LibJS: Implement Intl.ListFormat.prototype.format

7 files changed, 517 insertions, 0 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h b/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
index b5faf7e375..54e3373825 100644
--- a/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
+++ b/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
@@ -167,6 +167,7 @@ namespace JS {
     P(fontcolor)                             \
     P(fontsize)                              \
     P(forEach)                               \
+    P(format)                                \
     P(fractionalSecondDigits)                \
     P(freeze)                                \
     P(from)                                  \
diff --git a/Userland/Libraries/LibJS/Runtime/ErrorTypes.h b/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
index 17f13df4ef..0fa9093796 100644
--- a/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
+++ b/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
@@ -62,6 +62,7 @@
     M(NotAnObject, "{} is not an object")                                                                                               \
     M(NotAnObjectOrNull, "{} is neither an object nor null")                                                                            \
     M(NotAnObjectOrString, "{} is neither an object nor a string")                                                                      \
+    M(NotAString, "{} is not a string")                                                                                                 \
     M(NotASymbol, "{} is not a symbol")                                                                                                 \
     M(NotIterable, "{} is not iterable")                                                                                                \
     M(NotObjectCoercible, "{} cannot be converted to an object")                                                                        \
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp b/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
index 0cb86bdaca..5c4a7373f2 100644
--- a/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
@@ -536,6 +536,65 @@ Value get_option(GlobalObject& global_object, Value options, PropertyName const&
     return value;
 }
 
+// 9.2.16 PartitionPattern ( pattern ), https://tc39.es/ecma402/#sec-partitionpattern
+Vector<PatternPartition> partition_pattern(StringView pattern)
+{
+    // 1. Let result be a new empty List.
+    Vector<PatternPartition> result;
+
+    // 2. Let beginIndex be ! StringIndexOf(pattern, "{", 0).
+    auto begin_index = pattern.find('{', 0);
+
+    // 3. Let endIndex be 0.
+    size_t end_index = 0;
+
+    // 4. Let nextIndex be 0.
+    size_t next_index = 0;
+
+    // 5. Let length be the number of code units in pattern.
+    // 6. Repeat, while beginIndex is an integer index into pattern,
+    while (begin_index.has_value()) {
+        // a. Set endIndex to ! StringIndexOf(pattern, "}", beginIndex).
+        end_index = pattern.find('}', *begin_index).value();
+
+        // b. Assert: endIndex is greater than beginIndex.
+        VERIFY(end_index > *begin_index);
+
+        // c. If beginIndex is greater than nextIndex, then
+        if (*begin_index > next_index) {
+            // i. Let literal be a substring of pattern from position nextIndex, inclusive, to position beginIndex, exclusive.
+            auto literal = pattern.substring_view(next_index, *begin_index - next_index);
+
+            // ii. Append a new Record { [[Type]]: "literal", [[Value]]: literal } as the last element of the list result.
+            result.append({ "literal"sv, literal });
+        }
+
+        // d. Let p be the substring of pattern from position beginIndex, exclusive, to position endIndex, exclusive.
+        auto partition = pattern.substring_view(*begin_index + 1, end_index - *begin_index - 1);
+
+        // e. Append a new Record { [[Type]]: p, [[Value]]: undefined } as the last element of the list result.
+        result.append({ partition, {} });
+
+        // f. Set nextIndex to endIndex + 1.
+        next_index = end_index + 1;
+
+        // g. Set beginIndex to ! StringIndexOf(pattern, "{", nextIndex).
+        begin_index = pattern.find('{', next_index);
+    }
+
+    // 7. If nextIndex is less than length, then
+    if (next_index < pattern.length()) {
+        // a. Let literal be the substring of pattern from position nextIndex, inclusive, to position length, exclusive.
+        auto literal = pattern.substring_view(next_index);
+
+        // b. Append a new Record { [[Type]]: "literal", [[Value]]: literal } as the last element of the list result.
+        result.append({ "literal"sv, literal });
+    }
+
+    // 8. Return result.
