LibJS: Implement Temporal.Calendar.prototype.mergeFields()

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -266,6 +266,7 @@ namespace JS {
     P(log10)                                 \
     P(map)                                   \
     P(max)                                   \
+    P(mergeFields)                           \
     P(message)                               \
     P(microsecond)                           \
     P(microseconds)                          \

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp

@@ -968,4 +968,92 @@ u8 iso_day(Object& temporal_object)
     VERIFY_NOT_REACHED();
 }
 
+// 12.1.45 DefaultMergeFields ( fields, additionalFields ), https://tc39.es/proposal-temporal/#sec-temporal-defaultmergefields
+Object* default_merge_fields(GlobalObject& global_object, Object& fields, Object& additional_fields)
+{
+    auto& vm = global_object.vm();
+
+    // 1. Let merged be ! OrdinaryObjectCreate(%Object.prototype%).
+    auto* merged = Object::create(global_object, global_object.object_prototype());
+
+    // 2. Let originalKeys be ? EnumerableOwnPropertyNames(fields, key).
+    auto original_keys = fields.enumerable_own_property_names(Object::PropertyKind::Key);
+    if (vm.exception())
+        return {};
+
+    // 3. For each element nextKey of originalKeys, do
+    for (auto& next_key : original_keys) {
+        // a. If nextKey is not "month" or "monthCode", then
+        if (next_key.as_string().string() != vm.names.month.as_string() && next_key.as_string().string() != vm.names.monthCode.as_string()) {
+            auto property_name = PropertyName::from_value(global_object, next_key);
+
+            // i. Let propValue be ? Get(fields, nextKey).
+            auto prop_value = fields.get(property_name);
+            if (vm.exception())
+                return {};
+
+            // ii. If propValue is not undefined, then
+            if (!prop_value.is_undefined()) {
+                // 1. Perform ! CreateDataPropertyOrThrow(merged, nextKey, propValue).
+                merged->create_data_property_or_throw(property_name, prop_value);
+            }
+        }
+    }
+
+    // 4. Let newKeys be ? EnumerableOwnPropertyNames(additionalFields, key).
+    auto new_keys = additional_fields.enumerable_own_property_names(Object::PropertyKind::Key);
+    if (vm.exception())
+        return {};
+
+    // IMPLEMENTATION DEFINED: This is an optimization, so we don't have to iterate new_keys three times (worst case), but only once.
+    bool new_keys_contains_month_or_month_code_property = false;
+
+    // 5. For each element nextKey of newKeys, do
+    for (auto& next_key : new_keys) {
+        auto property_name = PropertyName::from_value(global_object, next_key);
+
+        // a. Let propValue be ? Get(additionalFields, nextKey).
+        auto prop_value = additional_fields.get(property_name);
+        if (vm.exception())
+            return {};
+
+        // b. If propValue is not undefined, then
+        if (!prop_value.is_undefined()) {
+            // i. Perform ! CreateDataPropertyOrThrow(merged, nextKey, propValue).
+            merged->create_data_property_or_throw(property_name, prop_value);
+        }
+
+        // See comment above.
+        new_keys_contains_month_or_month_code_property |= next_key.as_string().string() == vm.names.month.as_string() || next_key.as_string().string() == vm.names.monthCode.as_string();
+    }
+
+    // 6. If newKeys does not contain either "month" or "monthCode", then
+    if (!new_keys_contains_month_or_month_code_property) {
+        // a. Let month be ? Get(fields, "month").
+        auto month = fields.get(vm.names.month);
+        if (vm.exception())
+            return {};
+
+        // b. If month is not undefined, then
+        if (!month.is_undefined()) {
+            // i. Perform ! CreateDataPropertyOrThrow(merged, "month", month).
+            merged->create_data_property_or_throw(vm.names.month, month);
+        }
+
+        // c. Let monthCode be ? Get(fields, "monthCode").
+        auto month_code = fields.get(vm.names.monthCode);
+        if (vm.exception())
+            return {};
+
+        // d. If monthCode is not undefined, then
+        if (!month_code.is_undefined()) {
+            // i. Perform ! CreateDataPropertyOrThrow(merged, "monthCode", monthCode).
+            merged->create_data_property_or_throw(vm.names.monthCode, month_code);
+        }
+    }
+
+    // 7. Return merged.
+    return merged;
+}
+
 }

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h

@@ -69,5 +69,6 @@ i32 iso_year(Object& temporal_object);
 u8 iso_month(Object& temporal_object);
 String iso_month_code(Object& temporal_object);
 u8 iso_day(Object& temporal_object);
+Object* default_merge_fields(GlobalObject&, Object& fields, Object& additional_fields);
 
