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LibJS: Add function default arguments

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Adds the ability for function arguments to have default values. This
works for standard functions as well as arrow functions. Default values
are not printed in a <function>.toString() call, as nodes cannot print
their source string representation.
This commit is contained in:
Matthew Olsson 2020-05-02 11:46:39 -07:00 • committed by Andreas Kling
parent 751f813f6a
commit 5e66f1900b
8 changed files with 184 additions and 35 deletions
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13
Libraries/LibJS/Runtime/FunctionPrototype.cpp
View file

@ -136,9 +136,18 @@ Value FunctionPrototype::to_string(Interpreter& interpreter)
if (this_object->is_native_function() || this_object->is_bound_function()) {
function_body = String::format(" [%s]", this_object->class_name());
} else {
auto& parameters = static_cast<ScriptFunction*>(this_object)->parameters();
StringBuilder parameters_builder;
parameters_builder.join(", ", parameters);
auto first = true;
for (auto& parameter : static_cast<ScriptFunction*>(this_object)->parameters()) {
if (!first)
parameters_builder.append(", ");
first = false;
parameters_builder.append(parameter.name);
if (parameter.default_value) {
// FIXME: See note below
parameters_builder.append(" = TODO");
}
}
function_parameters = parameters_builder.build();
// FIXME: ASTNodes should be able to dump themselves to source strings - something like this:
// auto& body = static_cast<ScriptFunction*>(this_object)->body();

17
Libraries/LibJS/Runtime/ScriptFunction.cpp
View file

@ -46,12 +46,12 @@ static ScriptFunction* script_function_from(Interpreter& interpreter)
return static_cast<ScriptFunction*>(this_object);
}
ScriptFunction* ScriptFunction::create(GlobalObject& global_object, const FlyString& name, const Statement& body, Vector<FlyString> parameters, LexicalEnvironment* parent_environment)
ScriptFunction* ScriptFunction::create(GlobalObject& global_object, const FlyString& name, const Statement& body, Vector<FunctionNode::Parameter> parameters, LexicalEnvironment* parent_environment)
{
return global_object.heap().allocate<ScriptFunction>(name, body, move(parameters), parent_environment, *global_object.function_prototype());
}
ScriptFunction::ScriptFunction(const FlyString& name, const Statement& body, Vector<FlyString> parameters, LexicalEnvironment* parent_environment, Object& prototype)
ScriptFunction::ScriptFunction(const FlyString& name, const Statement& body, Vector<FunctionNode::Parameter> parameters, LexicalEnvironment* parent_environment, Object& prototype)
: Function(prototype)
, m_name(name)
, m_body(body)
@ -77,7 +77,7 @@ LexicalEnvironment* ScriptFunction::create_environment()
{
HashMap<FlyString, Variable> variables;
for (auto& parameter : m_parameters) {
variables.set(parameter, { js_undefined(), DeclarationKind::Var });
variables.set(parameter.name, { js_undefined(), DeclarationKind::Var });
}
if (body().is_scope_node()) {
@ -97,12 +97,15 @@ Value ScriptFunction::call(Interpreter& interpreter)
auto& argument_values = interpreter.call_frame().arguments;
ArgumentVector arguments;
for (size_t i = 0; i < m_parameters.size(); ++i) {
auto name = parameters()[i];
auto parameter = parameters()[i];
auto value = js_undefined();
if (i < argument_values.size())
if (i < argument_values.size() && !argument_values[i].is_undefined()) {
value = argument_values[i];
arguments.append({ name, value });
interpreter.current_environment()->set(name, { value, DeclarationKind::Var });
} else if (parameter.default_value) {
value = parameter.default_value->execute(interpreter);
}
arguments.append({ parameter.name, value });
interpreter.current_environment()->set(parameter.name, { value, DeclarationKind::Var });
}
return interpreter.run(m_body, arguments, ScopeType::Function);
}

9
Libraries/LibJS/Runtime/ScriptFunction.h
View file

@ -26,19 +26,20 @@
#pragma once
#include <LibJS/AST.h>
#include <LibJS/Runtime/Function.h>
namespace JS {
class ScriptFunction final : public Function {
public:
static ScriptFunction* create(GlobalObject&, const FlyString& name, const Statement& body, Vector<FlyString> parameters, LexicalEnvironment* parent_environment);
static ScriptFunction* create(GlobalObject&, const FlyString& name, const Statement& body, Vector<FunctionNode::Parameter> parameters, LexicalEnvironment* parent_environment);
ScriptFunction(const FlyString& name, const Statement& body, Vector<FlyString> parameters, LexicalEnvironment* parent_environment, Object& prototype);
ScriptFunction(const FlyString& name, const Statement& body, Vector<FunctionNode::Parameter> parameters, LexicalEnvironment* parent_environment, Object& prototype);
virtual ~ScriptFunction();
const Statement& body() const { return m_body; }
const Vector<FlyString>& parameters() const { return m_parameters; };
const Vector<FunctionNode::Parameter>& parameters() const { return m_parameters; };
virtual Value call(Interpreter&) override;
virtual Value construct(Interpreter&) override;
@ -56,7 +57,7 @@ private:
FlyString m_name;
NonnullRefPtr<Statement> m_body;
const Vector<FlyString> m_parameters;
const Vector<FunctionNode::Parameter> m_parameters;
LexicalEnvironment* m_parent_environment { nullptr };
};