Add tests for Temporal.now.plainDateTime (#3037)

* Temporal.now.plainDateTime: import tests from prop

* Add required metadata

* Correct invalid test

Ensure the error is thrown due to the invocation of the provided method.
Add a separate test to verify how the method is invoked.

* Remove duplicated assertions

* Improve coverage

* Rewrite test to focus on Calendar parameter

The observable interactions with the "timeZone" parameter are verified
by another test which is named for that purpose.

* Remove non-standard test

This test's title suggests that it was intended to verify the behavior
when the "calendar" parameter was undefined. The expected behavior in
that case depends on the presence of a builtin calendar named
"undefined." Test262 cannot definitively assert the presence or absence
of such a calendar.

In contrast to the title, the test body actually uses the calendar name
"japanese."  Test262 cannot definitively assert the presence or absence
of such a calendar.

harness/temporalHelpers.js

@@ -0,0 +1,82 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+description: |
+    This defines helper objects and functions for testing Temporal.
+defines: [TemporalHelpers]
+features: [Symbol.species, Symbol.iterator, Temporal]
+---*/
+
+var TemporalHelpers = {
+  /*
+   * Check that any calendar-carrying Temporal object has its [[Calendar]]
+   * internal slot read by ToTemporalCalendar, and does not fetch the calendar
+   * by calling getters.
+   * The custom calendar object is passed in to func() so that it can do its
+   * own additional assertions involving the calendar if necessary. (Sometimes
+   * there is nothing to assert as the calendar isn't stored anywhere that can
+   * be asserted about.)
+   */
+  checkToTemporalCalendarFastPath(func) {
+    class CalendarFastPathCheck extends Temporal.Calendar {
+      constructor() {
+        super("iso8601");
+      }
+
+      toString() {
+        return "fast-path-check";
+      }
+    }
+    const calendar = new CalendarFastPathCheck();
+
+    const plainDate = new Temporal.PlainDate(2000, 5, 2, calendar);
+    const plainDateTime = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321, calendar);
+    const plainMonthDay = new Temporal.PlainMonthDay(5, 2, calendar);
+    const plainYearMonth = new Temporal.PlainYearMonth(2000, 5, calendar);
+    const zonedDateTime = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, "UTC", calendar);
+
+    [plainDate, plainDateTime, plainMonthDay, plainYearMonth, zonedDateTime].forEach((temporalObject) => {
+      const actual = [];
+      const expected = [];
+
+      Object.defineProperty(temporalObject, "calendar", {
+        get() {
+          actual.push("get calendar");
+          return calendar;
+        },
+      });
+
+      func(temporalObject, calendar);
+      assert.compareArray(actual, expected, "calendar getter not called");
+    });
+  },
+
+  /*
+   * specificOffsetTimeZone():
+   *
+   * This returns an instance of a custom time zone class, which returns a
+   * specific custom value from its getOffsetNanosecondsFrom() method. This is
+   * for the purpose of testing the validation of what this method returns.
+   *
+   * It also returns an empty array from getPossibleInstantsFor(), so as to
+   * trigger calls to getOffsetNanosecondsFor() when used from the
+   * BuiltinTimeZoneGetInstantFor operation.
+   */
+  specificOffsetTimeZone(offsetValue) {
+    class SpecificOffsetTimeZone extends Temporal.TimeZone {
+      constructor(offsetValue) {
+        super("UTC");
+        this._offsetValue = offsetValue;
+      }
+
+      getOffsetNanosecondsFor() {
+        return this._offsetValue;
+      }
+
+      getPossibleInstantsFor() {
+        return [];
+      }
+    }
+    return new SpecificOffsetTimeZone(offsetValue);
+  },
+};