+    return result;
+}
+
 // 12.1.1 CanonicalCodeForDisplayNames ( type, code ), https://tc39.es/ecma402/#sec-canonicalcodefordisplaynames
 Value canonical_code_for_display_names(GlobalObject& global_object, DisplayNames::Type type, StringView code)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.h b/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.h
index 3f089ff33c..b2c7167c26 100644
--- a/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.h
+++ b/Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.h
@@ -26,6 +26,11 @@ struct LocaleResult {
     String locale;
 };
 
+struct PatternPartition {
+    StringView type;
+    StringView value;
+};
+
 Optional<Unicode::LocaleID> is_structurally_valid_language_tag(StringView locale);
 String canonicalize_unicode_locale_id(Unicode::LocaleID& locale);
 Vector<String> canonicalize_locale_list(GlobalObject&, Value locales);
@@ -35,6 +40,7 @@ Vector<String> lookup_supported_locales(Vector<String> const& requested_locales)
 Array* supported_locales(GlobalObject&, Vector<String> const& requested_locales, Value options);
 Object* coerce_options_to_object(GlobalObject& global_object, Value options);
 Value get_option(GlobalObject& global_object, Value options, PropertyName const& property, Value::Type type, Vector<StringView> const& values, Fallback fallback);
+Vector<PatternPartition> partition_pattern(StringView pattern);
 String insert_unicode_extension_and_canonicalize(Unicode::LocaleID locale_id, Unicode::LocaleExtension extension);
 LocaleResult resolve_locale(Vector<String> const& requested_locales, LocaleOptions const& options, Vector<StringView> relevant_extension_keys);
 Value canonical_code_for_display_names(GlobalObject&, DisplayNames::Type type, StringView code);
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.cpp
index 6bde36f714..769424e0f7 100644
--- a/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.cpp
@@ -4,11 +4,248 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/HashMap.h>
+#include <AK/StringBuilder.h>
+#include <AK/TypeCasts.h>
+#include <AK/Variant.h>
+#include <AK/Vector.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Intl/AbstractOperations.h>
+#include <LibJS/Runtime/Intl/ListFormat.h>
 #include <LibJS/Runtime/Intl/ListFormatPrototype.h>
+#include <LibJS/Runtime/IteratorOperations.h>
+#include <LibUnicode/Locale.h>
 
 namespace JS::Intl {
 
+static ListFormat* typed_this(GlobalObject& global_object)
+{
+    auto& vm = global_object.vm();
+
+    auto* this_object = vm.this_value(global_object).to_object(global_object);
+    if (!this_object)
+        return nullptr;
+
+    if (!is<ListFormat>(this_object)) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::NotA, "Intl.ListFormat");
+        return nullptr;
+    }
+
+    return static_cast<ListFormat*>(this_object);
+}
+
+using Placeables = HashMap<StringView, Variant<PatternPartition, Vector<PatternPartition>>>;
+
+// 13.1.1 DeconstructPattern ( pattern, placeables ), https://tc39.es/ecma402/#sec-deconstructpattern
+static Vector<PatternPartition> deconstruct_pattern(StringView pattern, Placeables placeables)
+{
+    // 1. Let patternParts be PartitionPattern(pattern).
+    auto pattern_parts = partition_pattern(pattern);
+
+    // 2. Let result be a new empty List.
+    Vector<PatternPartition> result {};
+
+    // 3. For each Record { [[Type]], [[Value]] } patternPart of patternParts, do
+    for (auto const& pattern_part : pattern_parts) {
+        // a. Let part be patternPart.[[Type]].
+        auto part = pattern_part.type;
+
+        // b. If part is "literal", then
+        if (part == "literal"sv) {
+            // i. Append Record { [[Type]]: "literal", [[Value]]: patternPart.[[Value]] } to result.
+            result.append({ part, pattern_part.value });
+        }
+        // c. Else,
+        else {
+            // i. Assert: placeables has a field [[<part>]].
+            // ii. Let subst be placeables.[[<part>]].
+            auto subst = placeables.get(part);
+            VERIFY(subst.has_value());
+
+            subst.release_value().visit(
+                // iii. If Type(subst) is List, then
+                [&](Vector<PatternPartition>& partition) {
+                    // 1. For each element s of subst, do
+                    for (auto& element : partition) {
+                        // a. Append s to result.
+                        result.append(move(element));
+                    }
+                },
+                // iv. Else,
+                [&](PatternPartition& partition) {
+                    // 1. Append subst to result.
+                    result.append(move(partition));
+                });
+        }
+    }
+
+    // 4. Return result.
