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ladybird/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp

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/*
* Copyright (c) 2020, Stephan Unverwerth <s.unverwerth@serenityos.org>
* Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Debug.h>
#include <AK/Function.h>
#include <LibJS/AST.h>
#include <LibJS/Bytecode/BasicBlock.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Interpreter.h>
#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/AsyncFunctionDriverWrapper.h>
#include <LibJS/Runtime/ECMAScriptFunctionObject.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/ExecutionContext.h>
#include <LibJS/Runtime/FunctionEnvironment.h>
#include <LibJS/Runtime/GeneratorObject.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/PromiseCapability.h>
#include <LibJS/Runtime/PromiseConstructor.h>
#include <LibJS/Runtime/Value.h>
namespace JS {
NonnullGCPtr<ECMAScriptFunctionObject> ECMAScriptFunctionObject::create(Realm& realm, FlyString name, DeprecatedString source_text, Statement const& ecmascript_code, Vector<FunctionParameter> parameters, i32 m_function_length, Environment* parent_environment, PrivateEnvironment* private_environment, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function, Variant<PropertyKey, PrivateName, Empty> class_field_initializer_name)
{
Object* prototype = nullptr;
switch (kind) {
case FunctionKind::Normal:
prototype = realm.intrinsics().function_prototype();
break;
case FunctionKind::Generator:
prototype = realm.intrinsics().generator_function_prototype();
break;
case FunctionKind::Async:
prototype = realm.intrinsics().async_function_prototype();
break;
case FunctionKind::AsyncGenerator:
prototype = realm.intrinsics().async_generator_function_prototype();
break;
}
return *realm.heap().allocate<ECMAScriptFunctionObject>(realm, move(name), move(source_text), ecmascript_code, move(parameters), m_function_length, parent_environment, private_environment, *prototype, kind, is_strict, might_need_arguments_object, contains_direct_call_to_eval, is_arrow_function, move(class_field_initializer_name));
}
NonnullGCPtr<ECMAScriptFunctionObject> ECMAScriptFunctionObject::create(Realm& realm, FlyString name, Object& prototype, DeprecatedString source_text, Statement const& ecmascript_code, Vector<FunctionParameter> parameters, i32 m_function_length, Environment* parent_environment, PrivateEnvironment* private_environment, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function, Variant<PropertyKey, PrivateName, Empty> class_field_initializer_name)
{
return *realm.heap().allocate<ECMAScriptFunctionObject>(realm, move(name), move(source_text), ecmascript_code, move(parameters), m_function_length, parent_environment, private_environment, prototype, kind, is_strict, might_need_arguments_object, contains_direct_call_to_eval, is_arrow_function, move(class_field_initializer_name));
}
ECMAScriptFunctionObject::ECMAScriptFunctionObject(FlyString name, DeprecatedString source_text, Statement const& ecmascript_code, Vector<FunctionParameter> formal_parameters, i32 function_length, Environment* parent_environment, PrivateEnvironment* private_environment, Object& prototype, FunctionKind kind, bool strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function, Variant<PropertyKey, PrivateName, Empty> class_field_initializer_name)
: FunctionObject(prototype)
, m_name(move(name))
, m_function_length(function_length)
, m_environment(parent_environment)
, m_private_environment(private_environment)
, m_formal_parameters(move(formal_parameters))
, m_ecmascript_code(ecmascript_code)
, m_realm(&prototype.shape().realm())
, m_source_text(move(source_text))
, m_class_field_initializer_name(move(class_field_initializer_name))
, m_strict(strict)
, m_might_need_arguments_object(might_need_arguments_object)
, m_contains_direct_call_to_eval(contains_direct_call_to_eval)
, m_is_arrow_function(is_arrow_function)
, m_kind(kind)
{
// NOTE: This logic is from OrdinaryFunctionCreate, https://tc39.es/ecma262/#sec-ordinaryfunctioncreate
// 9. If thisMode is lexical-this, set F.[[ThisMode]] to lexical.
if (m_is_arrow_function)
m_this_mode = ThisMode::Lexical;
// 10. Else if Strict is true, set F.[[ThisMode]] to strict.
else if (m_strict)
m_this_mode = ThisMode::Strict;
else
// 11. Else, set F.[[ThisMode]] to global.
m_this_mode = ThisMode::Global;
// 15. Set F.[[ScriptOrModule]] to GetActiveScriptOrModule().
m_script_or_module = vm().get_active_script_or_module();
// 15.1.3 Static Semantics: IsSimpleParameterList, https://tc39.es/ecma262/#sec-static-semantics-issimpleparameterlist
m_has_simple_parameter_list = all_of(m_formal_parameters, [&](auto& parameter) {
if (parameter.is_rest)
return false;
if (parameter.default_value)
return false;
if (!parameter.binding.template has<FlyString>())
return false;
return true;
});
}
void ECMAScriptFunctionObject::initialize(Realm& realm)
{
auto& vm = this->vm();
Base::initialize(realm);
// Note: The ordering of these properties must be: length, name, prototype which is the order
// they are defined in the spec: https://tc39.es/ecma262/#sec-function-instances .
