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//! This module implements the `JsObject` structure.
//!
//! The `JsObject` is a garbage collected Object.
use super::{NativeObject, Object, PROTOTYPE};
use crate::{
builtins::function::{
create_unmapped_arguments_object, Captures, ClosureFunction, Function, NativeFunction,
},
environment::{
environment_record_trait::EnvironmentRecordTrait,
function_environment_record::{BindingStatus, FunctionEnvironmentRecord},
lexical_environment::Environment,
},
exec::InterpreterState,
object::{ObjectData, ObjectKind},
property::{PropertyDescriptor, PropertyKey},
syntax::ast::node::RcStatementList,
value::PreferredType,
Context, Executable, JsResult, JsValue,
};
use gc::{Finalize, Gc, GcCell, GcCellRef, GcCellRefMut, Trace};
use std::{
cell::RefCell,
collections::HashMap,
error::Error,
fmt::{self, Debug, Display},
result::Result as StdResult,
};
/// A wrapper type for an immutably borrowed type T.
pub type Ref<'a, T> = GcCellRef<'a, T>;
/// A wrapper type for a mutably borrowed type T.
pub type RefMut<'a, T, U> = GcCellRefMut<'a, T, U>;
/// Garbage collected `Object`.
#[derive(Trace, Finalize, Clone, Default)]
pub struct JsObject(Gc<GcCell<Object>>);
/// The body of a JavaScript function.
///
/// This is needed for the call method since we cannot mutate the function itself since we
/// already borrow it so we get the function body clone it then drop the borrow and run the body
enum FunctionBody {
BuiltInFunction(NativeFunction),
BuiltInConstructor(NativeFunction),
Closure {
function: Box<dyn ClosureFunction>,
captures: Captures,
},
Ordinary(RcStatementList),
}
impl JsObject {
/// Create a new `GcObject` from a `Object`.
#[inline]
pub fn new(object: Object) -> Self {
Self(Gc::new(GcCell::new(object)))
}
/// Immutably borrows the `Object`.
///
/// The borrow lasts until the returned `Ref` exits scope.
/// Multiple immutable borrows can be taken out at the same time.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn borrow(&self) -> Ref<'_, Object> {
self.try_borrow().expect("Object already mutably borrowed")
}
/// Mutably borrows the Object.
///
/// The borrow lasts until the returned `RefMut` exits scope.
/// The object cannot be borrowed while this borrow is active.
///
///# Panics
/// Panics if the object is currently borrowed.
#[inline]
#[track_caller]
pub fn borrow_mut(&self) -> RefMut<'_, Object, Object> {
self.try_borrow_mut().expect("Object already borrowed")
}
/// Immutably borrows the `Object`, returning an error if the value is currently mutably borrowed.
///
/// The borrow lasts until the returned `GcCellRef` exits scope.
/// Multiple immutable borrows can be taken out at the same time.
///
/// This is the non-panicking variant of [`borrow`](#method.borrow).
#[inline]
pub fn try_borrow(&self) -> StdResult<Ref<'_, Object>, BorrowError> {
self.0.try_borrow().map_err(|_| BorrowError)
}
/// Mutably borrows the object, returning an error if the value is currently borrowed.
///
/// The borrow lasts until the returned `GcCellRefMut` exits scope.
/// The object be borrowed while this borrow is active.
///
/// This is the non-panicking variant of [`borrow_mut`](#method.borrow_mut).
#[inline]
pub fn try_borrow_mut(&self) -> StdResult<RefMut<'_, Object, Object>, BorrowMutError> {
self.0.try_borrow_mut().map_err(|_| BorrowMutError)
}
/// Checks if the garbage collected memory is the same.
#[inline]
pub fn equals(lhs: &Self, rhs: &Self) -> bool {
std::ptr::eq(lhs.as_ref(), rhs.as_ref())
}
/// Internal implementation of [`call`](#method.call) and [`construct`](#method.construct).
