LibWeb: Implement ModuleScript and JavaScriptModuleScript

This patchs adds the Web::HTML::Script subclass ModuleScript and
JavaScriptModuleScript as a type of ModuleScript as well as various
algorithms related to JavaScript module scripts.

Co-authored-by: davidot <davidot@serenityos.org>

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

@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2022, networkException <networkexception@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Interpreter.h>
+#include <LibWeb/HTML/Scripting/Environments.h>
+#include <LibWeb/HTML/Scripting/Fetching.h>
+#include <LibWeb/HTML/Scripting/ModuleScript.h>
+#include <LibWeb/WebIDL/DOMException.h>
+
+namespace Web::HTML {
+
+ModuleScript::~ModuleScript() = default;
+
+ModuleScript::ModuleScript(AK::URL base_url, String filename, EnvironmentSettingsObject& environment_settings_object)
+    : Script(move(base_url), move(filename), environment_settings_object)
+{
+}
+
+JavaScriptModuleScript::~JavaScriptModuleScript() = default;
+
+JavaScriptModuleScript::JavaScriptModuleScript(AK::URL base_url, String filename, EnvironmentSettingsObject& environment_settings_object)
+    : ModuleScript(move(base_url), move(filename), environment_settings_object)
+{
+}
+
+// https://html.spec.whatwg.org/multipage/webappapis.html#creating-a-javascript-module-script
+JS::GCPtr<JavaScriptModuleScript> JavaScriptModuleScript::create(String const& filename, StringView source, EnvironmentSettingsObject& settings_object, AK::URL base_url)
+{
+    // 1. If scripting is disabled for settings, then set source to the empty string.
+    if (settings_object.is_scripting_disabled())
+        source = ""sv;
+
+    auto& realm = settings_object.realm();
+
+    // 2. Let script be a new module script that this algorithm will subsequently initialize.
+    auto* script = realm.heap().allocate<JavaScriptModuleScript>(realm, move(base_url), filename, settings_object);
+
+    // 3. Set script's settings object to settings. (NOTE: This was already done when constructing.)
+
+    // 4. Set script's base URL to baseURL. (NOTE: This was already done when constructing.)
+
+    // FIXME: 5. Set script's fetch options to options.
+
+    // 6. Set script's parse error and error to rethrow to null.
+    // NOTE: Parse error and error to rethrow were set to null in the construction of Script.
+
+    // 7. Let result be ParseModule(source, settings's Realm, script).
+    auto result = JS::SourceTextModule::parse(source, settings_object.realm(), filename.view(), script);
+
+    // 8. If result is a list of errors, then:
+    if (result.is_error()) {
+        auto& parse_error = result.error().first();
+        dbgln("JavaScriptModuleScript: Failed to parse: {}", parse_error.to_string());
+
+        // FIXME: 1. Set script's parse error to result[0].
+
+        // 2. Return script.
+        return script;
+    }
+
+    // 10. For each ModuleRequest record requested of result.[[RequestedModules]]:
+    for (auto const& requested : result.value()->requested_modules()) {
+        // FIXME: Clarify if this should be checked for all requested before running the steps below.
+        // 9. Assert: requested.[[Assertions]] does not contain any Record entry such that entry.[[Key]] is not "type",
+        //            because we only asked for "type" assertions in HostGetSupportedImportAssertions.
+        VERIFY(all_of(requested.assertions, [](auto const& assertion) { return assertion.key == "type"sv; }));
+
+        // 1. Let url be the result of resolving a module specifier given script's base URL and requested.[[Specifier]].
+        auto url = resolve_module_specifier(requested, script->base_url());
+
+        // 2. Let moduleType be the result of running the module type from module request steps given requested.
+        auto module_type = module_type_from_module_request(requested);
+
+        // 3. If url is failure, or if the result of running the module type allowed steps given moduleType and settings is false, then:
+        if (!url.is_valid() || !settings_object.module_type_allowed(module_type)) {
+            // FIXME: 1. Let error be a new TypeError exception.
+
+            // FIXME: 2. Set script's parse error to error.
+
+            // FIXME: 3. Return script.
+            TODO();
+        }
+    }
+
+    // 11. Set script's record to result.
+    script->m_record = result.value();
+
+    // 12. Return script.
+    return script;
+}
+
+// https://html.spec.whatwg.org/multipage/webappapis.html#run-a-module-script
+JS::Promise* JavaScriptModuleScript::run(PreventErrorReporting)
+{
+    // 1. Let settings be the settings object of script.
+    auto& settings = settings_object();
+
+    // 2. Check if we can run script with settings. If this returns "do not run", then return a promise resolved with undefined.
+    if (settings.can_run_script() == RunScriptDecision::DoNotRun) {
+        auto* promise = JS::Promise::create(settings.realm());
+        promise->fulfill(JS::js_undefined());
+        return promise;
+    }
+
+    // 3. Prepare to run script given settings.
+    settings.prepare_to_run_script();
+
+    // 4. Let evaluationPromise be null.
+    JS::Promise* evaluation_promise = nullptr;
+
+    // FIXME: 5. If script's error to rethrow is not null, then set evaluationPromise to a promise rejected with script's error to rethrow.
+
+    // 6. Otherwise:
+    if (m_record) {
+        // 1. Let record be script's record.
+        auto record = m_record;
+
+        auto interpreter = JS::Interpreter::create_with_existing_realm(settings.realm());
+        JS::VM::InterpreterExecutionScope scope(*interpreter);
+
+        // 2. Set evaluationPromise to record.Evaluate().
+        auto elevation_promise_or_error = record->evaluate(vm());
+
+        // NOTE: This step will recursively evaluate all of the module's dependencies.
+        // If Evaluate fails to complete as a result of the user agent aborting the running script,
+        // then set evaluationPromise to a promise rejected with a new "QuotaExceededError" DOMException.
+        if (elevation_promise_or_error.is_error()) {
+            auto* promise = JS::Promise::create(settings_object().realm());
+            promise->reject(WebIDL::QuotaExceededError::create(settings_object().realm(), "Failed to evaluate module script").ptr());
+
+            evaluation_promise = promise;
+        } else {
+            evaluation_promise = elevation_promise_or_error.value();
+        }
+    } else {
+        TODO();
+    }
+
+    // FIXME: 7. If preventErrorReporting is false, then upon rejection of evaluationPromise with reason, report the exception given by reason for script.
+
+    // 8. Clean up after running script with settings.
+    settings.clean_up_after_running_script();
+
+    // 9. Return evaluationPromise.
+    return evaluation_promise;
+}
+
+void JavaScriptModuleScript::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_record);
+}
+
+}