// This is observable through something like: https://tc39.es/ecma262/#sec-ordinaryownpropertykeys
// which must give the properties in chronological order which in this case is the order they
// are defined in the spec.
MUST(define_property_or_throw(vm.names.length, { .value = Value(m_function_length), .writable = false, .enumerable = false, .configurable = true }));
MUST(define_property_or_throw(vm.names.name, { .value = PrimitiveString::create(vm, m_name.is_null() ? "" : m_name), .writable = false, .enumerable = false, .configurable = true }));
if (!m_is_arrow_function) {
Object* prototype = nullptr;
switch (m_kind) {
case FunctionKind::Normal:
prototype = vm.heap().allocate<Object>(realm, *realm.intrinsics().new_ordinary_function_prototype_object_shape());
MUST(prototype->define_property_or_throw(vm.names.constructor, { .value = this, .writable = true, .enumerable = false, .configurable = true }));
break;
case FunctionKind::Generator:
// prototype is "g1.prototype" in figure-2 (https://tc39.es/ecma262/img/figure-2.png)
prototype = Object::create(realm, realm.intrinsics().generator_function_prototype_prototype());
break;
case FunctionKind::Async:
break;
case FunctionKind::AsyncGenerator:
prototype = Object::create(realm, realm.intrinsics().async_generator_function_prototype_prototype());
break;
}
// 27.7.4 AsyncFunction Instances, https://tc39.es/ecma262/#sec-async-function-instances
// AsyncFunction instances do not have a prototype property as they are not constructible.
if (m_kind != FunctionKind::Async)
define_direct_property(vm.names.prototype, prototype, Attribute::Writable);
}
}
// 10.2.1 [[Call]] ( thisArgument, argumentsList ), https://tc39.es/ecma262/#sec-ecmascript-function-objects-call-thisargument-argumentslist
ThrowCompletionOr<Value> ECMAScriptFunctionObject::internal_call(Value this_argument, MarkedVector<Value> arguments_list)
{
auto& vm = this->vm();
// 1. Let callerContext be the running execution context.
// NOTE: No-op, kept by the VM in its execution context stack.
ExecutionContext callee_context(heap());
// Non-standard
callee_context.arguments.extend(move(arguments_list));
if (auto* interpreter = vm.interpreter_if_exists())
callee_context.current_node = interpreter->current_node();
// 2. Let calleeContext be PrepareForOrdinaryCall(F, undefined).
// NOTE: We throw if the end of the native stack is reached, so unlike in the spec this _does_ need an exception check.
TRY(prepare_for_ordinary_call(callee_context, nullptr));
// 3. Assert: calleeContext is now the running execution context.
VERIFY(&vm.running_execution_context() == &callee_context);
// 4. If F.[[IsClassConstructor]] is true, then
if (m_is_class_constructor) {
// a. Let error be a newly created TypeError object.
// b. NOTE: error is created in calleeContext with F's associated Realm Record.
auto throw_completion = vm.throw_completion<TypeError>(ErrorType::ClassConstructorWithoutNew, m_name);
// c. Remove calleeContext from the execution context stack and restore callerContext as the running execution context.
vm.pop_execution_context();
// d. Return ThrowCompletion(error).
return throw_completion;
}
// 5. Perform OrdinaryCallBindThis(F, calleeContext, thisArgument).
ordinary_call_bind_this(callee_context, this_argument);
// 6. Let result be Completion(OrdinaryCallEvaluateBody(F, argumentsList)).
auto result = ordinary_call_evaluate_body();
// 7. Remove calleeContext from the execution context stack and restore callerContext as the running execution context.
vm.pop_execution_context();
// 8. If result.[[Type]] is return, return result.[[Value]].
if (result.type() == Completion::Type::Return)
return result.value();
// 9. ReturnIfAbrupt(result).
if (result.is_abrupt()) {
VERIFY(result.is_error());
return result;
}
// 10. Return undefined.
return js_undefined();
}
// 10.2.2 [[Construct]] ( argumentsList, newTarget ), https://tc39.es/ecma262/#sec-ecmascript-function-objects-construct-argumentslist-newtarget
ThrowCompletionOr<Object*> ECMAScriptFunctionObject::internal_construct(MarkedVector<Value> arguments_list, FunctionObject& new_target)
{
auto& vm = this->vm();
// 1. Let callerContext be the running execution context.
// NOTE: No-op, kept by the VM in its execution context stack.
// 2. Let kind be F.[[ConstructorKind]].
auto kind = m_constructor_kind;
Object* this_argument = nullptr;
// 3. If kind is base, then
if (kind == ConstructorKind::Base) {
// a. Let thisArgument be ? OrdinaryCreateFromConstructor(newTarget, "%Object.prototype%").
this_argument = TRY(ordinary_create_from_constructor<Object>(vm, new_target, &Intrinsics::object_prototype));
}
ExecutionContext callee_context(heap());
// Non-standard
callee_context.arguments.extend(move(arguments_list));
if (auto* interpreter = vm.interpreter_if_exists())
callee_context.current_node = interpreter->current_node();
// 4. Let calleeContext be PrepareForOrdinaryCall(F, newTarget).