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
///
/// <https://tc39.es/ecma262/#sec-prepareforordinarycall>
/// <https://tc39.es/ecma262/#sec-ordinarycallbindthis>
/// <https://tc39.es/ecma262/#sec-runtime-semantics-evaluatebody>
/// <https://tc39.es/ecma262/#sec-ordinarycallevaluatebody>
#[track_caller]
pub(super) fn call_construct(
&self,
this_target: &JsValue,
args: &[JsValue],
context: &mut Context,
construct: bool,
) -> JsResult<JsValue> {
let this_function_object = self.clone();
let mut has_parameter_expressions = false;
let body = if let Some(function) = self.borrow().as_function() {
if construct && !function.is_constructable() {
let name = self
.__get__(&"name".into(), self.clone().into(), context)?
.display()
.to_string();
return context.throw_type_error(format!("{} is not a constructor", name));
} else {
match function {
Function::Native {
function,
constructable,
} => {
if *constructable || construct {
FunctionBody::BuiltInConstructor(function.0)
} else {
FunctionBody::BuiltInFunction(function.0)
}
}
Function::Closure {
function, captures, ..
} => FunctionBody::Closure {
function: function.clone(),
captures: captures.clone(),
},
Function::Ordinary {
body,
params,
environment,
flags,
} => {
let this = if construct {
// If the prototype of the constructor is not an object, then use the default object
// prototype as prototype for the new object
// see <https://tc39.es/ecma262/#sec-ordinarycreatefromconstructor>
// see <https://tc39.es/ecma262/#sec-getprototypefromconstructor>
let proto = this_target.as_object().unwrap().__get__(
&PROTOTYPE.into(),
this_target.clone(),
context,
)?;
let proto = if proto.is_object() {
proto
} else {
context
.standard_objects()
.object_object()
.prototype()
.into()
};
JsValue::new(Object::create(proto))
} else {
this_target.clone()
};
// Create a new Function environment whose parent is set to the scope of the function declaration (self.environment)
// <https://tc39.es/ecma262/#sec-prepareforordinarycall>
let local_env = FunctionEnvironmentRecord::new(
this_function_object.clone(),
if construct || !flags.is_lexical_this_mode() {
Some(this.clone())
} else {
None
},
Some(environment.clone()),
// Arrow functions do not have a this binding https://tc39.es/ecma262/#sec-function-environment-records
if flags.is_lexical_this_mode() {
BindingStatus::Lexical
} else {
BindingStatus::Uninitialized
},
JsValue::undefined(),
context,
)?;
let mut arguments_in_parameter_names = false;
for param in params.iter() {
has_parameter_expressions =
has_parameter_expressions || param.init().is_some();
arguments_in_parameter_names =
arguments_in_parameter_names || param.name() == "arguments";
}
// An arguments object is added when all of the following conditions are met
// - If not in an arrow function (10.2.11.16)
// - If the parameter list does not contain `arguments` (10.2.11.17)
// - If there are default parameters or if lexical names and function names do not contain `arguments` (10.2.11.18)
//
// https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
if !flags.is_lexical_this_mode()
&& !arguments_in_parameter_names
&& (has_parameter_expressions
|| (!body.lexically_declared_names().contains("arguments")
&& !body.function_declared_names().contains("arguments")))
{
// Add arguments object
let arguments_obj = create_unmapped_arguments_object(args, context)?;
local_env.create_mutable_binding("arguments", false, true, context)?;
local_env.initialize_binding("arguments", arguments_obj, context)?;
}
// Turn local_env into Environment so it can be cloned
let local_env: Environment = local_env.into();
// Push the environment first so that it will be used by default parameters
context.push_environment(local_env.clone());
// Add argument bindings to the function environment
for (i, param) in params.iter().enumerate() {
// Rest Parameters
if param.is_rest_param() {
function.add_rest_param(param, i, args, context, &local_env);
break;
}
let value = match args.get(i).cloned() {
None | Some(JsValue::Undefined) => param
.init()
.map(|init| init.run(context).ok())
.flatten()
.unwrap_or_default(),
Some(value) => value,
};
function
.add_arguments_to_environment(param, value, &local_env, context);
}
if has_parameter_expressions {
// Create a second environment when default parameter expressions are used
// This prevents variables declared in the function body from being
// used in default parameter initializers.