test/built-ins/Temporal/now/plainDateTime/calendar-function.js

@@ -0,0 +1,46 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Behavior when provided calendar value is a function
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const actual = [];
+const expected = [
+  "has timeZone.timeZone",
+  "get timeZone.getOffsetNanosecondsFor",
+  "call timeZone.getOffsetNanosecondsFor",
+];
+const calendar = function() {};
+const timeZone = new Proxy({
+  getOffsetNanosecondsFor(instant) {
+    actual.push("call timeZone.getOffsetNanosecondsFor");
+    return -Number(instant.epochNanoseconds % 86400_000_000_000n);
+  },
+}, {
+  has(target, property) {
+    actual.push(`has timeZone.${property}`);
+    return property in target;
+  },
+  get(target, property) {
+    actual.push(`get timeZone.${property}`);
+    return target[property];
+  },
+});
+
+Object.defineProperty(Temporal.Calendar, "from", {
+  get() {
+    actual.push("get Temporal.Calendar.from");
+    return undefined;
+  },
+});
+
+const result = Temporal.now.plainDateTime(calendar, timeZone);
+for (const property of ["hour", "minute", "second", "millisecond", "microsecond", "nanosecond"]) {
+  assert.sameValue(result[property], 0, property);
+}
+
+assert.compareArray(actual, expected);

test/built-ins/Temporal/now/plainDateTime/calendar-object-fail-call-tostring.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by invoking "toString" property
+features: [Temporal]
+---*/
+
+var calendar = {
+  calendar: {
+    calendar: true,
+    toString: function() {
+      throw new Test262Error();
+    },
+  }
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime(calendar);
+});

test/built-ins/Temporal/now/plainDateTime/calendar-object-fail-get-calendar.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by retrieving value of "calendar" property
+features: [Temporal]
+---*/
+
+var calendar = {
+  get calendar() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime(calendar);
+});

test/built-ins/Temporal/now/plainDateTime/calendar-object-fail-has-calendar.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by checking presence of "calendar" property
+features: [Temporal]
+---*/
+
+var calendar = new Proxy({}, {
+  has: function(target, property) {
+    if (property === 'calendar') {
+      throw new Test262Error();
+    }
+  },
+});
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime(calendar);
+});

test/built-ins/Temporal/now/plainDateTime/calendar-object-fail-has-nested-calendar.js

@@ -0,0 +1,21 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by checking presence of nested "calendar" property
+features: [Temporal]
+---*/
+
+var calendar = {
+  calendar: new Proxy({}, {
+    has: function(target, property) {
+      if (property === 'calendar') {
+        throw new Test262Error();
+      }
+    },
+  })
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime(calendar);
+});

test/built-ins/Temporal/now/plainDateTime/calendar-object.js

@@ -0,0 +1,61 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Observable interactions with the provided calendar-like object
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const actual = [];
+const expected = [
+  'has calendar.calendar',
+  'get calendar.calendar',
+  'has nestedCalendar.calendar',
+  'get nestedCalendar.Symbol(Symbol.toPrimitive)',
+  'get nestedCalendar.toString',
+  'call nestedCalendar.toString'
+];
+const nestedCalendar = new Proxy({
+  toString: function() {
+    actual.push('call nestedCalendar.toString');
+    return 'iso8601';
+  }
+}, {
+  has(target, property) {
+    actual.push(`has nestedCalendar.${String(property)}`);
+    return property in target;
+  },
+  get(target, property) {
+    actual.push(`get nestedCalendar.${String(property)}`);
+    return target[property];
+  },
+});
+const calendar = new Proxy({
+  calendar: nestedCalendar,
+  toString: function() {
+    actual.push('call calendar.toString');
+    return 'iso8601';
+  },
+}, {
+  has(target, property) {
+    actual.push(`has calendar.${String(property)}`);
+    return property in target;
+  },
+  get(target, property) {
+    actual.push(`get calendar.${String(property)}`);
+    return target[property];
+  },
+});
+
+Object.defineProperty(Temporal.Calendar, 'from', {
+  get() {
+    actual.push('get Temporal.Calendar.from');
+    return undefined;
+  },
+});
+
+Temporal.now.plainDateTime(calendar);
+
+assert.compareArray(actual, expected);

