 2025-04-17 17:24:20 -07:00 committed by Philip Chimento
parent fa0a3081bd
commit c3c318cf11
2 changed files with 43 additions and 0 deletions

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// 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.plainmonthday.from
description: Properly constrain February 30 to February 29, not 28
features: [Temporal]
---*/
const md = Temporal.PlainMonthDay.from({ monthCode: "M02", day: 30 }, { overflow: "constrain" });
assert.sameValue(md.day, 29, "M02-30 should constrain to 29, not 28");

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// 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.plainmonthday.from
description: Properly constrain a day that is one past a leap day
features: [Temporal]
---*/
const tests = [
["buddhist", "M02", 30],
["chinese", "M01", 31],
["coptic", "M13", 7],
["dangi", "M01", 31],
["ethioaa", "M13", 7],
["ethiopic", "M13", 7],
["gregory", "M02", 30],
["hebrew", "M02", 31],
["indian", "M01", 32],
["islamic-civil", "M01", 31],
["islamic-tbla", "M01", 31],
["islamic-umalqura", "M01", 31],
["japanese", "M02", 30],
["persian", "M12", 31],
["roc", "M02", 30],
];
for (const [calendar, monthCode, day] of tests) {
const md = Temporal.PlainMonthDay.from({ calendar, monthCode, day }, { overflow: "constrain" });
assert.sameValue(md.day, day - 1,
`${calendar}: ${monthCode}-${day} should constrain to ${day - 1}, not ${day - 2}`)
}