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ladybird/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
davidot 9264f9d24e LibJS+Everywhere: Remove VM::exception() and most related functions 
This commit removes all exception related code:
Remove VM::exception(), VM::throw_exception() etc. Any leftover
throw_exception calls are moved to throw_completion.
The one method left is clear_exception() which is now a no-op. Most of
these calls are just to clear whatever exception might have been thrown
when handling a Completion. So to have a cleaner commit this will be
removed in a next commit.

It also removes the actual Exception and TemporaryClearException classes
since these are no longer used.

In any spot where the exception was actually used an attempt was made to
preserve that behavior. However since it is no longer tracked by the VM
we cannot access exceptions which were thrown in previous calls.
There are two such cases which might have different behavior:
- In Web::DOM::Document::interpreter() the on_call_stack_emptied hook
  used to print any uncaught exception but this is now no longer
  possible as the VM does not store uncaught exceptions.
- In js the code used to be interruptable by throwing an exception on
  the VM. This is no longer possible but was already somewhat fragile
  before as you could happen to throw an exception just before a VERIFY.
2022-02-08 09:12:42 +00:00

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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/GeneratorPrototype.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/PromiseConstructor.h>
#include <LibJS/Runtime/PromiseReaction.h>
#include <LibJS/Runtime/Value.h>
namespace JS {
ECMAScriptFunctionObject* ECMAScriptFunctionObject::create(GlobalObject& global_object, FlyString name, String source_text, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, PrivateEnvironment* private_scope, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function)
{
Object* prototype = nullptr;
switch (kind) {
case FunctionKind::Normal:
prototype = global_object.function_prototype();
break;
case FunctionKind::Generator:
prototype = global_object.generator_function_prototype();
break;
case FunctionKind::Async:
prototype = global_object.async_function_prototype();
break;
case FunctionKind::AsyncGenerator:
prototype = global_object.async_generator_function_prototype();
break;
}
return global_object.heap().allocate<ECMAScriptFunctionObject>(global_object, move(name), move(source_text), ecmascript_code, move(parameters), m_function_length, parent_scope, private_scope, *prototype, kind, is_strict, might_need_arguments_object, contains_direct_call_to_eval, is_arrow_function);
}
ECMAScriptFunctionObject* ECMAScriptFunctionObject::create(GlobalObject& global_object, FlyString name, Object& prototype, String source_text, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, PrivateEnvironment* private_scope, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function)
{
return global_object.heap().allocate<ECMAScriptFunctionObject>(global_object, move(name), move(source_text), ecmascript_code, move(parameters), m_function_length, parent_scope, private_scope, prototype, kind, is_strict, might_need_arguments_object, contains_direct_call_to_eval, is_arrow_function);
}
ECMAScriptFunctionObject::ECMAScriptFunctionObject(FlyString name, String source_text, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> formal_parameters, i32 function_length, Environment* parent_scope, PrivateEnvironment* private_scope, Object& prototype, FunctionKind kind, bool strict, bool might_need_arguments_object, bool contains_direct_call_to_eval, bool is_arrow_function)
: FunctionObject(prototype)
, m_name(move(name))
, m_function_length(function_length)
, m_environment(parent_scope)
, m_private_environment(private_scope)
, m_formal_parameters(move(formal_parameters))
, m_ecmascript_code(ecmascript_code)
, m_realm(global_object().associated_realm())
, m_source_text(move(source_text))
, 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(GlobalObject& global_object)
{
auto& vm = this->vm();
Base::initialize(global_object);
// 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 = js_string(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>(global_object, *global_object.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 = global_object.generator_prototype();
break;
case FunctionKind::Async:
break;
case FunctionKind::AsyncGenerator:
// FIXME: Add the AsyncGeneratorObject and set it as prototype.
break;
}
define_direct_property(vm.names.prototype, prototype, Attribute::Writable);
}
}
ECMAScriptFunctionObject::~ECMAScriptFunctionObject()
{
}
// 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, MarkedValueList 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>(global_object(), 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 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 NormalCompletion(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 NormalCompletion(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(MarkedValueList arguments_list, FunctionObject& new_target)
{
auto& vm = this->vm();
auto& global_object = this->global_object();
// 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>(global_object, new_target, &GlobalObject::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 InitializeInstanceElements(thisArgument, F).
auto initialize_result = vm.initialize_instance_elements(*this_argument, *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 Completion(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 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 NormalCompletion(result.[[Value]]).
if (result.value()->is_object())
return &result.value()->as_object();
// b. If kind is base, return NormalCompletion(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>(global_object, ErrorType::DerivedConstructorReturningInvalidValue);
}
// 11. Else, ReturnIfAbrupt(result).
else if (result.is_abrupt()) {
VERIFY(result.is_error());
return result;
}
// 12. Return ? constructorEnv.GetThisBinding().
auto this_binding = TRY(constructor_env->get_this_binding(global_object));
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());
visitor.visit(field.initializer);
}
}
// 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 NormalCompletion(undefined).
}
// 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& 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(global_object(), parameter_name, false));
if (has_duplicates)
MUST(environment->initialize_binding(global_object(), 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(global_object(), vm.running_execution_context().arguments);
else
arguments_object = create_mapped_arguments_object(global_object(), *this, formal_parameters(), vm.running_execution_context().arguments, *environment);
