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LibJS: Pre-compute module declaration metadata from AST
Extract the data needed by initialize_environment() from the AST at construction time, following the pattern already used by Script for global declaration instantiation. This pre-computes var declared names, lexical bindings (with function indices), functions to initialize (with SharedFunctionInstanceData), and the default export binding name.
This commit is contained in:
Andreas Kling
Andreas Kling
parent
6082de6487
commit
fa07fd9951
Notes:
github-actions[bot]
2026-02-11 22:59:43 +00:00
Author: https://github.com/awesomekling
Commit: fa07fd9951
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/7896
2 changed files with 85 additions and 63 deletions
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@ -14,6 +14,7 @@
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#include <LibJS/Runtime/GlobalEnvironment.h>
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#include <LibJS/Runtime/ModuleEnvironment.h>
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#include <LibJS/Runtime/PromiseCapability.h>
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#include <LibJS/Runtime/SharedFunctionInstanceData.h>
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#include <LibJS/SourceTextModule.h>
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namespace JS {
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@ -117,6 +118,42 @@ SourceTextModule::SourceTextModule(Realm& realm, StringView filename, Script::Ho
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, m_star_export_entries(move(star_export_entries))
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, m_default_export(move(default_export))
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{
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auto& vm = realm.vm();
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// Pre-compute var declared names (initialize_environment step 21).
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MUST(m_ecmascript_code->for_each_var_declared_identifier([&](Identifier const& identifier) -> ThrowCompletionOr<void> {
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m_var_declared_names.append(identifier.string());
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return {};
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}));
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// Pre-compute lexical bindings and functions to initialize (initialize_environment step 24).
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MUST(m_ecmascript_code->for_each_lexically_scoped_declaration([&](Declaration const& declaration) {
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return declaration.for_each_bound_identifier([&](Identifier const& identifier) -> ThrowCompletionOr<void> {
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LexicalBinding binding;
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binding.name = identifier.string();
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binding.is_constant = declaration.is_constant_declaration();
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if (declaration.is_function_declaration()) {
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VERIFY(is<FunctionDeclaration>(declaration));
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auto const& function_declaration = static_cast<FunctionDeclaration const&>(declaration);
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auto shared_data = function_declaration.ensure_shared_data(vm);
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if (function_declaration.name() == ExportStatement::local_name_for_default)
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shared_data->m_name = "default"_utf16_fly_string;
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binding.function_index = static_cast<i32>(m_functions_to_initialize.size());
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m_functions_to_initialize.append({ *shared_data, shared_data->m_name });
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}
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m_lexical_bindings.append(move(binding));
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return {};
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});
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}));
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// Pre-compute default export binding name (initialize_environment default export block).
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if (m_default_export) {
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VERIFY(m_default_export->has_statement());
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if (!is<Declaration>(m_default_export->statement()))
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m_default_export_binding_name = m_default_export->entries()[0].local_or_import_name.value();
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}
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}
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SourceTextModule::~SourceTextModule() = default;
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@ -126,6 +163,8 @@ void SourceTextModule::visit_edges(Cell::Visitor& visitor)
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Base::visit_edges(visitor);
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visitor.visit(m_import_meta);
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m_execution_context->visit_edges(visitor);
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for (auto const& function : m_functions_to_initialize)
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visitor.visit(function.shared_data);
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}
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// 16.2.1.7.1 ParseModule ( sourceText, realm, hostDefined ), https://tc39.es/ecma262/#sec-parsemodule
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@ -446,18 +485,12 @@ ThrowCompletionOr<void> SourceTextModule::initialize_environment(VM& vm)
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// 18. Let code be module.[[ECMAScriptCode]].
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// 19. Let varDeclarations be the VarScopedDeclarations of code.
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// NOTE: We just loop through them in step 21.
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// 20. Let declaredVarNames be a new empty List.
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Vector<Utf16FlyString> declared_var_names;
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// 21. For each element d of varDeclarations, do
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// a. For each element dn of the BoundNames of d, do
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// NOTE: Due to the use of MUST with `create_mutable_binding` and `initialize_binding` below,
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// an exception should not result from `for_each_var_declared_identifier`.
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MUST(m_ecmascript_code->for_each_var_declared_identifier([&](Identifier const& identifier) {
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auto const& name = identifier.string();
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for (auto const& name : m_var_declared_names) {
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// i. If dn is not an element of declaredVarNames, then
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if (!declared_var_names.contains_slow(name)) {
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// 1. Perform ! env.CreateMutableBinding(dn, false).
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@ -469,72 +502,47 @@ ThrowCompletionOr<void> SourceTextModule::initialize_environment(VM& vm)
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// 3. Append dn to declaredVarNames.
