Temporal: Tests for correct intermediate value in ZonedDateTime diffe…

…rence/rounding

These test cases ensure that DST disambiguation does not take place on
intermediate values that are not the start or the end of the calculation.

Note that NormalizedTimeDurationToDays is no longer called inside
Temporal.Duration.prototype.add/subtract, so a few tests can be deleted.

Other tests need to be adjusted because NormalizedTimeDurationToDays is
no longer called inside Temporal.ZonedDateTime.prototype.since/until via
DifferenceZonedDateTime, although it is still called as part of rounding.

In addition, new tests for the now-fixed edge case are added.

See tc39/proposal-temporal#2760

test/built-ins/Temporal/Duration/prototype/add/order-of-operations.js

@@ -343,13 +343,6 @@ const expectedOpsForZonedRelativeTo = expected.concat([
   // AddDuration → DifferenceZonedDateTime → AddZonedDateTime
   "call options.relativeTo.calendar.dateAdd",
   "call options.relativeTo.timeZone.getPossibleInstantsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays
-  "call options.relativeTo.timeZone.getOffsetNanosecondsFor",
-  "call options.relativeTo.timeZone.getOffsetNanosecondsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays → AddZonedDateTime 1
-  "call options.relativeTo.timeZone.getPossibleInstantsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays → AddZonedDateTime 2
-  "call options.relativeTo.timeZone.getPossibleInstantsFor",
 ]);
 
 const zonedRelativeTo = TemporalHelpers.propertyBagObserver(actual, {

test/built-ins/Temporal/Duration/prototype/round/dst-rounding-result.js

@@ -0,0 +1,45 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+    Rounding the resulting duration takes the time zone's UTC offset shifts
+    into account
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = TemporalHelpers.springForwardFallBackTimeZone();
+
+// Based on a test case by Adam Shaw
+
+{
+  // Date part of duration lands on skipped DST hour, causing disambiguation
+  const duration = new Temporal.Duration(0, 1, 0, 15, 12);
+  const relativeTo = new Temporal.ZonedDateTime(
+    950868000_000_000_000n /* = 2000-02-18T10Z */,
+    timeZone); /* = 2000-02-18T02-08 in local time */
+
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", relativeTo }),
+    0, 2, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days 12 hours should be exactly 1.5 months, which rounds up to 2 months");
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", roundingMode: 'halfTrunc', relativeTo }),
+    0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days 12 hours should be exactly 1.5 months, which rounds down to 1 month");
+}
+
+{
+  // Month-only part of duration lands on skipped DST hour, should not cause
+  // disambiguation
+  const duration = new Temporal.Duration(0, 1, 0, 15);
+  const relativeTo = new Temporal.ZonedDateTime(
+    951991200_000_000_000n /* = 2000-03-02T10Z */,
+    timeZone); /* = 2000-03-02T02-08 in local time */
+
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", relativeTo }),
+    0, 2, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days should be exactly 1.5 months, which rounds up to 2 months");
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", roundingMode: 'halfTrunc', relativeTo }),
+    0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days should be exactly 1.5 months, which rounds down to 1 month");
+}

test/built-ins/Temporal/Duration/prototype/subtract/order-of-operations.js

@@ -343,13 +343,6 @@ const expectedOpsForZonedRelativeTo = expected.concat([
   // AddDuration → DifferenceZonedDateTime → AddZonedDateTime
   "call options.relativeTo.calendar.dateAdd",
   "call options.relativeTo.timeZone.getPossibleInstantsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays
-  "call options.relativeTo.timeZone.getOffsetNanosecondsFor",
-  "call options.relativeTo.timeZone.getOffsetNanosecondsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays → AddZonedDateTime 1
-  "call options.relativeTo.timeZone.getPossibleInstantsFor",
-  // AddDuration → DifferenceZonedDateTime → NanosecondsToDays → AddZonedDateTime 2
-  "call options.relativeTo.timeZone.getPossibleInstantsFor",
 ]);
 
 const zonedRelativeTo = TemporalHelpers.propertyBagObserver(actual, {