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ladybird/Userland/Libraries/LibJS/Runtime/VM.cpp
Andreas Kling bce7fdba81 LibJS: Bring Reference records a bit closer to the ECMAScript spec 
Our Reference class now has the same fields as the spec:

- Base (a non-nullish value, an environment record, or `unresolvable`)
- Referenced Name (the name of the binding)
- Strict (whether the reference originated in strict mode code)
- ThisValue (if non-empty, the reference represents a `super` keyword)

The main difference from before is that we now resolve the environment
record that a reference interacts with. Previously we simply resolved
to either "local variable" or "global variable".

The associated abstract operations are still largely non-conforming,
since we don't yet implement proper variable bindings. But this patch
should at least fix a handful of test262 cases. :^)

There's one minor regression: some TypeError message strings get
a little worse due to doing a RequireObjectCoercible earlier in the
evaluation of MemberExpression.
2021-06-25 16:58:36 +02:00

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/*
* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Debug.h>
#include <AK/ScopeGuard.h>
#include <AK/StringBuilder.h>
#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/FinalizationRegistry.h>
#include <LibJS/Runtime/FunctionEnvironmentRecord.h>
#include <LibJS/Runtime/GlobalEnvironmentRecord.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/IteratorOperations.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/PromiseReaction.h>
#include <LibJS/Runtime/Reference.h>
#include <LibJS/Runtime/ScriptFunction.h>
#include <LibJS/Runtime/Symbol.h>
#include <LibJS/Runtime/TemporaryClearException.h>
#include <LibJS/Runtime/VM.h>
namespace JS {
NonnullRefPtr<VM> VM::create()
{
return adopt_ref(*new VM);
}
VM::VM()
: m_heap(*this)
{
m_empty_string = m_heap.allocate_without_global_object<PrimitiveString>(String::empty());
for (size_t i = 0; i < 128; ++i) {
m_single_ascii_character_strings[i] = m_heap.allocate_without_global_object<PrimitiveString>(String::formatted("{:c}", i));
}
#define __JS_ENUMERATE(SymbolName, snake_name) \
m_well_known_symbol_##snake_name = js_symbol(*this, "Symbol." #SymbolName, false);
JS_ENUMERATE_WELL_KNOWN_SYMBOLS
#undef __JS_ENUMERATE
}
VM::~VM()
{
}
Interpreter& VM::interpreter()
{
VERIFY(!m_interpreters.is_empty());
return *m_interpreters.last();
}
Interpreter* VM::interpreter_if_exists()
{
if (m_interpreters.is_empty())
return nullptr;
return m_interpreters.last();
}
void VM::push_interpreter(Interpreter& interpreter)
{
m_interpreters.append(&interpreter);
}
void VM::pop_interpreter(Interpreter& interpreter)
{
VERIFY(!m_interpreters.is_empty());
auto* popped_interpreter = m_interpreters.take_last();
VERIFY(popped_interpreter == &interpreter);
}
VM::InterpreterExecutionScope::InterpreterExecutionScope(Interpreter& interpreter)
: m_interpreter(interpreter)
{
m_interpreter.vm().push_interpreter(m_interpreter);
}
VM::InterpreterExecutionScope::~InterpreterExecutionScope()
{
m_interpreter.vm().pop_interpreter(m_interpreter);
}
void VM::gather_roots(HashTable<Cell*>& roots)
{
roots.set(m_empty_string);
for (auto* string : m_single_ascii_character_strings)
roots.set(string);
roots.set(m_exception);
if (m_last_value.is_cell())
roots.set(&m_last_value.as_cell());
for (auto& execution_context : m_execution_context_stack) {
if (execution_context->this_value.is_cell())
roots.set(&execution_context->this_value.as_cell());
roots.set(execution_context->arguments_object);
for (auto& argument : execution_context->arguments) {
if (argument.is_cell())
roots.set(&argument.as_cell());
}
roots.set(execution_context->lexical_environment);
roots.set(execution_context->variable_environment);
}
#define __JS_ENUMERATE(SymbolName, snake_name) \
roots.set(well_known_symbol_##snake_name());
JS_ENUMERATE_WELL_KNOWN_SYMBOLS
#undef __JS_ENUMERATE
for (auto& symbol : m_global_symbol_map)
roots.set(symbol.value);
for (auto* job : m_promise_jobs)
roots.set(job);
}
Symbol* VM::get_global_symbol(const String& description)
{
