LibWeb: Throw an error on DynamicImport for Worklets or ServiceWorkers

We can't actually create either of these yet, but let's just get this
check out of the way while it is convenient.

Libraries/LibWeb/Bindings/MainThreadVM.cpp

@@ -3,6 +3,7 @@
  * Copyright (c) 2021-2023, Luke Wilde <lukew@serenityos.org>
  * Copyright (c) 2022-2023, networkException <networkexception@serenityos.org>
  * Copyright (c) 2022-2023, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2024, Shannon Booth <shannon@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -45,6 +46,7 @@
 #include <LibWeb/HTML/TagNames.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/HTML/WindowProxy.h>
+#include <LibWeb/HTML/WorkletGlobalScope.h>
 #include <LibWeb/MathML/TagNames.h>
 #include <LibWeb/MediaSourceExtensions/EventNames.h>
 #include <LibWeb/Namespace.h>
@@ -53,6 +55,7 @@
 #include <LibWeb/Platform/EventLoopPlugin.h>
 #include <LibWeb/SVG/AttributeNames.h>
 #include <LibWeb/SVG/TagNames.h>
+#include <LibWeb/ServiceWorker/ServiceWorkerGlobalScope.h>
 #include <LibWeb/UIEvents/EventNames.h>
 #include <LibWeb/UIEvents/InputTypes.h>
 #include <LibWeb/WebGL/EventNames.h>
@@ -435,7 +438,17 @@ ErrorOr<void> initialize_main_thread_vm(HTML::EventLoop::Type type)
         // 1. Let moduleMapRealm be the current realm.
         auto* module_map_realm = vm.current_realm();
 
-        // FIXME: 2. If moduleMapRealm's global object implements WorkletGlobalScope or ServiceWorkerGlobalScope and loadState is undefined, then:
+        // 2. If moduleMapRealm's global object implements WorkletGlobalScope or ServiceWorkerGlobalScope and loadState is undefined, then:
+        if ((is<HTML::WorkletGlobalScope>(module_map_realm->global_object()) || is<ServiceWorker::ServiceWorkerGlobalScope>(module_map_realm->global_object())) && !load_state) {
+            // 1. Let completion be Completion Record { [[Type]]: throw, [[Value]]: a new TypeError, [[Target]]: empty }.
+            auto completion = JS::throw_completion(JS::TypeError::create(*module_map_realm, "Dynamic Import not available for Worklets or ServiceWorkers"_string));
+
+            // 2. Perform FinishLoadingImportedModule(referrer, moduleRequest, payload, completion).
+            JS::finish_loading_imported_module(referrer, module_request, payload, completion);
+
+            // 3. Return.
+            return;
+        }
 
         // 3. Let referencingScript be null.
         Optional<HTML::Script&> referencing_script;