test/built-ins/Temporal/now/plainDateTime/calendar-temporal-object.js

@@ -0,0 +1,22 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Fast path for converting other Temporal objects to Temporal.Calendar by reading internal slots
+info: |
+    sec-temporal.now.plaindatetime step 1:
+      1. Return ? SystemDateTime(_temporalTimeZoneLike_, _calendar_).
+    sec-temporal-systemdatetime step 3:
+      3. Let _calendar_ be ? ToTemporalCalendar(_calendarLike_).
+    sec-temporal-totemporalcalendar step 1.a:
+      a. If _temporalCalendarLike_ has an [[InitializedTemporalDate]], [[InitializedTemporalDateTime]], [[InitializedTemporalMonthDay]], [[InitializedTemporalYearMonth]], or [[InitializedTemporalZonedDateTime]] internal slot, then
+        i. Return _temporalCalendarLike_.[[Calendar]].
+includes: [compareArray.js, temporalHelpers.js]
+features: [Temporal]
+---*/
+
+TemporalHelpers.checkToTemporalCalendarFastPath((temporalObject, calendar) => {
+  const result = Temporal.now.plainDateTime(temporalObject);
+  assert.sameValue(result.calendar, calendar, "Temporal object coerced to calendar");
+});

test/built-ins/Temporal/now/plainDateTime/extensible.js

@@ -0,0 +1,9 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Temporal.now.plainDateTime is extensible.
+features: [Temporal]
+---*/
+
+assert(Object.isExtensible(Temporal.now.plainDateTime));

test/built-ins/Temporal/now/plainDateTime/length.js

@@ -0,0 +1,25 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: The `length` property of Temporal.now.plainDateTime
+info: |
+    Every built-in function object, including constructors, has a "length" property whose value is
+    an integer. Unless otherwise specified, this value is equal to the largest number of named
+    arguments shown in the subclause headings for the function description. Optional parameters
+    (which are indicated with brackets: [ ]) or rest parameters (which are shown using the form
+    «...name») are not included in the default argument count.
+
+    Unless otherwise specified, the "length" property of a built-in function object has the
+    attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+verifyProperty(Temporal.now.plainDateTime, "length", {
+  value: 1,
+  writable: false,
+  enumerable: false,
+  configurable: true,
+});

test/built-ins/Temporal/now/plainDateTime/name.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plainDateTime
+description: Temporal.now.plainDateTime.name is "plainDateTime".
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+assert.sameValue(Temporal.now.plainDateTime.name, 'plainDateTime');
+
+verifyProperty(Temporal.now.plainDateTime, 'name', {
+  enumerable: false,
+  writable: false,
+  configurable: true
+});

test/built-ins/Temporal/now/plainDateTime/not-a-constructor.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Temporal.now.plainDateTime does not implement [[Construct]]
+includes: [isConstructor.js]
+features: [Reflect.construct, Temporal]
+---*/
+
+assert.sameValue(isConstructor(Temporal.now.plainDateTime), false, 'isConstructor(Temporal.now.plainDateTime) must return false');
+
+assert.throws(TypeError, () => {
+  new Temporal.now.plainDateTime();
+}, '`new Temporal.now.plainDateTime()` throws TypeError');

test/built-ins/Temporal/now/plainDateTime/prop-desc.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: The "plainDateTime" property of Temporal.now
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+verifyProperty(Temporal.now, 'plainDateTime', {
+  enumerable: false,
+  writable: true,
+  configurable: true
+});

test/built-ins/Temporal/now/plainDateTime/return-value.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Return value describes the start of a day
+features: [Temporal]
+---*/
+
+const calendar = Temporal.Calendar.from("iso8601");
+const timeZone = {
+  getOffsetNanosecondsFor(instant) {
+    return -Number(instant.epochNanoseconds % 86400_000_000_000n);
+  }
+};
+
+const result = Temporal.now.plainDateTime(calendar, timeZone);
+for (const property of ["hour", "minute", "second", "millisecond", "microsecond", "nanosecond"]) {
+  assert.sameValue(result[property], 0, property);
+}

