LibWeb: Support "importmap" scripts

Author: https://github.com/jamierocks
Commit: e487f70bbf
Pull-request: https://github.com/SerenityOS/serenity/pull/23954
Issue: https://github.com/SerenityOS/serenity/issues/23117

Userland/Libraries/LibWeb/HTML/Scripting/ImportMapParseResult.cpp

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/ModuleRequest.h>
+#include <LibWeb/HTML/Scripting/ExceptionReporter.h>
+#include <LibWeb/HTML/Scripting/ImportMapParseResult.h>
+#include <LibWeb/HTML/Window.h>
+#include <LibWeb/WebIDL/DOMException.h>
+
+namespace Web::HTML {
+
+JS_DEFINE_ALLOCATOR(ImportMapParseResult);
+
+ImportMapParseResult::ImportMapParseResult() = default;
+
+ImportMapParseResult::~ImportMapParseResult() = default;
+
+// https://html.spec.whatwg.org/multipage/webappapis.html#create-an-import-map-parse-result
+JS::NonnullGCPtr<ImportMapParseResult> ImportMapParseResult::create(JS::Realm& realm, ByteString const& input, URL::URL base_url)
+{
+    // 1. Let result be an import map parse result whose import map is null and whose error to rethrow is null.
+    auto result = realm.heap().allocate<ImportMapParseResult>(realm);
+    result->set_error_to_rethrow(JS::js_null());
+
+    // 2. Parse an import map string given input and baseURL, catching any exceptions.
+    auto import_map = parse_import_map_string(realm, input, base_url);
+
+    // 2.1. If this threw an exception, then set result's error to rethrow to that exception.
+    // FIXME: rethrow the original exception
+    if (import_map.is_exception())
+        result->set_error_to_rethrow(JS::Error::create(realm, "Failed to parse import map string"sv));
+
+    // 2.2. Otherwise, set result's import map to the return value.
+    else
+        result->set_import_map(import_map.release_value());
+
+    // 3. Return result.
+    return result;
+}
+
+void ImportMapParseResult::visit_host_defined_self(JS::Cell::Visitor& visitor)
+{
+    visitor.visit(*this);
+}
+
+void ImportMapParseResult::visit_edges(Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_error_to_rethrow);
+}
+
+// https://html.spec.whatwg.org/multipage/webappapis.html#register-an-import-map
+void ImportMapParseResult::register_import_map(Window& global)
+{
+    // 1. If result's error to rethrow is not null, then report the exception given by result's error to rethrow and return.
+    if (!m_error_to_rethrow.is_null()) {
+        HTML::report_exception(m_error_to_rethrow, global.realm());
+        return;
+    }
+
+    // 2. Assert: global's import map is an empty import map.
+    VERIFY(global.import_map().imports().is_empty() && global.import_map().scopes().is_empty());
+
+    // 3. Set global's import map to result's import map.
+    VERIFY(m_import_map.has_value());
+    global.set_import_map(m_import_map.value());
+}
+
+}