// https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
let second_env = FunctionEnvironmentRecord::new(
this_function_object,
if construct || !flags.is_lexical_this_mode() {
Some(this)
} else {
None
},
Some(local_env),
// Arrow functions do not have a this binding https://tc39.es/ecma262/#sec-function-environment-records
if flags.is_lexical_this_mode() {
BindingStatus::Lexical
} else {
BindingStatus::Uninitialized
},
JsValue::undefined(),
context,
)?;
context.push_environment(second_env);
}
FunctionBody::Ordinary(body.clone())
}
}
}
} else {
return context.throw_type_error("not a function");
};
match body {
FunctionBody::BuiltInConstructor(function) if construct => {
function(this_target, args, context)
}
FunctionBody::BuiltInConstructor(function) => {
function(&JsValue::undefined(), args, context)
}
FunctionBody::BuiltInFunction(function) => function(this_target, args, context),
FunctionBody::Closure { function, captures } => {
(function)(this_target, args, context, captures)
}
FunctionBody::Ordinary(body) => {
let result = body.run(context);
let this = context.get_this_binding();
if has_parameter_expressions {
context.pop_environment();
}
context.pop_environment();
if construct {
// https://tc39.es/ecma262/#sec-ecmascript-function-objects-construct-argumentslist-newtarget
// 12. If result.[[Type]] is return, then
if context.executor().get_current_state() == &InterpreterState::Return {
// a. If Type(result.[[Value]]) is Object, return NormalCompletion(result.[[Value]]).
if let Ok(v) = &result {
if v.is_object() {
return result;
}
}
}
// 13. Else, ReturnIfAbrupt(result).
result?;
// 14. Return ? constructorEnv.GetThisBinding().
this
} else if context.executor().get_current_state() == &InterpreterState::Return {
result
} else {
result?;
Ok(JsValue::undefined())
}
}
}
}
/// Converts an object to a primitive.
///
/// Diverges from the spec to prevent a stack overflow when the object is recursive.
/// For example,
/// ```javascript
/// let a = [1];
/// a[1] = a;
/// console.log(a.toString()); // We print "1,"
/// ```
/// The spec doesn't mention what to do in this situation, but a naive implementation
/// would overflow the stack recursively calling `toString()`. We follow v8 and SpiderMonkey
/// instead by returning a default value for the given `hint` -- either `0.` or `""`.
/// Example in v8: <https://repl.it/repls/IvoryCircularCertification#index.js>
///
/// More information:
/// - [ECMAScript][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-ordinarytoprimitive
pub(crate) fn ordinary_to_primitive(
&self,
context: &mut Context,
hint: PreferredType,
) -> JsResult<JsValue> {
// 1. Assert: Type(O) is Object.
// Already is JsObject by type.
// 2. Assert: Type(hint) is String and its value is either "string" or "number".
debug_assert!(hint == PreferredType::String || hint == PreferredType::Number);
// Diverge from the spec here to make sure we aren't going to overflow the stack by converting
// a recursive structure
// We can follow v8 & SpiderMonkey's lead and return a default value for the hint in this situation
// (see https://repl.it/repls/IvoryCircularCertification#index.js)
let recursion_limiter = RecursionLimiter::new(self);
if recursion_limiter.live {
// we're in a recursive object, bail
return Ok(match hint {
PreferredType::Number => JsValue::new(0),
PreferredType::String => JsValue::new(""),
PreferredType::Default => unreachable!("checked type hint in step 2"),
});
}
// 3. If hint is "string", then
// a. Let methodNames be « "toString", "valueOf" ».
