LibWeb: Use correct integer parsing rules in HTMLLIElement::value()

(cherry picked from commit a61883ae88eb3fd4b35cc51db77a4c9405480fb5)

Userland/Libraries/LibWeb/HTML/HTMLLIElement.cpp

@@ -6,6 +6,7 @@
 
 #include <LibWeb/Bindings/HTMLLIElementPrototype.h>
 #include <LibWeb/HTML/HTMLLIElement.h>
+#include <LibWeb/HTML/Numbers.h>
 #include <LibWeb/HTML/Window.h>
 
 namespace Web::HTML {
@@ -25,4 +26,16 @@ void HTMLLIElement::initialize(JS::Realm& realm)
     WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLLIElement);
 }
 
+// https://html.spec.whatwg.org/multipage/grouping-content.html#dom-li-value
+WebIDL::Long HTMLLIElement::value()
+{
+    // The value IDL attribute must reflect the value of the value content attribute.
+    // NOTE: This is equivalent to the code that would be generated by the IDL generator if we used [Reflect] on the value attribute.
+    //       We don't do that in this case, since this method is used elsewhere.
+    auto content_attribute_value = get_attribute(AttributeNames::value).value_or("0"_string);
+    if (auto maybe_number = HTML::parse_integer(content_attribute_value); maybe_number.has_value())
+        return *maybe_number;
+    return 0;
+}
+
 }

Userland/Libraries/LibWeb/HTML/HTMLLIElement.h

@@ -8,6 +8,7 @@
 
 #include <LibWeb/ARIA/Roles.h>
 #include <LibWeb/HTML/HTMLElement.h>
+#include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
@@ -21,8 +22,8 @@ class HTMLLIElement final : public HTMLElement {
     // https://www.w3.org/TR/html-aria/#el-li
     virtual Optional<ARIA::Role> default_role() const override { return ARIA::Role::listitem; }
 
-    i32 value() { return get_attribute(AttributeNames::value).value_or("0"_string).to_number<i32>().value_or(0); }
-    void set_value(i32 value)
+    WebIDL::Long value();
+    void set_value(WebIDL::Long value)
     {
         set_attribute(AttributeNames::value, MUST(String::number(value))).release_value_but_fixme_should_propagate_errors();
     }