+    return result;
+}
+
+// 13.1.2 CreatePartsFromList ( listFormat, list ), https://tc39.es/ecma402/#sec-createpartsfromlist
+static Vector<PatternPartition> create_parts_from_list(ListFormat const& list_format, Vector<String> const& list)
+{
+    auto list_patterns = Unicode::get_locale_list_patterns(list_format.locale(), list_format.type_string(), list_format.style_string());
+    if (!list_patterns.has_value())
+        return {};
+
+    // 1. Let size be the number of elements of list.
+    auto size = list.size();
+
+    // 2. If size is 0, then
+    if (size == 0) {
+        // a. Return a new empty List.
+        return {};
+    }
+
+    // 3. If size is 2, then
+    if (size == 2) {
+        // a. Let n be an index into listFormat.[[Templates]] based on listFormat.[[Locale]], list[0], and list[1].
+        // b. Let pattern be listFormat.[[Templates]][n].[[Pair]].
+        auto pattern = list_patterns->pair;
+
+        // c. Let first be a new Record { [[Type]]: "element", [[Value]]: list[0] }.
+        PatternPartition first { "element"sv, list[0] };
+
+        // d. Let second be a new Record { [[Type]]: "element", [[Value]]: list[1] }.
+        PatternPartition second { "element"sv, list[1] };
+
+        // e. Let placeables be a new Record { [[0]]: first, [[1]]: second }.
+        Placeables placeables;
+        placeables.set("0"sv, move(first));
+        placeables.set("1"sv, move(second));
+
+        // f. Return DeconstructPattern(pattern, placeables).
+        return deconstruct_pattern(pattern, move(placeables));
+    }
+
+    // 4. Let last be a new Record { [[Type]]: "element", [[Value]]: list[size - 1] }.
+    PatternPartition last { "element"sv, list[size - 1] };
+
+    // 5. Let parts be « last ».
+    Vector<PatternPartition> parts { move(last) };
+
+    // The spec does not say to do this, but because size_t is unsigned, we need to take care not to wrap around 0.
+    if (size == 1)
+        return parts;
+
+    // 6. Let i be size - 2.
+    size_t i = size - 2;
+
+    // 7. Repeat, while i ≥ 0,
+    do {
+        // a. Let head be a new Record { [[Type]]: "element", [[Value]]: list[i] }.
+        PatternPartition head { "element"sv, list[i] };
+
+        // b. Let n be an implementation-defined index into listFormat.[[Templates]] based on listFormat.[[Locale]], head, and parts.
+        StringView pattern;
+
+        // c. If i is 0, then
+        if (i == 0) {
+            // i. Let pattern be listFormat.[[Templates]][n].[[Start]].
+            pattern = list_patterns->start;
+        }
+        // d. Else if i is less than size - 2, then
+        else if (i < (size - 2)) {
+            // i. Let pattern be listFormat.[[Templates]][n].[[Middle]].
+            pattern = list_patterns->middle;
+        }
+        // e. Else,
+        else {
+            // i. Let pattern be listFormat.[[Templates]][n].[[End]].
+            pattern = list_patterns->end;
+        }
+
+        // f. Let placeables be a new Record { [[0]]: head, [[1]]: parts }.
+        Placeables placeables;
+        placeables.set("0"sv, move(head));
+        placeables.set("1"sv, move(parts));
+
+        // g. Set parts to DeconstructPattern(pattern, placeables).
+        parts = deconstruct_pattern(pattern, move(placeables));
+
+        // h. Decrement i by 1.
+    } while (i-- != 0);
+
+    // 8. Return parts.
+    return parts;
+}
+
+// 13.1.3 FormatList ( listFormat, list )
+static String format_list(ListFormat const& list_format, Vector<String> const& list)
+{
+    // 1. Let parts be CreatePartsFromList(listFormat, list).
+    auto parts = create_parts_from_list(list_format, list);
+
+    // 2. Let result be an empty String.
+    StringBuilder result;
+
+    // 3. For each Record { [[Type]], [[Value]] } part in parts, do
+    for (auto const& part : parts) {
+        // a. Set result to the string-concatenation of result and part.[[Value]].
+        result.append(part.value);
+    }
+
+    // 4. Return result.
+    return result.build();
+}
+
+// 13.1.5 StringListFromIterable ( iterable ), https://tc39.es/ecma402/#sec-createstringlistfromiterable
+static Vector<String> string_list_from_iterable(GlobalObject& global_object, Value iterable)
+{
+    auto& vm = global_object.vm();
+
+    // 1. If iterable is undefined, then
+    if (iterable.is_undefined()) {
+        // a. Return a new empty List.