auto result = m_global_symbol_map.get(description);
if (result.has_value())
return result.value();
auto new_global_symbol = js_symbol(*this, description, true);
m_global_symbol_map.set(description, new_global_symbol);
return new_global_symbol;
}
void VM::set_variable(const FlyString& name, Value value, GlobalObject& global_object, bool first_assignment, EnvironmentRecord* specific_scope)
{
Optional<Variable> possible_match;
if (!specific_scope && m_execution_context_stack.size()) {
for (auto* environment_record = lexical_environment(); environment_record; environment_record = environment_record->outer_environment()) {
possible_match = environment_record->get_from_environment_record(name);
if (possible_match.has_value()) {
specific_scope = environment_record;
break;
}
}
}
if (specific_scope && possible_match.has_value()) {
if (!first_assignment && possible_match.value().declaration_kind == DeclarationKind::Const) {
throw_exception<TypeError>(global_object, ErrorType::InvalidAssignToConst);
return;
}
specific_scope->put_into_environment_record(name, { value, possible_match.value().declaration_kind });
return;
}
if (specific_scope) {
specific_scope->put_into_environment_record(name, { value, DeclarationKind::Var });
return;
}
global_object.put(name, value);
}
bool VM::delete_variable(FlyString const& name)
{
EnvironmentRecord* specific_scope = nullptr;
Optional<Variable> possible_match;
if (!m_execution_context_stack.is_empty()) {
for (auto* environment_record = lexical_environment(); environment_record; environment_record = environment_record->outer_environment()) {
possible_match = environment_record->get_from_environment_record(name);
if (possible_match.has_value()) {
specific_scope = environment_record;
break;
}
}
}
if (!possible_match.has_value())
return false;
if (possible_match.value().declaration_kind == DeclarationKind::Const)
return false;
VERIFY(specific_scope);
return specific_scope->delete_from_environment_record(name);
}
void VM::assign(const FlyString& target, Value value, GlobalObject& global_object, bool first_assignment, EnvironmentRecord* specific_scope)
{
set_variable(target, move(value), global_object, first_assignment, specific_scope);
}
void VM::assign(const Variant<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>& target, Value value, GlobalObject& global_object, bool first_assignment, EnvironmentRecord* specific_scope)
{
if (auto id_ptr = target.get_pointer<NonnullRefPtr<Identifier>>())
return assign((*id_ptr)->string(), move(value), global_object, first_assignment, specific_scope);
assign(target.get<NonnullRefPtr<BindingPattern>>(), move(value), global_object, first_assignment, specific_scope);
}
void VM::assign(const NonnullRefPtr<BindingPattern>& target, Value value, GlobalObject& global_object, bool first_assignment, EnvironmentRecord* specific_scope)
{
auto& binding = *target;
switch (binding.kind) {
case BindingPattern::Kind::Array: {
auto iterator = get_iterator(global_object, value);
if (!iterator)
return;
for (size_t i = 0; i < binding.entries.size(); i++) {
if (exception())
return;
auto& entry = binding.entries[i];
if (entry.is_rest) {
VERIFY(i == binding.entries.size() - 1);
auto* array = Array::create(global_object);
for (;;) {
auto next_object = iterator_next(*iterator);
if (!next_object)
return;
auto done_property = next_object->get(names.done);
if (exception())
return;
if (!done_property.is_empty() && done_property.to_boolean())
break;
auto next_value = next_object->get(names.value);
if (exception())
return;
array->indexed_properties().append(next_value);
}
value = array;
} else if (iterator) {
auto next_object = iterator_next(*iterator);
if (!next_object)
return;
auto done_property = next_object->get(names.done);
if (exception())
return;
if (!done_property.is_empty() && done_property.to_boolean()) {
iterator = nullptr;
value = js_undefined();
} else {
value = next_object->get(names.value);
if (exception())
return;
}
} else {
value = js_undefined();
}
if (value.is_undefined() && entry.initializer) {
value = entry.initializer->execute(interpreter(), global_object);
if (exception())
return;
}
entry.alias.visit(
[&](Empty) {},