test/built-ins/Temporal/now/plainDateTime/time-zone-undefined.js

@@ -0,0 +1,29 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Functions when time zone argument is omitted
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const actual = [];
+const expected = [];
+
+Object.defineProperty(Temporal.TimeZone, "from", {
+  get() {
+    actual.push("get Temporal.TimeZone.from");
+    return undefined;
+  },
+});
+
+const resultExplicit = Temporal.now.plainDateTime("iso8601", undefined);
+assert(resultExplicit instanceof Temporal.PlainDateTime);
+
+assert.compareArray(actual, expected, "Temporal.TimeZone.from should not be called");
+
+const resultImplicit = Temporal.now.plainDateTime("iso8601");
+assert(resultImplicit instanceof Temporal.PlainDateTime);
+
+assert.compareArray(actual, expected, "Temporal.TimeZone.from should not be called");

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-invocation.js

@@ -0,0 +1,25 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Correctly invokes `getOffsetNanosecondsFor` method of TimeZone-like objects
+features: [Temporal]
+---*/
+
+var calls = [];
+var timeZone = {
+  getOffsetNanosecondsFor: function() {
+    calls.push({
+      args: arguments,
+      this: this
+    });
+    return 0;
+  },
+};
+
+Temporal.now.plainDateTime('iso8601', timeZone);
+
+assert.sameValue(calls.length, 1, 'call count');
+assert.sameValue(calls[0].args.length, 1, 'arguments');
+assert(calls[0].args[0] instanceof Temporal.Instant);
+assert.sameValue(calls[0].this, timeZone);

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-non-integer.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: RangeError thrown if time zone reports an offset that is not an integer number of nanoseconds
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+[3600_000_000_000.5, NaN].forEach((wrongOffset) => {
+  const timeZone = TemporalHelpers.specificOffsetTimeZone(wrongOffset);
+
+  assert.throws(RangeError, () => Temporal.now.plainDateTime("iso8601", timeZone));
+});

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-non-method.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Rejects when `getOffsetNanosecondsFor` property is not a method
+features: [Temporal]
+---*/
+
+var timeZone = {
+  getOffsetNanosecondsFor: 7
+};
+
+assert.throws(TypeError, function() {
+  Temporal.now.plainDateTime('iso8601', timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-not-a-number.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Rejects non-numeric nanosecond values reported by TimeZone-like object
+features: [Temporal]
+---*/
+
+const invalidValues = [
+  undefined,
+  null,
+  true,
+  "2020-01-01T12:45:36",
+  Symbol(),
+  2n,
+  {},
+  Temporal.PlainDateTime,
+  Temporal.PlainDateTime.prototype,
+];
+
+for (const dateTime of invalidValues) {
+  let callCount = 0;
+  const timeZone = {
+    getOffsetNanosecondsFor(instant, calendar) {
+      callCount += 1;
+      return dateTime;
+    },
+  };
+
+  assert.throws(TypeError, () => Temporal.now.plainDateTime("iso8601", timeZone));
+  assert.sameValue(callCount, 1, 'Invoked `getOffsetNanosecondsFor`');
+}

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-out-of-range.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: RangeError thrown if time zone reports an offset that is out of range
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+[-86400_000_000_001, 86400_000_000_001, -Infinity, Infinity].forEach((wrongOffset) => {
+  const timeZone = TemporalHelpers.specificOffsetTimeZone(wrongOffset);
+
+  assert.throws(RangeError, () => Temporal.now.plainDateTime("iso8601", timeZone));
+});

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-poisoned.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error when accessing `getOffsetNanosecondsFor` property throws
+features: [Temporal]
+---*/
+
+var timeZone = {
+  get getOffsetNanosecondsFor() {
+    throw new Test262Error();
+  }
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime('iso8601', timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-throws.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error when `getOffsetNanosecondsFor` throws
+features: [Temporal]
+---*/
+
+var timeZone = {
+  getOffsetNanosecondsFor() {
+    throw new Test262Error();
+  }
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime('iso8601', timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-getoffsetnanosecondsfor-wrong-type.js