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declared_var_names.empend(name);
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}
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}));
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}
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// 22. Let lexDeclarations be the LexicallyScopedDeclarations of code.
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// NOTE: We only loop through them in step 24.
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// 23. Let privateEnv be null.
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PrivateEnvironment* private_environment = nullptr;
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// 24. For each element d of lexDeclarations, do
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// NOTE: Due to the use of MUST in the callback, an exception should not result from `for_each_lexically_scoped_declaration`.
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MUST(m_ecmascript_code->for_each_lexically_scoped_declaration([&](Declaration const& declaration) {
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for (auto const& binding : m_lexical_bindings) {
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// a. For each element dn of the BoundNames of d, do
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MUST(declaration.for_each_bound_identifier([&](Identifier const& identifier) {
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auto const& name = identifier.string();
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// i. If IsConstantDeclaration of d is true, then
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if (binding.is_constant) {
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// 1. Perform ! env.CreateImmutableBinding(dn, true).
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MUST(environment->create_immutable_binding(vm, binding.name, true));
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}
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// ii. Else,
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else {
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// 1. Perform ! env.CreateMutableBinding(dn, false).
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MUST(environment->create_mutable_binding(vm, binding.name, false));
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}
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// i. If IsConstantDeclaration of d is true, then
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if (declaration.is_constant_declaration()) {
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// 1. Perform ! env.CreateImmutableBinding(dn, true).
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MUST(environment->create_immutable_binding(vm, name, true));
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}
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// ii. Else,
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else {
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// 1. Perform ! env.CreateMutableBinding(dn, false).
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MUST(environment->create_mutable_binding(vm, name, false));
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}
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// iii. If d is a FunctionDeclaration, a GeneratorDeclaration, an AsyncFunctionDeclaration, or an AsyncGeneratorDeclaration, then
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if (binding.function_index >= 0) {
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auto const& function_to_initialize = m_functions_to_initialize[binding.function_index];
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// iii. If d is a FunctionDeclaration, a GeneratorDeclaration, an AsyncFunctionDeclaration, or an AsyncGeneratorDeclaration, then
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if (declaration.is_function_declaration()) {
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VERIFY(is<FunctionDeclaration>(declaration));
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auto const& function_declaration = static_cast<FunctionDeclaration const&>(declaration);
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// 1. Let fo be InstantiateFunctionObject of d with arguments env and privateEnv.
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auto function = ECMAScriptFunctionObject::create_from_function_data(
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realm,
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function_to_initialize.shared_data,
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environment,
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private_environment);
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// 1. Let fo be InstantiateFunctionObject of d with arguments env and privateEnv.
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// NOTE: Special case if the function is a default export of an anonymous function
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// it has name "*default*" but internally should have name "default".
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auto function_name = function_declaration.name();
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if (function_name == ExportStatement::local_name_for_default)
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function_name = "default"_utf16_fly_string;
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auto function = ECMAScriptFunctionObject::create_from_function_node(
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function_declaration,
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move(function_name),
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realm,
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environment,
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private_environment);
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// 2. Perform ! env.InitializeBinding(dn, fo, normal).
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MUST(environment->initialize_binding(vm, name, function, Environment::InitializeBindingHint::Normal));
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}
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}));
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}));
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// 2. Perform ! env.InitializeBinding(dn, fo, normal).
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MUST(environment->initialize_binding(vm, binding.name, function, Environment::InitializeBindingHint::Normal));
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}
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}
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// NOTE: The default export name is also part of the local lexical declarations but instead of making that a special
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// case in the parser we just check it here. This is only needed for things which are not declarations. For more
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// info check Parser::parse_export_statement. Furthermore, that declaration is not constant. so we take 24.a.ii.
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if (m_default_export) {
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VERIFY(m_default_export->has_statement());
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if (auto const& statement = m_default_export->statement(); !is<Declaration>(statement)) {
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auto const& name = m_default_export->entries()[0].local_or_import_name.value();
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dbgln_if(JS_MODULE_DEBUG, "[JS MODULE] Adding default export to lexical declarations: local name: {}, Expression: {}", name, statement.class_name());
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// 1. Perform ! env.CreateMutableBinding(dn, false).
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MUST(environment->create_mutable_binding(vm, name, false));
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// NOTE: Since this is not a function declaration 24.a.iii never applies
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}
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}
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if (m_default_export_binding_name.has_value())
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MUST(environment->create_mutable_binding(vm, *m_default_export_binding_name, false));
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// 25. Remove moduleContext from the execution context stack.
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vm.pop_execution_context();
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