[&](NonnullRefPtr<Identifier> const& identifier) {
set_variable(identifier->string(), value, global_object, first_assignment, specific_scope);
},
[&](NonnullRefPtr<BindingPattern> const& pattern) {
assign(pattern, value, global_object, first_assignment, specific_scope);
});
if (entry.is_rest)
break;
}
break;
}
case BindingPattern::Kind::Object: {
auto object = value.to_object(global_object);
HashTable<PropertyName, PropertyNameTraits> seen_names;
for (auto& property : binding.entries) {
VERIFY(!property.is_elision());
PropertyName assignment_name;
JS::Value value_to_assign;
if (property.is_rest) {
VERIFY(property.name.has<NonnullRefPtr<Identifier>>());
assignment_name = property.name.get<NonnullRefPtr<Identifier>>()->string();
auto* rest_object = Object::create(global_object, global_object.object_prototype());
for (auto& object_property : object->shape().property_table()) {
if (!object_property.value.attributes.has_enumerable())
continue;
if (seen_names.contains(object_property.key.to_display_string()))
continue;
rest_object->put(object_property.key, object->get(object_property.key));
if (exception())
return;
}
value_to_assign = rest_object;
} else {
property.name.visit(
[&](Empty) { VERIFY_NOT_REACHED(); },
[&](NonnullRefPtr<Identifier> const& identifier) {
assignment_name = identifier->string();
},
[&](NonnullRefPtr<Expression> const& expression) {
auto result = expression->execute(interpreter(), global_object);
if (exception())
return;
assignment_name = result.to_property_key(global_object);
});
if (exception())
break;
value_to_assign = object->get(assignment_name);
}
seen_names.set(assignment_name);
if (value_to_assign.is_empty())
value_to_assign = js_undefined();
if (value_to_assign.is_undefined() && property.initializer)
value_to_assign = property.initializer->execute(interpreter(), global_object);
if (exception())
break;
property.alias.visit(
[&](Empty) {
set_variable(assignment_name.to_string(), value_to_assign, global_object, first_assignment, specific_scope);
},
[&](NonnullRefPtr<Identifier> const& identifier) {
VERIFY(!property.is_rest);
set_variable(identifier->string(), value_to_assign, global_object, first_assignment, specific_scope);
},
[&](NonnullRefPtr<BindingPattern> const& pattern) {
VERIFY(!property.is_rest);
assign(pattern, value_to_assign, global_object, first_assignment, specific_scope);
});
if (property.is_rest)
break;
}
break;
}
}
}
Value VM::get_variable(const FlyString& name, GlobalObject& global_object)
{
if (!m_execution_context_stack.is_empty()) {
auto& context = running_execution_context();
if (name == names.arguments.as_string() && context.function) {
// HACK: Special handling for the name "arguments":
// If the name "arguments" is defined in the current scope, for example via
// a function parameter, or by a local var declaration, we use that.
// Otherwise, we return a lazily constructed Array with all the argument values.
// FIXME: Do something much more spec-compliant.
auto possible_match = lexical_environment()->get_from_environment_record(name);
if (possible_match.has_value())
return possible_match.value().value;
if (!context.arguments_object) {
context.arguments_object = Array::create(global_object);
context.arguments_object->put(names.callee, context.function);
for (auto argument : context.arguments) {
context.arguments_object->indexed_properties().append(argument);
}
}
return context.arguments_object;
}
for (auto* environment_record = lexical_environment(); environment_record; environment_record = environment_record->outer_environment()) {
auto possible_match = environment_record->get_from_environment_record(name);
if (exception())
return {};
if (possible_match.has_value())
return possible_match.value().value;
}
}
auto value = global_object.get(name);
if (m_underscore_is_last_value && name == "_" && value.is_empty())
return m_last_value;
return value;
}
// 9.4.2 ResolveBinding ( name [ , env ] ), https://tc39.es/ecma262/#sec-resolvebinding
Reference VM::resolve_binding(GlobalObject& global_object, FlyString const& name, EnvironmentRecord*)
{
// FIXME: This implementation of ResolveBinding is non-conforming.