// NOTE: We throw if the end of the native stack is reached, so unlike in the spec this _does_ need an exception check.
TRY(prepare_for_ordinary_call(callee_context, &new_target));
// 5. Assert: calleeContext is now the running execution context.
VERIFY(&vm.running_execution_context() == &callee_context);
// 6. If kind is base, then
if (kind == ConstructorKind::Base) {
// a. Perform OrdinaryCallBindThis(F, calleeContext, thisArgument).
ordinary_call_bind_this(callee_context, this_argument);
// b. Let initializeResult be Completion(InitializeInstanceElements(thisArgument, F)).
auto initialize_result = this_argument->initialize_instance_elements(*this);
// c. If initializeResult is an abrupt completion, then
if (initialize_result.is_throw_completion()) {
// i. Remove calleeContext from the execution context stack and restore callerContext as the running execution context.
vm.pop_execution_context();
// ii. Return ? initializeResult.
return initialize_result.throw_completion();
}
}
// 7. Let constructorEnv be the LexicalEnvironment of calleeContext.
auto* constructor_env = callee_context.lexical_environment;
// 8. Let result be Completion(OrdinaryCallEvaluateBody(F, argumentsList)).
auto result = ordinary_call_evaluate_body();
// 9. Remove calleeContext from the execution context stack and restore callerContext as the running execution context.
vm.pop_execution_context();
// 10. If result.[[Type]] is return, then
if (result.type() == Completion::Type::Return) {
// FIXME: This is leftover from untangling the call/construct mess - doesn't belong here in any way, but removing it breaks derived classes.
// Likely fixed by making ClassDefinitionEvaluation fully spec compliant.
if (kind == ConstructorKind::Derived && result.value()->is_object()) {
auto prototype = TRY(new_target.get(vm.names.prototype));
if (prototype.is_object())
TRY(result.value()->as_object().internal_set_prototype_of(&prototype.as_object()));
}
// EOF (End of FIXME)
// a. If Type(result.[[Value]]) is Object, return result.[[Value]].
if (result.value()->is_object())
return &result.value()->as_object();
// b. If kind is base, return thisArgument.
if (kind == ConstructorKind::Base)
return this_argument;
// c. If result.[[Value]] is not undefined, throw a TypeError exception.
if (!result.value()->is_undefined())
return vm.throw_completion<TypeError>(ErrorType::DerivedConstructorReturningInvalidValue);
}
// 11. Else, ReturnIfAbrupt(result).
else if (result.is_abrupt()) {
VERIFY(result.is_error());
return result;
}
// 12. Let thisBinding be ? constructorEnv.GetThisBinding().
auto this_binding = TRY(constructor_env->get_this_binding(vm));
// 13. Assert: Type(thisBinding) is Object.
VERIFY(this_binding.is_object());
// 14. Return thisBinding.
return &this_binding.as_object();
}
void ECMAScriptFunctionObject::visit_edges(Visitor& visitor)
{
Base::visit_edges(visitor);
visitor.visit(m_environment);
visitor.visit(m_private_environment);
visitor.visit(m_realm);
visitor.visit(m_home_object);
for (auto& field : m_fields) {
if (auto* property_key_ptr = field.name.get_pointer<PropertyKey>(); property_key_ptr && property_key_ptr->is_symbol())
visitor.visit(property_key_ptr->as_symbol());
}
m_script_or_module.visit(
[](Empty) {},
[&](auto& script_or_module) {
visitor.visit(script_or_module.ptr());
});
}
// 10.2.7 MakeMethod ( F, homeObject ), https://tc39.es/ecma262/#sec-makemethod
void ECMAScriptFunctionObject::make_method(Object& home_object)
{
// 1. Set F.[[HomeObject]] to homeObject.
m_home_object = &home_object;
// 2. Return unused.