// 4. Else,
// a. Let methodNames be « "valueOf", "toString" ».
let method_names = if hint == PreferredType::String {
["toString", "valueOf"]
} else {
["valueOf", "toString"]
};
// 5. For each name in methodNames in List order, do
let this = JsValue::new(self.clone());
for name in &method_names {
// a. Let method be ? Get(O, name).
let method: JsValue = this.get_field(*name, context)?;
// b. If IsCallable(method) is true, then
if method.is_function() {
// i. Let result be ? Call(method, O).
let result = context.call(&method, &this, &[])?;
// ii. If Type(result) is not Object, return result.
if !result.is_object() {
return Ok(result);
}
}
}
// 6. Throw a TypeError exception.
context.throw_type_error("cannot convert object to primitive value")
}
/// Return `true` if it is a native object and the native type is `T`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is<T>(&self) -> bool
where
T: NativeObject,
{
self.borrow().is::<T>()
}
/// Downcast a reference to the object,
/// if the object is type native object type `T`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn downcast_ref<T>(&self) -> Option<Ref<'_, T>>
where
T: NativeObject,
{
let object = self.borrow();
if object.is::<T>() {
Some(Ref::map(object, |x| x.downcast_ref::<T>().unwrap()))
} else {
None
}
}
/// Downcast a mutable reference to the object,
/// if the object is type native object type `T`.
///
/// # Panics
///
/// Panics if the object is currently borrowed.
#[inline]
#[track_caller]
pub fn downcast_mut<T>(&mut self) -> Option<RefMut<'_, Object, T>>
where
T: NativeObject,
{
let object = self.borrow_mut();
if object.is::<T>() {
Some(RefMut::map(object, |x| x.downcast_mut::<T>().unwrap()))
} else {
None
}
}
/// Get the prototype of the object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn prototype_instance(&self) -> JsValue {
self.borrow().prototype_instance().clone()
}
/// Set the prototype of the object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed
/// or if th prototype is not an object or undefined.
#[inline]
#[track_caller]
pub fn set_prototype_instance(&self, prototype: JsValue) -> bool {
self.borrow_mut().set_prototype_instance(prototype)
}
/// Checks if it an `Array` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_array(&self) -> bool {
self.borrow().is_array()
}
/// Checks if it is an `ArrayIterator` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_array_iterator(&self) -> bool {
self.borrow().is_array_iterator()
}
/// Checks if it is a `Map` object.pub
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_map(&self) -> bool {
self.borrow().is_map()
}
/// Checks if it a `String` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_string(&self) -> bool {
self.borrow().is_string()
}
/// Checks if it a `Function` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_function(&self) -> bool {
self.borrow().is_function()
}
/// Checks if it a Symbol object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_symbol(&self) -> bool {
self.borrow().is_symbol()
}
/// Checks if it an Error object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_error(&self) -> bool {
self.borrow().is_error()
}
/// Checks if it a Boolean object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_boolean(&self) -> bool {
self.borrow().is_boolean()
}
/// Checks if it a `Number` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_number(&self) -> bool {
self.borrow().is_number()
}
/// Checks if it a `BigInt` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_bigint(&self) -> bool {
self.borrow().is_bigint()
}
/// Checks if it a `RegExp` object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_regexp(&self) -> bool {
self.borrow().is_regexp()
}
/// Checks if it an ordinary object.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_ordinary(&self) -> bool {
self.borrow().is_ordinary()
}
/// Returns `true` if it holds an Rust type that implements `NativeObject`.
///
/// # Panics
///
/// Panics if the object is currently mutably borrowed.
#[inline]
#[track_caller]
pub fn is_native_object(&self) -> bool {
self.borrow().is_native_object()
}
/// Determines if `value` inherits from the instance object inheritance path.
///
/// More information:
/// - [EcmaScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-ordinaryhasinstance
#[inline]
pub(crate) fn ordinary_has_instance(
&self,
context: &mut Context,
value: &JsValue,
) -> JsResult<bool> {
// 1. If IsCallable(C) is false, return false.
if !self.is_callable() {
return Ok(false);
}
// TODO: 2. If C has a [[BoundTargetFunction]] internal slot, then
// a. Let BC be C.[[BoundTargetFunction]].