for (auto* environment_record = lexical_environment(); environment_record && environment_record->outer_environment(); environment_record = environment_record->outer_environment()) {
auto possible_match = environment_record->get_from_environment_record(name);
if (possible_match.has_value())
return Reference { *environment_record, name };
}
return Reference { global_object.environment_record(), name };
}
Value VM::construct(Function& function, Function& new_target, Optional<MarkedValueList> arguments)
{
auto& global_object = function.global_object();
ExecutionContext execution_context;
execution_context.function = &function;
if (auto* interpreter = interpreter_if_exists())
execution_context.current_node = interpreter->current_node();
execution_context.is_strict_mode = function.is_strict_mode();
push_execution_context(execution_context, global_object);
if (exception())
return {};
ArmedScopeGuard pop_guard = [&] {
pop_execution_context();
};
execution_context.function_name = function.name();
execution_context.arguments = function.bound_arguments();
if (arguments.has_value())
execution_context.arguments.extend(arguments.value().values());
auto* environment = function.create_environment_record();
execution_context.lexical_environment = environment;
execution_context.variable_environment = environment;
if (environment)
environment->set_new_target(&new_target);
Object* new_object = nullptr;
if (function.constructor_kind() == Function::ConstructorKind::Base) {
new_object = Object::create(global_object, nullptr);
if (environment)
environment->bind_this_value(global_object, new_object);
if (exception())
return {};
auto prototype = new_target.get(names.prototype);
if (exception())
return {};
if (prototype.is_object()) {
new_object->set_prototype(&prototype.as_object());
if (exception())
return {};
}
}
// If we are a Derived constructor, |this| has not been constructed before super is called.
Value this_value = function.constructor_kind() == Function::ConstructorKind::Base ? new_object : Value {};
execution_context.this_value = this_value;
auto result = function.construct(new_target);
if (environment)
this_value = environment->get_this_binding(global_object);
pop_execution_context();
pop_guard.disarm();
// If we are constructing an instance of a derived class,
// set the prototype on objects created by constructors that return an object (i.e. NativeFunction subclasses).
if (function.constructor_kind() == Function::ConstructorKind::Base && new_target.constructor_kind() == Function::ConstructorKind::Derived && result.is_object()) {
if (environment) {
verify_cast<FunctionEnvironmentRecord>(lexical_environment())->replace_this_binding(result);
}
auto prototype = new_target.get(names.prototype);
if (exception())
return {};
if (prototype.is_object()) {
result.as_object().set_prototype(&prototype.as_object());
if (exception())
return {};
}
return result;
}
if (exception())
return {};
if (result.is_object())
return result;
return this_value;
}
void VM::throw_exception(Exception& exception)
{
set_exception(exception);
unwind(ScopeType::Try);
}
// 9.4.4 ResolveThisBinding ( ), https://tc39.es/ecma262/#sec-resolvethisbinding
Value VM::resolve_this_binding(GlobalObject& global_object)
{
auto& environment = get_this_environment(*this);
return environment.get_this_binding(global_object);
}
String VM::join_arguments(size_t start_index) const
{
StringBuilder joined_arguments;
for (size_t i = start_index; i < argument_count(); ++i) {
joined_arguments.append(argument(i).to_string_without_side_effects().characters());
if (i != argument_count() - 1)
joined_arguments.append(' ');
}
return joined_arguments.build();
}
Value VM::get_new_target()
{
auto& env = get_this_environment(*this);
return verify_cast<FunctionEnvironmentRecord>(env).new_target();
}
Value VM::call_internal(Function& function, Value this_value, Optional<MarkedValueList> arguments)
{
VERIFY(!exception());
VERIFY(!this_value.is_empty());