+        return {};
+    }
+
+    // 2. Let iteratorRecord be ? GetIterator(iterable).
+    auto* iterator_record = get_iterator(global_object, iterable);
+    if (vm.exception())
+        return {};
+
+    // 3. Let list be a new empty List.
+    Vector<String> list;
+
+    // 4. Let next be true.
+    Object* next = nullptr;
+
+    // 5. Repeat, while next is not false,
+    do {
+        // a. Set next to ? IteratorStep(iteratorRecord).
+        next = iterator_step(global_object, *iterator_record);
+        if (vm.exception())
+            return {};
+
+        // b. If next is not false, then
+        if (next != nullptr) {
+            // i. Let nextValue be ? IteratorValue(next).
+            auto next_value = iterator_value(global_object, *next);
+            if (vm.exception())
+                return {};
+
+            // ii. If Type(nextValue) is not String, then
+            if (!next_value.is_string()) {
+                // 1. Let error be ThrowCompletion(a newly created TypeError object).
+                vm.throw_exception<TypeError>(global_object, ErrorType::NotAString, next_value);
+
+                // 2. Return ? IteratorClose(iteratorRecord, error).
+                iterator_close(*iterator_record);
+                return {};
+            }
+
+            // iii. Append nextValue to the end of the List list.
+            list.append(next_value.as_string().string());
+        }
+    } while (next != nullptr);
+
+    // 6. Return list.
+    return list;
+}
+
 // 13.4 Properties of the Intl.ListFormat Prototype Object, https://tc39.es/ecma402/#sec-properties-of-intl-listformat-prototype-object
 ListFormatPrototype::ListFormatPrototype(GlobalObject& global_object)
     : Object(*global_object.object_prototype())
@@ -23,6 +260,30 @@ void ListFormatPrototype::initialize(GlobalObject& global_object)
 
     // 13.4.2 Intl.ListFormat.prototype [ @@toStringTag ], https://tc39.es/ecma402/#sec-Intl.ListFormat.prototype-toStringTag
     define_direct_property(*vm.well_known_symbol_to_string_tag(), js_string(vm, "Intl.ListFormat"), Attribute::Configurable);
+
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.format, format, 1, attr);
+}
+
+// 13.4.3 Intl.ListFormat.prototype.format ( list ), https://tc39.es/ecma402/#sec-Intl.ListFormat.prototype.format
+JS_DEFINE_NATIVE_FUNCTION(ListFormatPrototype::format)
+{
+    auto list = vm.argument(0);
+
+    // 1. Let lf be the this value.
+    // 2. Perform ? RequireInternalSlot(lf, [[InitializedListFormat]]).
+    auto* list_format = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Let stringList be ? StringListFromIterable(list).
+    auto string_list = string_list_from_iterable(global_object, list);
+    if (vm.exception())
+        return {};
+
+    // 4. Return FormatList(lf, stringList).