}
// 10.2.11 FunctionDeclarationInstantiation ( func, argumentsList ), https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantiation(Interpreter* interpreter)
{
auto& vm = this->vm();
auto& realm = *vm.current_realm();
auto& callee_context = vm.running_execution_context();
// Needed to extract declarations and functions
ScopeNode const* scope_body = nullptr;
if (is<ScopeNode>(*m_ecmascript_code))
scope_body = static_cast<ScopeNode const*>(m_ecmascript_code.ptr());
bool has_parameter_expressions = false;
// FIXME: Maybe compute has duplicates at parse time? (We need to anyway since it's an error in some cases)
bool has_duplicates = false;
HashTable<FlyString> parameter_names;
for (auto& parameter : m_formal_parameters) {
if (parameter.default_value)
has_parameter_expressions = true;
parameter.binding.visit(
[&](FlyString const& name) {
if (parameter_names.set(name) != AK::HashSetResult::InsertedNewEntry)
has_duplicates = true;
},
[&](NonnullRefPtr<BindingPattern> const& pattern) {
if (pattern->contains_expression())
has_parameter_expressions = true;
pattern->for_each_bound_name([&](auto& name) {
if (parameter_names.set(name) != AK::HashSetResult::InsertedNewEntry)
has_duplicates = true;
});
});
}
auto arguments_object_needed = m_might_need_arguments_object;
if (this_mode() == ThisMode::Lexical)
arguments_object_needed = false;
if (parameter_names.contains(vm.names.arguments.as_string()))
arguments_object_needed = false;
HashTable<FlyString> function_names;
Vector<FunctionDeclaration const&> functions_to_initialize;
if (scope_body) {
scope_body->for_each_var_function_declaration_in_reverse_order([&](FunctionDeclaration const& function) {
if (function_names.set(function.name()) == AK::HashSetResult::InsertedNewEntry)
functions_to_initialize.append(function);
});
auto const& arguments_name = vm.names.arguments.as_string();
if (!has_parameter_expressions && function_names.contains(arguments_name))
arguments_object_needed = false;
if (!has_parameter_expressions && arguments_object_needed) {
scope_body->for_each_lexically_declared_name([&](auto const& name) {
if (name == arguments_name)
arguments_object_needed = false;
});
}
} else {
arguments_object_needed = false;
}
Environment* environment;
if (is_strict_mode() || !has_parameter_expressions) {
environment = callee_context.lexical_environment;
} else {
environment = new_declarative_environment(*callee_context.lexical_environment);
VERIFY(callee_context.variable_environment == callee_context.lexical_environment);
callee_context.lexical_environment = environment;
}
for (auto const& parameter_name : parameter_names) {
if (MUST(environment->has_binding(parameter_name)))
continue;
MUST(environment->create_mutable_binding(vm, parameter_name, false));
if (has_duplicates)
MUST(environment->initialize_binding(vm, parameter_name, js_undefined()));
}
if (arguments_object_needed) {
Object* arguments_object;
if (is_strict_mode() || !has_simple_parameter_list())
arguments_object = create_unmapped_arguments_object(vm, vm.running_execution_context().arguments);
else
arguments_object = create_mapped_arguments_object(vm, *this, formal_parameters(), vm.running_execution_context().arguments, *environment);
if (is_strict_mode())
MUST(environment->create_immutable_binding(vm, vm.names.arguments.as_string(), false));
else
MUST(environment->create_mutable_binding(vm, vm.names.arguments.as_string(), false));
MUST(environment->initialize_binding(vm, vm.names.arguments.as_string(), arguments_object));
parameter_names.set(vm.names.arguments.as_string());
}
// We now treat parameterBindings as parameterNames.
// The spec makes an iterator here to do IteratorBindingInitialization but we just do it manually
auto& execution_context_arguments = vm.running_execution_context().arguments;
size_t default_parameter_index = 0;
for (size_t i = 0; i < m_formal_parameters.size(); ++i) {
auto& parameter = m_formal_parameters[i];
if (parameter.default_value)
++default_parameter_index;
TRY(parameter.binding.visit(
[&](auto const& param) -> ThrowCompletionOr<void> {
Value argument_value;
if (parameter.is_rest) {
auto array = MUST(Array::create(realm, 0));
for (size_t rest_index = i; rest_index < execution_context_arguments.size(); ++rest_index)
array->indexed_properties().append(execution_context_arguments[rest_index]);
argument_value = array;
} else if (i < execution_context_arguments.size() && !execution_context_arguments[i].is_undefined()) {
argument_value = execution_context_arguments[i];
} else if (parameter.default_value) {
if (auto* bytecode_interpreter = Bytecode::Interpreter::current()) {
auto value_and_frame = bytecode_interpreter->run_and_return_frame(*m_default_parameter_bytecode_executables[default_parameter_index - 1], nullptr);
if (value_and_frame.value.is_error())
return value_and_frame.value.release_error();
// Resulting value is in the accumulator.
