From 67b3255fe84324e384a52e19fb5233ccb3665c1d Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Mon, 26 Jul 2021 17:07:59 +0300
Subject: [PATCH] LibJS: Implement Temporal.PlainDate.from

---
 .../Runtime/Temporal/PlainDateConstructor.cpp | 25 +++++++++++++++++++
 .../Runtime/Temporal/PlainDateConstructor.h   |  1 +
 .../Temporal/PlainDate/PlainDate.from.js      | 21 ++++++++++++++++
 3 files changed, 47 insertions(+)
 create mode 100644 Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.from.js

diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
index b6f38b2d6b..b5b52546eb 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
@@ -28,6 +28,7 @@ void PlainDateConstructor::initialize(GlobalObject& global_object)
     define_direct_property(vm.names.prototype, global_object.temporal_plain_date_prototype(), 0);
 
     u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.from, from, 1, attr);
     define_native_function(vm.names.compare, compare, 2, attr);
 
     define_direct_property(vm.names.length, Value(3), Attribute::Configurable);
@@ -96,6 +97,30 @@ Value PlainDateConstructor::construct(FunctionObject& new_target)
     return create_temporal_date(global_object, y, m, d, *calendar, &new_target);
 }
 
+// 3.2.2 Temporal.PlainDate.from ( item [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.from
+JS_DEFINE_NATIVE_FUNCTION(PlainDateConstructor::from)
+{
+    // 1. Set options to ? GetOptionsObject(options).
+    auto* options = get_options_object(global_object, vm.argument(1));
+    if (vm.exception())
+        return {};
+
+    auto item = vm.argument(0);
+    // 2. If Type(item) is Object and item has an [[InitializedTemporalDate]] internal slot, then
+    if (item.is_object() && is<PlainDate>(item.as_object())) {
+        auto& plain_date_item = static_cast<PlainDate&>(item.as_object());
+        // a. Perform ? ToTemporalOverflow(options).
+        (void)to_temporal_overflow(global_object, *options);
+        if (vm.exception())
+            return {};
+        // b. Return ? CreateTemporalDate(item.[[ISOYear]], item.[[ISOMonth]], item.[[ISODay]], item.[[Calendar]]).
+        return create_temporal_date(global_object, plain_date_item.iso_year(), plain_date_item.iso_month(), plain_date_item.iso_day(), plain_date_item.calendar());
+    }
+
+    // 3. Return ? ToTemporalDate(item, options).
+    return to_temporal_date(global_object, item, options);
+}
+
 // 3.2.3 Temporal.PlainDate.compare ( one, two ), https://tc39.es/proposal-temporal/#sec-properties-of-the-temporal-plaindate-constructor
 JS_DEFINE_NATIVE_FUNCTION(PlainDateConstructor::compare)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.h b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.h
index e02a3153c4..4a0d6ab6df 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.h
@@ -24,6 +24,7 @@ public:
 private:
     virtual bool has_constructor() const override { return true; }
 
+    JS_DECLARE_NATIVE_FUNCTION(from);
     JS_DECLARE_NATIVE_FUNCTION(compare);
 };
 
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.from.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.from.js
new file mode 100644
index 0000000000..d6f5730656
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.from.js
@@ -0,0 +1,21 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainDate.from).toHaveLength(1);
+    });
+
+    test("PlainDate instance argument", () => {
+        const plainDate = new Temporal.PlainDate(2021, 7, 26);
+        const createdPlainDate = Temporal.PlainDate.from(plainDate);
+        expect(createdPlainDate.year).toBe(2021);
+        expect(createdPlainDate.month).toBe(7);
+        expect(createdPlainDate.day).toBe(26);
+    });
+
+    // Un-skip once ParseISODateTime & ParseTemporalDateString are implemented
+    test.skip("PlainDate string argument", () => {
+        const createdPlainDate = Temporal.PlainDate.from("2021-07-26");
+        expect(createdPlainDate.year).toBe(2021);
+        expect(createdPlainDate.month).toBe(7);
+        expect(createdPlainDate.day).toBe(26);
+    });
+});