 }

Userland/Libraries/LibJS/Runtime/Temporal/CalendarPrototype.cpp

@@ -50,6 +50,7 @@ void CalendarPrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.monthsInYear, months_in_year, 1, attr);
     define_native_function(vm.names.inLeapYear, in_leap_year, 1, attr);
     define_native_function(vm.names.fields, fields, 1, attr);
+    define_native_function(vm.names.mergeFields, merge_fields, 2, attr);
     define_native_function(vm.names.toString, to_string, 0, attr);
     define_native_function(vm.names.toJSON, to_json, 0, attr);
 }
@@ -507,6 +508,33 @@ JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::fields)
     return Array::create_from(global_object, field_names);
 }
 
+// 12.4.22 Temporal.Calendar.prototype.mergeFields ( fields, additionalFields ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.mergefields
+// NOTE: This is the minimum mergeFields implementation for engines without ECMA-402.
+JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::merge_fields)
+{
+    // 1. Let calendar be the this value.
+    // 2. Perform ? RequireInternalSlot(calendar, [[InitializedTemporalCalendar]]).
+    auto* calendar = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Assert: calendar.[[Identifier]] is "iso8601".
+    VERIFY(calendar->identifier() == "iso8601"sv);
+
+    // 4. Set fields to ? ToObject(fields).
+    auto* fields = vm.argument(0).to_object(global_object);
+    if (vm.exception())
+        return {};
+
+    // 5. Set additionalFields to ? ToObject(additionalFields).
+    auto* additional_fields = vm.argument(1).to_object(global_object);
+    if (vm.exception())
+        return {};
+
+    // 6. Return ? DefaultMergeFields(fields, additionalFields).
+    return default_merge_fields(global_object, *fields, *additional_fields);
+}
+
 // 12.4.23 Temporal.Calendar.prototype.toString ( ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.tostring
 JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::to_string)
 {

Userland/Libraries/LibJS/Runtime/Temporal/CalendarPrototype.h

@@ -36,6 +36,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(months_in_year);
     JS_DECLARE_NATIVE_FUNCTION(in_leap_year);
     JS_DECLARE_NATIVE_FUNCTION(fields);
+    JS_DECLARE_NATIVE_FUNCTION(merge_fields);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(to_json);
 };

Userland/Libraries/LibJS/Tests/builtins/Temporal/Calendar/Calendar.prototype.mergeFields.js

@@ -0,0 +1,54 @@
+describe("correct behavior", () => {
+    test("length is 2", () => {
+        expect(Temporal.Calendar.prototype.mergeFields).toHaveLength(2);
+    });
+
+    test("basic functionality", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        const fields = {};
+        const additionalFields = {};
+        const mergedFields = calendar.mergeFields(fields, additionalFields);
+        expect(mergedFields).not.toBe(fields);
+        expect(mergedFields).not.toBe(additionalFields);
+        expect(mergedFields).toEqual({});
+        expect(Object.getPrototypeOf(mergedFields)).toBe(Object.prototype);
+        expect(calendar.mergeFields({ foo: 1, bar: 1 }, { foo: 2 })).toEqual({ foo: 2, bar: 1 });
+        expect(calendar.mergeFields({ foo: 1 }, { foo: 2, bar: 2 })).toEqual({ foo: 2, bar: 2 });
+        expect(calendar.mergeFields({ foo: 1 }, { foo: 2, bar: 2 })).toEqual({ foo: 2, bar: 2 });
+    });
+
+    test("month and monthCode property handling", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(calendar.mergeFields({ month: 1 }, { monthCode: 2 })).toEqual({ monthCode: 2 });
+        expect(calendar.mergeFields({ monthCode: 1 }, { month: 2 })).toEqual({ month: 2 });
+        expect(calendar.mergeFields({ month: 1, monthCode: 1 }, {})).toEqual({
+            month: 1,
+            monthCode: 1,
+        });
+        expect(
+            calendar.mergeFields({ month: 1, monthCode: 1 }, { month: 2, monthCode: 2 })
+        ).toEqual({ month: 2, monthCode: 2 });
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.Calendar object", () => {
+        expect(() => {
+            Temporal.Calendar.prototype.mergeFields.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.Calendar");
+    });
+
+    test("fields argument must be coercible to object", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.mergeFields(null, {});
+        }).toThrowWithMessage(TypeError, "ToObject on null or undefined");
+    });
+
+    test("additionalFields argument must be coercible to object", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.mergeFields({}, null);
+        }).toThrowWithMessage(TypeError, "ToObject on null or undefined");
+    });
+});