argument_value = value_and_frame.frame->registers.at(0);
} else if (interpreter) {
argument_value = TRY(parameter.default_value->execute(*interpreter)).release_value();
}
} else {
argument_value = js_undefined();
}
Environment* used_environment = has_duplicates ? nullptr : environment;
if constexpr (IsSame<FlyString const&, decltype(param)>) {
Reference reference = TRY(vm.resolve_binding(param, used_environment));
// Here the difference from hasDuplicates is important
if (has_duplicates)
return reference.put_value(vm, argument_value);
else
return reference.initialize_referenced_binding(vm, argument_value);
} else if (IsSame<NonnullRefPtr<BindingPattern> const&, decltype(param)>) {
// Here the difference from hasDuplicates is important
return vm.binding_initialization(param, argument_value, used_environment);
}
}));
}
Environment* var_environment;
HashTable<FlyString> instantiated_var_names;
if (scope_body)
instantiated_var_names.ensure_capacity(scope_body->var_declaration_count());
if (!has_parameter_expressions) {
if (scope_body) {
scope_body->for_each_var_declared_name([&](auto const& name) {
if (!parameter_names.contains(name) && instantiated_var_names.set(name) == AK::HashSetResult::InsertedNewEntry) {
MUST(environment->create_mutable_binding(vm, name, false));
MUST(environment->initialize_binding(vm, name, js_undefined()));
}
});
}
var_environment = environment;
} else {
var_environment = new_declarative_environment(*environment);
callee_context.variable_environment = var_environment;
if (scope_body) {
scope_body->for_each_var_declared_name([&](auto const& name) {
if (instantiated_var_names.set(name) != AK::HashSetResult::InsertedNewEntry)
return;
MUST(var_environment->create_mutable_binding(vm, name, false));
Value initial_value;
if (!parameter_names.contains(name) || function_names.contains(name))
initial_value = js_undefined();
else
initial_value = MUST(environment->get_binding_value(vm, name, false));
MUST(var_environment->initialize_binding(vm, name, initial_value));
});
}
}
// B.3.2.1 Changes to FunctionDeclarationInstantiation, https://tc39.es/ecma262/#sec-web-compat-functiondeclarationinstantiation
if (!m_strict && scope_body) {
scope_body->for_each_function_hoistable_with_annexB_extension([&](FunctionDeclaration& function_declaration) {
auto& function_name = function_declaration.name();
if (parameter_names.contains(function_name))
return;
// The spec says 'initializedBindings' here but that does not exist and it then adds it to 'instantiatedVarNames' so it probably means 'instantiatedVarNames'.
if (!instantiated_var_names.contains(function_name) && function_name != vm.names.arguments.as_string()) {
MUST(var_environment->create_mutable_binding(vm, function_name, false));
MUST(var_environment->initialize_binding(vm, function_name, js_undefined()));
instantiated_var_names.set(function_name);
}
function_declaration.set_should_do_additional_annexB_steps();
});
}
Environment* lex_environment;
// 30. If strict is false, then
if (!is_strict_mode()) {
// Optimization: We avoid creating empty top-level declarative environments in non-strict mode, if both of these conditions are true:
// 1. there is no direct call to eval() within this function
// 2. there are no lexical declarations that would go into the environment
bool can_elide_declarative_environment = !m_contains_direct_call_to_eval && (!scope_body || !scope_body->has_lexical_declarations());
if (can_elide_declarative_environment) {
lex_environment = var_environment;
} else {
// a. Let lexEnv be NewDeclarativeEnvironment(varEnv).
// b. NOTE: Non-strict functions use a separate Environment Record for top-level lexical declarations so that a direct eval
// can determine whether any var scoped declarations introduced by the eval code conflict with pre-existing top-level
// lexically scoped declarations. This is not needed for strict functions because a strict direct eval always places
// all declarations into a new Environment Record.
lex_environment = new_declarative_environment(*var_environment);
}
} else {
// 31. Else, let lexEnv be varEnv.
lex_environment = var_environment;
}
// 32. Set the LexicalEnvironment of calleeContext to lexEnv.
callee_context.lexical_environment = lex_environment;
if (!scope_body)
return {};
if (!Bytecode::Interpreter::current()) {
scope_body->for_each_lexically_scoped_declaration([&](Declaration const& declaration) {
declaration.for_each_bound_name([&](auto const& name) {
if (declaration.is_constant_declaration())
MUST(lex_environment->create_immutable_binding(vm, name, true));
else
MUST(lex_environment->create_mutable_binding(vm, name, false));
});
});
}
auto* private_environment = callee_context.private_environment;
for (auto& declaration : functions_to_initialize) {
auto function = ECMAScriptFunctionObject::create(realm, declaration.name(), declaration.source_text(), declaration.body(), declaration.parameters(), declaration.function_length(), lex_environment, private_environment, declaration.kind(), declaration.is_strict_mode(), declaration.might_need_arguments_object(), declaration.contains_direct_call_to_eval());
MUST(var_environment->set_mutable_binding(vm, declaration.name(), function, false));
}
if (is<DeclarativeEnvironment>(*lex_environment))
static_cast<DeclarativeEnvironment*>(lex_environment)->shrink_to_fit();
if (is<DeclarativeEnvironment>(*var_environment))
static_cast<DeclarativeEnvironment*>(var_environment)->shrink_to_fit();
return {};
}
// 10.2.1.1 PrepareForOrdinaryCall ( F, newTarget ), https://tc39.es/ecma262/#sec-prepareforordinarycall
ThrowCompletionOr<void> ECMAScriptFunctionObject::prepare_for_ordinary_call(ExecutionContext& callee_context, Object* new_target)
{
auto& vm = this->vm();
// Non-standard
callee_context.is_strict_mode = m_strict;
// 1. Let callerContext be the running execution context.
