LibJS: Implement Temporal.Duration.prototype.days

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -101,6 +101,7 @@ namespace JS {
     P(count)                                 \
     P(countReset)                            \
     P(create)                                \
+    P(days)                                  \
     P(debug)                                 \
     P(decodeURI)                             \
     P(decodeURIComponent)                    \

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

@@ -28,6 +28,7 @@ void DurationPrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.years, years_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.months, months_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.weeks, weeks_getter, {}, Attribute::Configurable);
+    define_native_accessor(vm.names.days, days_getter, {}, Attribute::Configurable);
 }
 
 static Duration* typed_this(GlobalObject& global_object)
@@ -82,4 +83,17 @@ JS_DEFINE_NATIVE_FUNCTION(DurationPrototype::weeks_getter)
     return Value(duration->weeks());
 }
 
+// 7.3.6 get Temporal.Duration.prototype.days, https://tc39.es/proposal-temporal/#sec-get-temporal.duration.prototype.days
+JS_DEFINE_NATIVE_FUNCTION(DurationPrototype::days_getter)
+{
+    // 1. Let duration be the this value.
+    // 2. Perform ? RequireInternalSlot(duration, [[InitializedTemporalDuration]]).
+    auto* duration = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Return duration.[[Days]].
+    return Value(duration->days());
+}
+
 }

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

@@ -22,6 +22,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(years_getter);
     JS_DECLARE_NATIVE_FUNCTION(months_getter);
     JS_DECLARE_NATIVE_FUNCTION(weeks_getter);
+    JS_DECLARE_NATIVE_FUNCTION(days_getter);
 };
 
 }

Userland/Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.prototype.days.js

@@ -0,0 +1,14 @@
+describe("correct behavior", () => {
+    test("basic functionality", () => {
+        const duration = new Temporal.Duration(0, 0, 0, 123);
+        expect(duration.days).toBe(123);
+    });
+});
+
+test("errors", () => {
+    test("this value must be a Temporal.Duration object", () => {
+        expect(() => {
+            Reflect.get(Temporal.Duration.prototype, "days", "foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.Duration");
+    });
+});