LibWeb: Add support for indexed setter of HTMLOptionsCollection

Tests/LibWeb/Ref/options-set-index.html

@@ -0,0 +1,7 @@
+<link rel="match" href="reference/options-set-index.html" />
+<select id="select"></select>
+<script>
+    const select = document.getElementById("select");
+    select.options[0] = new Option("text");
+    select.value = "text";
+</script>

Tests/LibWeb/Ref/reference/options-set-index.html

@@ -0,0 +1 @@
+<select><option>text</option></select>

Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.cpp

@@ -26,6 +26,8 @@ JS::NonnullGCPtr<HTMLOptionsCollection> HTMLOptionsCollection::create(DOM::Paren
 HTMLOptionsCollection::HTMLOptionsCollection(DOM::ParentNode& root, Function<bool(DOM::Element const&)> filter)
     : DOM::HTMLCollection(root, Scope::Descendants, move(filter))
 {
+    m_legacy_platform_object_flags->has_indexed_property_setter = true;
+    m_legacy_platform_object_flags->indexed_property_setter_has_identifier = true;
 }
 
 HTMLOptionsCollection::~HTMLOptionsCollection() = default;
@@ -71,6 +73,52 @@ WebIDL::ExceptionOr<void> HTMLOptionsCollection::set_length(WebIDL::UnsignedLong
     return {};
 }
 
+// https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-htmloptionscollection-setter
+WebIDL::ExceptionOr<void> HTMLOptionsCollection::set_value_of_indexed_property(u32 index, JS::Value unconverted_option)
+{
+    // The spec doesn't seem to require this, but it's consistent with length handling and other browsers
+    if (index > 100'000) {
+        return {};
+    }
+
+    // 1. If value is null, invoke the steps for the remove method with index as the argument, and return.
+    if (unconverted_option.is_null()) {
+        remove(static_cast<WebIDL::Long>(index));
+        return {};
+    }
+
+    if (!unconverted_option.is_object() || !is<HTMLOptionElement>(unconverted_option.as_object())) {
+        return WebIDL::TypeMismatchError::create(realm(), "The value provided is not an HTMLOptionElement"_fly_string);
+    }
+
+    auto& option = dynamic_cast<HTMLOptionElement&>(unconverted_option.as_object());
+
+    // 2. Let length be the number of nodes represented by the collection.
+    auto length = this->length();
+
+    auto root_element = root();
+
+    if (index >= length) {
+        // 3. Let n be index minus length.
+        auto n = index - length;
+
+        // 4. If n is greater than zero, then append a DocumentFragment consisting of n-1 new option elements with no attributes and no child nodes to the select element on which the HTMLOptionsCollection is rooted.
+        if (n > 0) {
+            for (WebIDL::UnsignedLong i = 0; i < n - 1; i++) {
+                TRY(root_element->append_child(TRY(DOM::create_element(root_element->document(), HTML::TagNames::option, Namespace::HTML))));
+            }
+        }
+
+        // 5. If n is greater than or equal to zero, append value to the select element.
+        TRY(root_element->append_child(option));
+    } else {
+        // 5 (cont). Otherwise, replace the indexth element in the collection by value.
+        TRY(root_element->replace_child(option, *item(index)));
+    }
+
+    return {};
+}
+
 // https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-htmloptionscollection-add
 WebIDL::ExceptionOr<void> HTMLOptionsCollection::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
 {

Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h

@@ -24,6 +24,8 @@ class HTMLOptionsCollection final : public DOM::HTMLCollection {
     [[nodiscard]] static JS::NonnullGCPtr<HTMLOptionsCollection> create(DOM::ParentNode& root, ESCAPING Function<bool(DOM::Element const&)> filter);
     virtual ~HTMLOptionsCollection() override;
 
+    WebIDL::ExceptionOr<void> set_value_of_indexed_property(u32, JS::Value) override;
+
     WebIDL::ExceptionOr<void> set_length(WebIDL::UnsignedLong);
 
     WebIDL::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});