// 2. Let calleeContext be a new ECMAScript code execution context.
// NOTE: In the specification, PrepareForOrdinaryCall "returns" a new callee execution context.
// To avoid heap allocations, we put our ExecutionContext objects on the C++ stack instead.
// Whoever calls us should put an ExecutionContext on their stack and pass that as the `callee_context`.
// 3. Set the Function of calleeContext to F.
callee_context.function = this;
callee_context.function_name = m_name;
// 4. Let calleeRealm be F.[[Realm]].
auto* callee_realm = m_realm;
// NOTE: This non-standard fallback is needed until we can guarantee that literally
// every function has a realm - especially in LibWeb that's sometimes not the case
// when a function is created while no JS is running, as we currently need to rely on
// that (:acid2:, I know - see set_event_handler_attribute() for an example).
// If there's no 'current realm' either, we can't continue and crash.
if (!callee_realm)
callee_realm = vm.current_realm();
VERIFY(callee_realm);
// 5. Set the Realm of calleeContext to calleeRealm.
callee_context.realm = callee_realm;
// 6. Set the ScriptOrModule of calleeContext to F.[[ScriptOrModule]].
callee_context.script_or_module = m_script_or_module;
// 7. Let localEnv be NewFunctionEnvironment(F, newTarget).
auto* local_environment = new_function_environment(*this, new_target);
// 8. Set the LexicalEnvironment of calleeContext to localEnv.
callee_context.lexical_environment = local_environment;
// 9. Set the VariableEnvironment of calleeContext to localEnv.
callee_context.variable_environment = local_environment;
// 10. Set the PrivateEnvironment of calleeContext to F.[[PrivateEnvironment]].
callee_context.private_environment = m_private_environment;
// 11. If callerContext is not already suspended, suspend callerContext.
// FIXME: We don't have this concept yet.
// 12. Push calleeContext onto the execution context stack; calleeContext is now the running execution context.
TRY(vm.push_execution_context(callee_context, {}));
// 13. NOTE: Any exception objects produced after this point are associated with calleeRealm.
// 14. Return calleeContext.
// NOTE: See the comment after step 2 above about how contexts are allocated on the C++ stack.
return {};
}
// 10.2.1.2 OrdinaryCallBindThis ( F, calleeContext, thisArgument ), https://tc39.es/ecma262/#sec-ordinarycallbindthis
void ECMAScriptFunctionObject::ordinary_call_bind_this(ExecutionContext& callee_context, Value this_argument)
{
auto& vm = this->vm();
// 1. Let thisMode be F.[[ThisMode]].
auto this_mode = m_this_mode;
// If thisMode is lexical, return unused.
if (this_mode == ThisMode::Lexical)
return;
// 3. Let calleeRealm be F.[[Realm]].
auto* callee_realm = m_realm;
// NOTE: This non-standard fallback is needed until we can guarantee that literally
// every function has a realm - especially in LibWeb that's sometimes not the case
// when a function is created while no JS is running, as we currently need to rely on
// that (:acid2:, I know - see set_event_handler_attribute() for an example).
// If there's no 'current realm' either, we can't continue and crash.
if (!callee_realm)
callee_realm = vm.current_realm();
VERIFY(callee_realm);
// 4. Let localEnv be the LexicalEnvironment of calleeContext.
auto* local_env = callee_context.lexical_environment;
Value this_value;
// 5. If thisMode is strict, let thisValue be thisArgument.
if (this_mode == ThisMode::Strict) {
this_value = this_argument;
}
// 6. Else,
else {
// a. If thisArgument is undefined or null, then
if (this_argument.is_nullish()) {
// i. Let globalEnv be calleeRealm.[[GlobalEnv]].
// ii. Assert: globalEnv is a global Environment Record.
auto& global_env = callee_realm->global_environment();
// iii. Let thisValue be globalEnv.[[GlobalThisValue]].
this_value = &global_env.global_this_value();
}
// b. Else,
else {
// i. Let thisValue be ! ToObject(thisArgument).
this_value = MUST(this_argument.to_object(vm));
// ii. NOTE: ToObject produces wrapper objects using calleeRealm.
VERIFY(vm.current_realm() == callee_realm);
}
}
// 7. Assert: localEnv is a function Environment Record.
// 8. Assert: The next step never returns an abrupt completion because localEnv.[[ThisBindingStatus]] is not initialized.
// 9. Perform ! localEnv.BindThisValue(thisValue).
MUST(verify_cast<FunctionEnvironment>(local_env)->bind_this_value(vm, this_value));
// 10. Return unused.
}
// 27.7.5.1 AsyncFunctionStart ( promiseCapability, asyncFunctionBody ), https://tc39.es/ecma262/#sec-async-functions-abstract-operations-async-function-start
void ECMAScriptFunctionObject::async_function_start(PromiseCapability const& promise_capability)
{
auto& vm = this->vm();
// 1. Let runningContext be the running execution context.
auto& running_context = vm.running_execution_context();
// 2. Let asyncContext be a copy of runningContext.
auto async_context = running_context.copy();
// 3. NOTE: Copying the execution state is required for AsyncBlockStart to resume its execution. It is ill-defined to resume a currently executing context.