@@ -0,0 +1,24 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: TypeError thrown if time zone reports an offset that is not a Number
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+[
+  undefined,
+  null,
+  true,
+  "+01:00",
+  Symbol(),
+  3600_000_000_000n,
+  {},
+  { valueOf() { return 3600_000_000_000; } },
+].forEach((wrongOffset) => {
+  const timeZone = TemporalHelpers.specificOffsetTimeZone(wrongOffset);
+
+  assert.throws(TypeError, () => Temporal.now.plainDateTime("iso8601", timeZone));
+});

test/built-ins/Temporal/now/plainDateTime/timezone-object-fail-call-tostring.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by invoking "toString" property
+features: [Temporal]
+---*/
+
+var timeZone = {
+  timeZone: {
+    timeZone: true,
+    toString: function() {
+      throw new Test262Error();
+    },
+  }
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime("iso8601", timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-object-fail-get-timezone.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by retrieving value of "timeZone" property
+features: [Temporal]
+---*/
+
+var timeZone = {
+  get timeZone() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime("iso8601", timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-object-fail-has-nested-timezone.js

@@ -0,0 +1,21 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by checking presence of nested "timeZone" property
+features: [Temporal]
+---*/
+
+var timeZone = {
+  timeZone: new Proxy({}, {
+    has: function(target, property) {
+      if (property === 'timeZone') {
+        throw new Test262Error();
+      }
+    },
+  })
+};
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime("iso8601", timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-object-fail-has-timezone.js

@@ -0,0 +1,19 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Forwards error thrown by checking presence of "timeZone" property
+features: [Temporal]
+---*/
+
+var timeZone = new Proxy({}, {
+  has: function(target, property) {
+    if (property === 'timeZone') {
+      throw new Test262Error();
+    }
+  },
+});
+
+assert.throws(Test262Error, function() {
+  Temporal.now.plainDateTime("iso8601", timeZone);
+});

test/built-ins/Temporal/now/plainDateTime/timezone-object.js

@@ -0,0 +1,62 @@
+// Copyright (C) 2020 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Observable interactions with the provided timezone-like object
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const actual = [];
+const expected = [
+  "has timeZone.timeZone",
+  "get timeZone.timeZone",
+  "has nestedTimeZone.timeZone",
+  "get nestedTimeZone.getOffsetNanosecondsFor",
+  "call nestedTimeZone.getOffsetNanosecondsFor",
+];
+const nestedTimeZone = new Proxy({
+  getOffsetNanosecondsFor(instant) {
+    actual.push("call nestedTimeZone.getOffsetNanosecondsFor");
+    assert.sameValue(instant instanceof Temporal.Instant, true, "Instant");
+    return -Number(instant.epochNanoseconds % 86400_000_000_000n);
+  },
+}, {
+  has(target, property) {
+    actual.push(`has nestedTimeZone.${String(property)}`);
+    return property in target;
+  },
+  get(target, property) {
+    actual.push(`get nestedTimeZone.${String(property)}`);
+    return target[property];
+  },
+});
+const timeZone = new Proxy({
+  timeZone: nestedTimeZone,
+  getOffsetNanosecondsFor(instant) {
+    actual.push("call timeZone.getOffsetNanosecondsFor");
+    assert.sameValue(instant instanceof Temporal.Instant, true, "Instant");
+    return -Number(instant.epochNanoseconds % 86400_000_000_000n);
+  },
+}, {
+  has(target, property) {
+    actual.push(`has timeZone.${property}`);
+    return property in target;
+  },
+  get(target, property) {
+    actual.push(`get timeZone.${property}`);
+    return target[property];
+  },
+});
+
+Object.defineProperty(Temporal.TimeZone, "from", {
+  get() {
+    actual.push("get Temporal.TimeZone.from");
+    return undefined;
+  },
+});
+
+Temporal.now.plainDateTime("iso8601", timeZone);
+
+assert.compareArray(actual, expected);