+    auto formatted = format_list(*list_format, string_list);
+    return js_string(vm, move(formatted));
 }
 
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.h b/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.h
index 6bcbe6cf2f..605db99c11 100644
--- a/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Intl/ListFormatPrototype.h
@@ -17,6 +17,9 @@ public:
     explicit ListFormatPrototype(GlobalObject&);
     virtual void initialize(GlobalObject&) override;
     virtual ~ListFormatPrototype() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(format);
 };
 
 }
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Intl/ListFormat/ListFormat.prototype.format.js b/Userland/Libraries/LibJS/Tests/builtins/Intl/ListFormat/ListFormat.prototype.format.js
new file mode 100644
index 0000000000..de5ad3563e
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Intl/ListFormat/ListFormat.prototype.format.js
@@ -0,0 +1,186 @@
+describe("errors", () => {
+    function SomeError() {}
+
+    test("called on non-ListFormat object", () => {
+        expect(() => {
+            Intl.ListFormat.prototype.format([]);
+        }).toThrowWithMessage(TypeError, "Not a Intl.ListFormat object");
+    });
+
+    test("called with non-string iterable", () => {
+        expect(() => {
+            new Intl.ListFormat().format([1]);
+        }).toThrowWithMessage(TypeError, "1 is not a string");
+    });
+
+    test("called with iterable that throws immediately", () => {
+        let iterable = {
+            [Symbol.iterator]() {
+                throw new SomeError();
+            },
+        };
+
+        expect(() => {
+            new Intl.ListFormat().format(iterable);
+        }).toThrow(SomeError);
+    });
+
+    test("called with iterable that throws on step", () => {
+        let iterable = {
+            [Symbol.iterator]() {
+                return this;
+            },
+            next() {
+                throw new SomeError();
+            },
+        };
+
+        expect(() => {
+            new Intl.ListFormat().format(iterable);
+        }).toThrow(SomeError);
+    });
+
+    test("called with iterable that throws on value resolution", () => {
+        let iterable = {
+            [Symbol.iterator]() {
+                return this;
+            },
+            next() {
+                return {
+                    done: false,
+                    get value() {
+                        throw new SomeError();
+                    },
+                };
+            },
+        };
+
+        expect(() => {
+            new Intl.ListFormat().format(iterable);
+        }).toThrow(SomeError);
+    });
+});
+
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Intl.ListFormat.prototype.format).toHaveLength(1);
+    });
+
+    test("undefined list returns empty string", () => {
+        expect(new Intl.ListFormat().format(undefined)).toBe("");
+    });
+});
+
+describe("type=conjunction", () => {
+    test("style=long", () => {
+        let en = new Intl.ListFormat("en", { type: "conjunction", style: "long" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a and b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, and c");
+
+        let es = new Intl.ListFormat("es-419", { type: "conjunction", style: "long" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a y b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b y c");
+    });
+
+    test("style=short", () => {
+        let en = new Intl.ListFormat("en", { type: "conjunction", style: "short" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a & b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, & c");
+
+        let es = new Intl.ListFormat("es-419", { type: "conjunction", style: "short" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a y b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b y c");
+    });
+
+    test("style=narrow", () => {
+        let en = new Intl.ListFormat("en", { type: "conjunction", style: "narrow" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a, b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, c");
+
+        let es = new Intl.ListFormat("es-419", { type: "conjunction", style: "narrow" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a y b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b y c");
+    });
+});
+
+describe("type=disjunction", () => {
+    test("style=long", () => {
+        let en = new Intl.ListFormat("en", { type: "disjunction", style: "long" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a or b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, or c");
+
+        let es = new Intl.ListFormat("es-419", { type: "disjunction", style: "long" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a o b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b o c");
+    });
+
+    test("style=short", () => {
+        let en = new Intl.ListFormat("en", { type: "disjunction", style: "short" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a or b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, or c");
+
+        let es = new Intl.ListFormat("es-419", { type: "disjunction", style: "short" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a o b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b o c");
+    });
+
+    test("style=narrow", () => {
+        let en = new Intl.ListFormat("en", { type: "disjunction", style: "narrow" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a or b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, or c");
+
+        let es = new Intl.ListFormat("es-419", { type: "disjunction", style: "narrow" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a o b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b o c");
+    });
+});
+
+describe("type=unit", () => {
+    test("style=long", () => {
+        let en = new Intl.ListFormat("en", { type: "unit", style: "long" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a, b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, c");
+
+        let es = new Intl.ListFormat("es-419", { type: "unit", style: "long" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a y b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b y c");
+    });
+
+    test("style=short", () => {
+        let en = new Intl.ListFormat("en", { type: "unit", style: "short" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a, b");
+        expect(en.format(["a", "b", "c"])).toBe("a, b, c");
+
+        let es = new Intl.ListFormat("es-419", { type: "unit", style: "short" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a y b");
+        expect(es.format(["a", "b", "c"])).toBe("a, b, c");
+    });
+
+    test("style=narrow", () => {
+        let en = new Intl.ListFormat("en", { type: "unit", style: "narrow" });
+        expect(en.format(["a"])).toBe("a");
+        expect(en.format(["a", "b"])).toBe("a b");
+        expect(en.format(["a", "b", "c"])).toBe("a b c");
+
+        let es = new Intl.ListFormat("es-419", { type: "unit", style: "narrow" });
+        expect(es.format(["a"])).toBe("a");
+        expect(es.format(["a", "b"])).toBe("a b");
+        expect(es.format(["a", "b", "c"])).toBe("a b c");
+    });
+});