// 4. Perform AsyncBlockStart(promiseCapability, asyncFunctionBody, asyncContext).
async_block_start(vm, m_ecmascript_code, promise_capability, async_context);
// 5. Return unused.
}
// 27.7.5.2 AsyncBlockStart ( promiseCapability, asyncBody, asyncContext ), https://tc39.es/ecma262/#sec-asyncblockstart
void async_block_start(VM& vm, NonnullRefPtr<Statement> const& async_body, PromiseCapability const& promise_capability, ExecutionContext& async_context)
{
auto& realm = *vm.current_realm();
// 1. Assert: promiseCapability is a PromiseCapability Record.
// 2. Let runningContext be the running execution context.
auto& running_context = vm.running_execution_context();
// 3. Set the code evaluation state of asyncContext such that when evaluation is resumed for that execution context the following steps will be performed:
auto* execution_steps = NativeFunction::create(realm, "", [&async_body, &promise_capability](auto& vm) -> ThrowCompletionOr<Value> {
// a. Let result be the result of evaluating asyncBody.
auto result = async_body->execute(vm.interpreter());
// b. Assert: If we return here, the async function either threw an exception or performed an implicit or explicit return; all awaiting is done.
// c. Remove asyncContext from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
vm.pop_execution_context();
// d. If result.[[Type]] is normal, then
if (result.type() == Completion::Type::Normal) {
// i. Perform ! Call(promiseCapability.[[Resolve]], undefined, « undefined »).
MUST(call(vm, *promise_capability.resolve(), js_undefined(), js_undefined()));
}
// e. Else if result.[[Type]] is return, then
else if (result.type() == Completion::Type::Return) {
// i. Perform ! Call(promiseCapability.[[Resolve]], undefined, « result.[[Value]] »).
MUST(call(vm, *promise_capability.resolve(), js_undefined(), *result.value()));
}
// f. Else,
else {
// i. Assert: result.[[Type]] is throw.
VERIFY(result.type() == Completion::Type::Throw);
// ii. Perform ! Call(promiseCapability.[[Reject]], undefined, « result.[[Value]] »).
MUST(call(vm, *promise_capability.reject(), js_undefined(), *result.value()));
}
// g. Return unused.
// NOTE: We don't support returning an empty/optional/unused value here.
return js_undefined();
});
// 4. Push asyncContext onto the execution context stack; asyncContext is now the running execution context.
auto push_result = vm.push_execution_context(async_context, {});
if (push_result.is_error())
return;
// 5. Resume the suspended evaluation of asyncContext. Let result be the value returned by the resumed computation.
auto result = call(vm, *execution_steps, async_context.this_value.is_empty() ? js_undefined() : async_context.this_value);
// 6. Assert: When we return here, asyncContext has already been removed from the execution context stack and runningContext is the currently running execution context.
VERIFY(&vm.running_execution_context() == &running_context);
// 7. Assert: result is a normal completion with a value of unused. The possible sources of this value are Await or, if the async function doesn't await anything, step 3.g above.
VERIFY(result.has_value() && result.value().is_undefined());
// 8. Return unused.
}
// 10.2.1.4 OrdinaryCallEvaluateBody ( F, argumentsList ), https://tc39.es/ecma262/#sec-ordinarycallevaluatebody
// 15.8.4 Runtime Semantics: EvaluateAsyncFunctionBody, https://tc39.es/ecma262/#sec-runtime-semantics-evaluatefunctionbody
Completion ECMAScriptFunctionObject::ordinary_call_evaluate_body()
{
auto& vm = this->vm();
auto& realm = *vm.current_realm();
if (m_kind == FunctionKind::AsyncGenerator)
return vm.throw_completion<InternalError>(ErrorType::NotImplemented, "Async Generator function execution");
auto* bytecode_interpreter = Bytecode::Interpreter::current();
// The bytecode interpreter can execute generator functions while the AST interpreter cannot.
// This simply makes it create a new bytecode interpreter when one doesn't exist when executing a generator function.
// Doing so makes it automatically switch to the bytecode interpreter to execute any future code until it exits the generator. See below.
// This allows us to keep all of the existing functionality that works in AST while adding generator support on top of it.
// However, this does cause an awkward situation with features not supported in bytecode, where features that work outside of generators with AST
// suddenly stop working inside of generators.
// This is a stop gap until bytecode mode becomes the default.