ExecutionContext execution_context;
execution_context.function = &function;
if (auto* interpreter = interpreter_if_exists())
execution_context.current_node = interpreter->current_node();
execution_context.is_strict_mode = function.is_strict_mode();
execution_context.function_name = function.name();
execution_context.this_value = function.bound_this().value_or(this_value);
execution_context.arguments = function.bound_arguments();
if (arguments.has_value())
execution_context.arguments.extend(arguments.value().values());
auto* environment = function.create_environment_record();
execution_context.lexical_environment = environment;
execution_context.variable_environment = environment;
if (environment) {
VERIFY(environment->this_binding_status() == FunctionEnvironmentRecord::ThisBindingStatus::Uninitialized);
environment->bind_this_value(function.global_object(), execution_context.this_value);
}
if (exception())
return {};
push_execution_context(execution_context, function.global_object());
if (exception())
return {};
auto result = function.call();
pop_execution_context();
return result;
}
bool VM::in_strict_mode() const
{
if (execution_context_stack().is_empty())
return false;
return running_execution_context().is_strict_mode;
}
void VM::run_queued_promise_jobs()
{
dbgln_if(PROMISE_DEBUG, "Running queued promise jobs");
// Temporarily get rid of the exception, if any - job functions must be called
// either way, and that can't happen if we already have an exception stored.
TemporaryClearException clear_exception(*this);
while (!m_promise_jobs.is_empty()) {
auto* job = m_promise_jobs.take_first();
dbgln_if(PROMISE_DEBUG, "Calling promise job function @ {}", job);
[[maybe_unused]] auto result = call(*job, js_undefined());
}
// Ensure no job has created a new exception, they must clean up after themselves.
VERIFY(!m_exception);
}
// 9.5.4 HostEnqueuePromiseJob ( job, realm ), https://tc39.es/ecma262/#sec-hostenqueuepromisejob
void VM::enqueue_promise_job(NativeFunction& job)
{
m_promise_jobs.append(&job);
}
void VM::run_queued_finalization_registry_cleanup_jobs()
{
while (!m_finalization_registry_cleanup_jobs.is_empty()) {
auto* registry = m_finalization_registry_cleanup_jobs.take_first();
registry->cleanup();
}
}
// 9.10.4.1 HostEnqueueFinalizationRegistryCleanupJob ( finalizationRegistry ), https://tc39.es/ecma262/#sec-host-cleanup-finalization-registry
void VM::enqueue_finalization_registry_cleanup_job(FinalizationRegistry& registry)
{
m_finalization_registry_cleanup_jobs.append(&registry);
}
// 27.2.1.9 HostPromiseRejectionTracker ( promise, operation ), https://tc39.es/ecma262/#sec-host-promise-rejection-tracker
void VM::promise_rejection_tracker(const Promise& promise, Promise::RejectionOperation operation) const
{
switch (operation) {
case Promise::RejectionOperation::Reject:
// A promise was rejected without any handlers
if (on_promise_unhandled_rejection)
on_promise_unhandled_rejection(promise);
break;
case Promise::RejectionOperation::Handle:
// A handler was added to an already rejected promise
if (on_promise_rejection_handled)
on_promise_rejection_handled(promise);
break;
default:
VERIFY_NOT_REACHED();
}
}
void VM::dump_backtrace() const
{
for (ssize_t i = m_execution_context_stack.size() - 1; i >= 0; --i)
dbgln("-> {}", m_execution_context_stack[i]->function_name);
}
void VM::dump_environment_record_chain() const
{
for (auto* environment_record = lexical_environment(); environment_record; environment_record = environment_record->outer_environment()) {
dbgln("+> {} ({:p})", environment_record->class_name(), environment_record);
if (is<DeclarativeEnvironmentRecord>(*environment_record)) {
auto& declarative_environment_record = static_cast<DeclarativeEnvironmentRecord const&>(*environment_record);
for (auto& variable : declarative_environment_record.variables()) {
dbgln(" {}", variable.key);
}
}
}
}
}
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