if (is_strict_mode())
MUST(environment->create_immutable_binding(global_object(), vm.names.arguments.as_string(), false));
else
MUST(environment->create_mutable_binding(global_object(), vm.names.arguments.as_string(), false));
MUST(environment->initialize_binding(global_object(), 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;
for (size_t i = 0; i < m_formal_parameters.size(); ++i) {
auto& parameter = m_formal_parameters[i];
TRY(parameter.binding.visit(
[&](auto const& param) -> ThrowCompletionOr<void> {
Value argument_value;
if (parameter.is_rest) {
auto* array = MUST(Array::create(global_object(), 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) {
// FIXME: Support default arguments in the bytecode world!
if (interpreter)
argument_value = TRY(parameter.default_value->execute(*interpreter, global_object())).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(global_object(), argument_value);
else
return reference.initialize_referenced_binding(global_object(), 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, global_object());
}
}));
}
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(global_object(), name, false));
MUST(environment->initialize_binding(global_object(), 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(global_object(), 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(global_object(), name, false));
MUST(var_environment->initialize_binding(global_object(), 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(global_object(), function_name, false));
MUST(var_environment->initialize_binding(global_object(), 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 {};
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(global_object(), name, true));
else
MUST(lex_environment->create_mutable_binding(global_object(), name, false));
});
});
auto* private_environment = callee_context.private_environment;
for (auto& declaration : functions_to_initialize) {
auto* function = ECMAScriptFunctionObject::create(global_object(), 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(global_object(), declaration.name(), function, false));
}
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, global_object()));
// 13. NOTE: Any exception objects produced after this point are associated with calleeRealm.
// 14. Return calleeContext. (See NOTE 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 NormalCompletion(undefined).
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(global_object()));
// ii. NOTE: ToObject produces wrapper objects using calleeRealm.
// FIXME: It currently doesn't, as we pass the function's global object.
}
}
// 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. Return localEnv.BindThisValue(thisValue).
MUST(verify_cast<FunctionEnvironment>(local_env)->bind_this_value(global_object(), this_value));
}
// 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);
}
// 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& global_object = vm.current_realm()->global_object();
// 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(global_object, "", [&async_body, &promise_capability](auto& vm, auto& global_object) -> ThrowCompletionOr<Value> {
// a. Let result be the result of evaluating asyncBody.
auto result = async_body->execute(vm.interpreter(), global_object);
// 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(global_object, 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(global_object, 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(global_object, promise_capability.reject, js_undefined(), *result.value()));
}
// g. Return.
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, global_object);
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(global_object, *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 undefined. The possible sources of completion values 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.
}
// 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* bytecode_interpreter = Bytecode::Interpreter::current();
if (m_kind == FunctionKind::AsyncGenerator)
return vm.throw_completion<InternalError>(global_object(), ErrorType::NotImplemented, "Async Generator function execution");
if (bytecode_interpreter) {
// FIXME: pass something to evaluate default arguments with
TRY(function_declaration_instantiation(nullptr));
if (!m_bytecode_executable) {
m_bytecode_executable = Bytecode::Generator::generate(m_ecmascript_code, m_kind);
m_bytecode_executable->name = m_name;
auto& passes = JS::Bytecode::Interpreter::optimization_pipeline();
passes.perform(*m_bytecode_executable);
if constexpr (JS_BYTECODE_DEBUG) {
dbgln("Optimisation passes took {}us", passes.elapsed());
dbgln("Compiled Bytecode::Block for function '{}':", m_name);
}
if (JS::Bytecode::g_dump_bytecode)
m_bytecode_executable->dump();
}
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(global_object(), 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(global_object(), generator_object)), {} };
VERIFY(m_kind == FunctionKind::Generator);
return { Completion::Type::Return, generator_object, {} };
} else {
if (m_kind == FunctionKind::Generator)
return vm.throw_completion<InternalError>(global_object(), 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, global_object());
}
// AsyncFunctionBody : FunctionBody
else if (m_kind == FunctionKind::Async) {
// 1. Let promiseCapability be ! NewPromiseCapability(%Promise%).
auto promise_capability = MUST(new_promise_capability(global_object(), global_object().promise_constructor()));
// 2. Let declResult be FunctionDeclarationInstantiation(functionObject, argumentsList).
auto declaration_result = function_declaration_instantiation(ast_interpreter);
// 3. If declResult is not an abrupt completion, then
if (!declaration_result.is_throw_completion()) {
// a. Perform ! AsyncFunctionStart(promiseCapability, FunctionBody).
async_function_start(promise_capability);
}
// 4. Else,
else {
// a. Perform ! Call(promiseCapability.[[Reject]], undefined, « declResult.[[Value]] »).
MUST(call(global_object(), promise_capability.reject, js_undefined(), *declaration_result.throw_completion().value()));
}
// 5. Return Completion { [[Type]]: return, [[Value]]: promiseCapability.[[Promise]], [[Target]]: empty }.
return Completion { Completion::Type::Return, promise_capability.promise, {} };
}
}
VERIFY_NOT_REACHED();
}
void ECMAScriptFunctionObject::set_name(const FlyString& name)
{
VERIFY(!name.is_null());
auto& vm = this->vm();
m_name = name;
auto success = MUST(define_property_or_throw(vm.names.name, { .value = js_string(vm, m_name), .writable = false, .enumerable = false, .configurable = true }));
VERIFY(success);
}
void ECMAScriptFunctionObject::add_field(ClassElement::ClassElementName property_key, ECMAScriptFunctionObject* initializer)
{
m_fields.empend(property_key, initializer);
}
}
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