OwnPtr<Bytecode::Interpreter> temp_bc_interpreter;
if (m_kind == FunctionKind::Generator && !bytecode_interpreter) {
temp_bc_interpreter = make<Bytecode::Interpreter>(realm);
bytecode_interpreter = temp_bc_interpreter.ptr();
}
if (bytecode_interpreter) {
if (!m_bytecode_executable) {
auto compile = [&](auto& node, auto kind, auto name) -> ThrowCompletionOr<NonnullOwnPtr<Bytecode::Executable>> {
auto executable_result = Bytecode::Generator::generate(node, kind);
if (executable_result.is_error())
return vm.throw_completion<InternalError>(ErrorType::NotImplemented, executable_result.error().to_deprecated_string());
auto bytecode_executable = executable_result.release_value();
bytecode_executable->name = name;
auto& passes = Bytecode::Interpreter::optimization_pipeline();
passes.perform(*bytecode_executable);
if constexpr (JS_BYTECODE_DEBUG) {
dbgln("Optimisation passes took {}us", passes.elapsed());
dbgln("Compiled Bytecode::Block for function '{}':", m_name);
}
if (Bytecode::g_dump_bytecode)
bytecode_executable->dump();
return bytecode_executable;
};
m_bytecode_executable = TRY(compile(*m_ecmascript_code, m_kind, m_name));
size_t default_parameter_index = 0;
for (auto& parameter : m_formal_parameters) {
if (!parameter.default_value)
continue;
auto executable = TRY(compile(*parameter.default_value, FunctionKind::Normal, DeprecatedString::formatted("default parameter #{} for {}", default_parameter_index, m_name)));
m_default_parameter_bytecode_executables.append(move(executable));
}
}
TRY(function_declaration_instantiation(nullptr));
auto result_and_frame = bytecode_interpreter->run_and_return_frame(*m_bytecode_executable, nullptr);
VERIFY(result_and_frame.frame != nullptr);
if (result_and_frame.value.is_error())
return result_and_frame.value.release_error();
auto result = result_and_frame.value.release_value();
// NOTE: Running the bytecode should eventually return a completion.
// Until it does, we assume "return" and include the undefined fallback from the call site.
if (m_kind == FunctionKind::Normal)
return { Completion::Type::Return, result.value_or(js_undefined()), {} };
auto generator_object = TRY(GeneratorObject::create(realm, result, this, vm.running_execution_context().copy(), move(*result_and_frame.frame)));
// NOTE: Async functions are entirely transformed to generator functions, and wrapped in a custom driver that returns a promise
// See AwaitExpression::generate_bytecode() for the transformation.
if (m_kind == FunctionKind::Async)
return { Completion::Type::Return, TRY(AsyncFunctionDriverWrapper::create(realm, generator_object)), {} };
VERIFY(m_kind == FunctionKind::Generator);
return { Completion::Type::Return, generator_object, {} };
} else {
if (m_kind == FunctionKind::Generator)
return vm.throw_completion<InternalError>(ErrorType::NotImplemented, "Generator function execution in AST interpreter");
OwnPtr<Interpreter> local_interpreter;
Interpreter* ast_interpreter = vm.interpreter_if_exists();
if (!ast_interpreter) {
local_interpreter = Interpreter::create_with_existing_realm(realm);
ast_interpreter = local_interpreter.ptr();
}
VM::InterpreterExecutionScope scope(*ast_interpreter);
// FunctionBody : FunctionStatementList
if (m_kind == FunctionKind::Normal) {
// 1. Perform ? FunctionDeclarationInstantiation(functionObject, argumentsList).
TRY(function_declaration_instantiation(ast_interpreter));
// 2. Return the result of evaluating FunctionStatementList.
return m_ecmascript_code->execute(*ast_interpreter);
}
// AsyncFunctionBody : FunctionBody
else if (m_kind == FunctionKind::Async) {
// 1. Let promiseCapability be ! NewPromiseCapability(%Promise%).
auto promise_capability = MUST(new_promise_capability(vm, realm.intrinsics().promise_constructor()));
// 2. Let declResult be Completion(FunctionDeclarationInstantiation(functionObject, argumentsList)).
auto declaration_result = function_declaration_instantiation(ast_interpreter);
// 3. If declResult is an abrupt completion, then
if (declaration_result.is_throw_completion()) {
// a. Perform ! Call(promiseCapability.[[Reject]], undefined, « declResult.[[Value]] »).
MUST(call(vm, *promise_capability->reject(), js_undefined(), *declaration_result.throw_completion().value()));
}
// 4. Else,
else {
// a. Perform AsyncFunctionStart(promiseCapability, FunctionBody).
async_function_start(promise_capability);
}
// 5. Return Completion Record { [[Type]]: return, [[Value]]: promiseCapability.[[Promise]], [[Target]]: empty }.
return Completion { Completion::Type::Return, promise_capability->promise(), {} };
}
}
VERIFY_NOT_REACHED();
}
void ECMAScriptFunctionObject::set_name(FlyString const& name)
{
VERIFY(!name.is_null());
auto& vm = this->vm();
m_name = name;
MUST(define_property_or_throw(vm.names.name, { .value = PrimitiveString::create(vm, m_name), .writable = false, .enumerable = false, .configurable = true }));
}
}
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