// b. Return ? InstanceofOperator(O, BC).
// 3. If Type(O) is not Object, return false.
if let Some(object) = value.as_object() {
// 4. Let P be ? Get(C, "prototype").
// 5. If Type(P) is not Object, throw a TypeError exception.
if let Some(prototype) = self.get("prototype", context)?.as_object() {
// 6. Repeat,
// a. Set O to ? O.[[GetPrototypeOf]]().
// b. If O is null, return false.
let mut object = object.__get_prototype_of__(context)?;
while let Some(object_prototype) = object.as_object() {
// c. If SameValue(P, O) is true, return true.
if JsObject::equals(&prototype, &object_prototype) {
return Ok(true);
}
// a. Set O to ? O.[[GetPrototypeOf]]().
object = object_prototype.__get_prototype_of__(context)?;
}
Ok(false)
} else {
Err(context
.construct_type_error("function has non-object prototype in instanceof check"))
}
} else {
Ok(false)
}
}
pub fn to_property_descriptor(&self, context: &mut Context) -> JsResult<PropertyDescriptor> {
// 1 is implemented on the method `to_property_descriptor` of value
// 2. Let desc be a new Property Descriptor that initially has no fields.
let mut desc = PropertyDescriptor::builder();
// 3. Let hasEnumerable be ? HasProperty(Obj, "enumerable").
// 4. If hasEnumerable is true, then ...
if self.has_property("enumerable", context)? {
// a. Let enumerable be ! ToBoolean(? Get(Obj, "enumerable")).
// b. Set desc.[[Enumerable]] to enumerable.
desc = desc.enumerable(self.get("enumerable", context)?.to_boolean());
}
// 5. Let hasConfigurable be ? HasProperty(Obj, "configurable").
// 6. If hasConfigurable is true, then ...
if self.has_property("configurable", context)? {
// a. Let configurable be ! ToBoolean(? Get(Obj, "configurable")).
// b. Set desc.[[Configurable]] to configurable.
desc = desc.configurable(self.get("configurable", context)?.to_boolean());
}
// 7. Let hasValue be ? HasProperty(Obj, "value").
// 8. If hasValue is true, then ...
if self.has_property("value", context)? {
// a. Let value be ? Get(Obj, "value").
// b. Set desc.[[Value]] to value.
desc = desc.value(self.get("value", context)?);
}
// 9. Let hasWritable be ? HasProperty(Obj, ).
// 10. If hasWritable is true, then ...
if self.has_property("writable", context)? {
// a. Let writable be ! ToBoolean(? Get(Obj, "writable")).
// b. Set desc.[[Writable]] to writable.
desc = desc.writable(self.get("writable", context)?.to_boolean());
}
// 11. Let hasGet be ? HasProperty(Obj, "get").
// 12. If hasGet is true, then
let get = if self.has_property("get", context)? {
// a. Let getter be ? Get(Obj, "get").
let getter = self.get("get", context)?;
// b. If IsCallable(getter) is false and getter is not undefined, throw a TypeError exception.
// todo: extract IsCallable to be callable from Value
if !getter.is_undefined() && getter.as_object().map_or(true, |o| !o.is_callable()) {
return Err(
context.construct_type_error("Property descriptor getter must be callable")
);
}
// c. Set desc.[[Get]] to getter.
Some(getter)
} else {
None
};
// 13. Let hasSet be ? HasProperty(Obj, "set").
// 14. If hasSet is true, then
let set = if self.has_property("set", context)? {
// 14.a. Let setter be ? Get(Obj, "set").
let setter = self.get("set", context)?;
// 14.b. If IsCallable(setter) is false and setter is not undefined, throw a TypeError exception.
// todo: extract IsCallable to be callable from Value
if !setter.is_undefined() && setter.as_object().map_or(true, |o| !o.is_callable()) {
return Err(
context.construct_type_error("Property descriptor setter must be callable")
);
}
// 14.c. Set desc.[[Set]] to setter.
