LibWeb/CSS: Stub out StylePropertyMapReadOnly

Nothing yet produces this, and the useful parts of get() and get_all()
will have to wait until type reification is implemented.

Libraries/LibWeb/CSS/StylePropertyMapReadOnly.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "StylePropertyMapReadOnly.h"
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/Bindings/StylePropertyMapReadOnlyPrototype.h>
+#include <LibWeb/CSS/CSSStyleDeclaration.h>
+#include <LibWeb/CSS/PropertyName.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+
+namespace Web::CSS {
+
+GC_DEFINE_ALLOCATOR(StylePropertyMapReadOnly);
+
+GC::Ref<StylePropertyMapReadOnly> StylePropertyMapReadOnly::create_computed_style(JS::Realm& realm, DOM::AbstractElement element)
+{
+    return realm.create<StylePropertyMapReadOnly>(realm, element);
+}
+
+StylePropertyMapReadOnly::StylePropertyMapReadOnly(JS::Realm& realm, Optional<DOM::AbstractElement> element)
+    : Bindings::PlatformObject(realm)
+    , m_source_element(move(element))
+{
+}
+
+StylePropertyMapReadOnly::StylePropertyMapReadOnly(JS::Realm& realm, GC::Ref<CSSStyleDeclaration> declaration)
+    : Bindings::PlatformObject(realm)
+    , m_source_declaration(declaration)
+{
+}
+
+StylePropertyMapReadOnly::~StylePropertyMapReadOnly() = default;
+
+void StylePropertyMapReadOnly::initialize(JS::Realm& realm)
+{
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(StylePropertyMapReadOnly);
+    Base::initialize(realm);
+}
+
+void StylePropertyMapReadOnly::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+
+    visitor.visit(m_source_declaration);
+    if (m_source_element.has_value())
+        m_source_element->visit(visitor);
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-stylepropertymapreadonly-get
+WebIDL::ExceptionOr<Variant<GC::Ref<CSSStyleValue>, Empty>> StylePropertyMapReadOnly::get(String property)
+{
+    // The get(property) method, when called on a StylePropertyMapReadOnly this, must perform the following steps:
+
+    // 1. If property is not a custom property name string, set property to property ASCII lowercased.
+    if (!is_a_custom_property_name_string(property))
+        property = property.to_ascii_lowercase();
+
+    // 2. If property is not a valid CSS property, throw a TypeError.
+    if (!is_a_valid_css_property(property))
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("'{}' is not a valid CSS property", property)) };
+
+    // 3. Let props be the value of this’s [[declarations]] internal slot.
+    auto& props = m_declarations;
+
+    // FIXME: 4. If props[property] exists, subdivide into iterations props[property], then reify the first item of the result and return it.
+    (void)props;
+
+    // 5. Otherwise, return undefined.
+    return Empty {};
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-stylepropertymapreadonly-getall
+WebIDL::ExceptionOr<Vector<GC::Ref<CSSStyleValue>>> StylePropertyMapReadOnly::get_all(String property)
+{
+    // The getAll(property) method, when called on a StylePropertyMap this, must perform the following steps:
+
+    // 1. If property is not a custom property name string, set property to property ASCII lowercased.
+    if (!is_a_custom_property_name_string(property))
+        property = property.to_ascii_lowercase();
+
+    // 2. If property is not a valid CSS property, throw a TypeError.
+    if (!is_a_valid_css_property(property))
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("'{}' is not a valid CSS property", property)) };
+
+    // 3. Let props be the value of this’s [[declarations]] internal slot.
+    auto& props = m_declarations;
+
+    // FIXME: 4. If props[property] exists, subdivide into iterations props[property], then reify each item of the result, and return the list.
+    (void)props;
+
+    // 5. Otherwise, return an empty list.
+    return Vector<GC::Ref<CSSStyleValue>> {};
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-stylepropertymapreadonly-has
+WebIDL::ExceptionOr<bool> StylePropertyMapReadOnly::has(String property)
+{
+    // The has(property) method, when called on a StylePropertyMapReadOnly this, must perform the following steps:
+
+    // 1. If property is not a custom property name string, set property to property ASCII lowercased.
+    if (!is_a_custom_property_name_string(property))
+        property = property.to_ascii_lowercase();
+
+    // 2. If property is not a valid CSS property, throw a TypeError.
+    if (!is_a_valid_css_property(property))
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("'{}' is not a valid CSS property", property)) };
+
+    // 3. Let props be the value of this’s [[declarations]] internal slot.
+    auto& props = m_declarations;
+
+    // 4. If props[property] exists, return true. Otherwise, return false.
+    return props.contains(property);
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-stylepropertymapreadonly-size
+WebIDL::UnsignedLong StylePropertyMapReadOnly::size() const
+{
+    // The size attribute, on getting from a StylePropertyMapReadOnly this, must perform the following steps:
+
+    // 1. Return the size of the value of this’s [[declarations]] internal slot.
+    return m_declarations.size();
+}
+
+}