Some(setter)
} else {
None
};
// 15. If desc.[[Get]] is present or desc.[[Set]] is present, then ...
// a. If desc.[[Value]] is present or desc.[[Writable]] is present, throw a TypeError exception.
if get.as_ref().or_else(|| set.as_ref()).is_some() && desc.inner().is_data_descriptor() {
return Err(context.construct_type_error(
"Invalid property descriptor.\
Cannot both specify accessors and a value or writable attribute",
));
}
desc = desc.maybe_get(get).maybe_set(set);
// 16. Return desc.
Ok(desc.build())
}
/// `7.3.25 CopyDataProperties ( target, source, excludedItems )`
///
/// More information:
/// - [ECMAScript][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-copydataproperties
#[inline]
pub fn copy_data_properties<K>(
&mut self,
source: &JsValue,
excluded_keys: Vec<K>,
context: &mut Context,
) -> JsResult<()>
where
K: Into<PropertyKey>,
{
// 1. Assert: Type(target) is Object.
// 2. Assert: excludedItems is a List of property keys.
// 3. If source is undefined or null, return target.
if source.is_null_or_undefined() {
return Ok(());
}
// 4. Let from be ! ToObject(source).
let from = source
.to_object(context)
.expect("function ToObject should never complete abruptly here");
// 5. Let keys be ? from.[[OwnPropertyKeys]]().
// 6. For each element nextKey of keys, do
let excluded_keys: Vec<PropertyKey> = excluded_keys.into_iter().map(|e| e.into()).collect();
for key in from.__own_property_keys__(context)? {
// a. Let excluded be false.
let mut excluded = false;
// b. For each element e of excludedItems, do
for e in &excluded_keys {
// i. If SameValue(e, nextKey) is true, then
if *e == key {
// 1. Set excluded to true.
excluded = true;
break;
}
}
// c. If excluded is false, then
if !excluded {
// i. Let desc be ? from.[[GetOwnProperty]](nextKey).
let desc = from.__get_own_property__(&key, context)?;
// ii. If desc is not undefined and desc.[[Enumerable]] is true, then
if let Some(desc) = desc {
if let Some(enumerable) = desc.enumerable() {
if enumerable {
// 1. Let propValue be ? Get(from, nextKey).
let prop_value = from.__get__(&key, from.clone().into(), context)?;
// 2. Perform ! CreateDataPropertyOrThrow(target, nextKey, propValue).
self.create_data_property_or_throw(key, prop_value, context)
.expect(
"CreateDataPropertyOrThrow should never complete abruptly here",
);
}
}
}
}
}
// 7. Return target.
Ok(())
}
/// Helper function for property insertion.
#[inline]
#[track_caller]
pub(crate) fn insert<K, P>(&self, key: K, property: P) -> Option<PropertyDescriptor>
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.borrow_mut().insert(key, property)
}
/// Inserts a field in the object `properties` without checking if it's writable.
///
/// If a field was already in the object with the same name that a `Some` is returned
/// with that field, otherwise None is returned.
#[inline]
pub fn insert_property<K, P>(&self, key: K, property: P) -> Option<PropertyDescriptor>
where
K: Into<PropertyKey>,
P: Into<PropertyDescriptor>,
{
self.insert(key.into(), property)
}
/// It determines if Object is a callable function with a `[[Call]]` internal method.
///
/// More information:
/// - [EcmaScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iscallable
#[inline]
#[track_caller]
pub fn is_callable(&self) -> bool {
self.borrow().is_callable()
}
/// It determines if Object is a function object with a `[[Construct]]` internal method.
///
/// More information:
/// - [EcmaScript reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-isconstructor
#[inline]
#[track_caller]
pub fn is_constructable(&self) -> bool {
self.borrow().is_constructable()
}
/// Returns true if the GcObject is the global for a Realm
pub fn is_global(&self) -> bool {
matches!(
self.borrow().data,
ObjectData {
kind: ObjectKind::Global,
..
}
)
}
}
impl AsRef<GcCell<Object>> for JsObject {
#[inline]
fn as_ref(&self) -> &GcCell<Object> {
&*self.0
}
}
/// An error returned by [`JsObject::try_borrow`](struct.JsObject.html#method.try_borrow).
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct BorrowError;
impl Display for BorrowError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Display::fmt("Object already mutably borrowed", f)
}
}
impl Error for BorrowError {}
/// An error returned by [`JsObject::try_borrow_mut`](struct.JsObject.html#method.try_borrow_mut).
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct BorrowMutError;
impl Display for BorrowMutError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Display::fmt("Object already borrowed", f)
}
}
impl Error for BorrowMutError {}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
enum RecursionValueState {
/// This value is "live": there's an active RecursionLimiter that hasn't been dropped.
Live,
/// This value has been seen before, but the recursion limiter has been dropped.
/// For example:
/// ```javascript
/// let b = [];
/// JSON.stringify([ // Create a recursion limiter for the root here
/// b, // state for b's &JsObject here is None
/// b, // state for b's &JsObject here is Visited
/// ]);
/// ```
Visited,
}
/// Prevents infinite recursion during `Debug::fmt`, `JSON.stringify`, and other conversions.
/// This uses a thread local, so is not safe to use where the object graph will be traversed by
/// multiple threads!
#[derive(Debug)]
pub struct RecursionLimiter {
/// If this was the first `JsObject` in the tree.
top_level: bool,
/// The ptr being kept in the HashSet, so we can delete it when we drop.
ptr: usize,
/// If this JsObject has been visited before in the graph, but not in the current branch.
pub visited: bool,
/// If this JsObject has been visited in the current branch of the graph.
pub live: bool,
}
impl Drop for RecursionLimiter {
fn drop(&mut self) {
if self.top_level {
// When the top level of the graph is dropped, we can free the entire map for the next traversal.
Self::SEEN.with(|hm| hm.borrow_mut().clear());
} else if !self.live {
// This was the first RL for this object to become live, so it's no longer live now that it's dropped.
Self::SEEN.with(|hm| {
hm.borrow_mut()
.insert(self.ptr, RecursionValueState::Visited)
});
}
}
}
impl RecursionLimiter {
thread_local! {
/// The map of pointers to `JsObject` that have been visited during the current `Debug::fmt` graph,
/// and the current state of their RecursionLimiter (dropped or live -- see `RecursionValueState`)
static SEEN: RefCell<HashMap<usize, RecursionValueState>> = RefCell::new(HashMap::new());
}
/// Determines if the specified `JsObject` has been visited, and returns a struct that will free it when dropped.
///
/// This is done by maintaining a thread-local hashset containing the pointers of `JsObject` values that have been
/// visited. The first `JsObject` visited will clear the hashset, while any others will check if they are contained
/// by the hashset.
pub fn new(o: &JsObject) -> Self {
// We shouldn't have to worry too much about this being moved during Debug::fmt.
let ptr = (o.as_ref() as *const _) as usize;
let (top_level, visited, live) = Self::SEEN.with(|hm| {
let mut hm = hm.borrow_mut();
let top_level = hm.is_empty();
let old_state = hm.insert(ptr, RecursionValueState::Live);
(
top_level,
old_state == Some(RecursionValueState::Visited),
old_state == Some(RecursionValueState::Live),
)
});
Self {
top_level,
ptr,
visited,
live,
}
}
}
impl Debug for JsObject {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> std::fmt::Result {
let limiter = RecursionLimiter::new(self);
// Typically, using `!limiter.live` would be good enough here.
// However, the JS object hierarchy involves quite a bit of repitition, and the sheer amount of data makes
// understanding the Debug output impossible; limiting the usefulness of it.
//
// Instead, we check if the object has appeared before in the entire graph. This means that objects will appear
// at most once, hopefully making things a bit clearer.
if !limiter.visited && !limiter.live {
f.debug_tuple("JsObject").field(&self.0).finish()
} else {
f.write_str("{ ... }")
}
}
}