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//! Boa's implementation of ECMAScript's `IteratorRecord` and iterator prototype objects.
use crate::{
builtins::{BuiltInBuilder, IntrinsicObject},
context::intrinsics::Intrinsics,
error::JsNativeError,
js_string,
object::JsObject,
realm::Realm,
symbol::JsSymbol,
Context, JsResult, JsValue,
};
use boa_gc::{Finalize, Trace};
use boa_profiler::Profiler;
mod async_from_sync_iterator;
pub(crate) use async_from_sync_iterator::AsyncFromSyncIterator;
/// `IfAbruptCloseIterator ( value, iteratorRecord )`
///
/// `IfAbruptCloseIterator` is a shorthand for a sequence of algorithm steps that use an `Iterator`
/// Record.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-ifabruptcloseiterator
macro_rules! if_abrupt_close_iterator {
($value:expr, $iterator_record:expr, $context:expr) => {
match $value {
// 1. If value is an abrupt completion, return ? IteratorClose(iteratorRecord, value).
Err(err) => return $iterator_record.close(Err(err), $context),
// 2. Else if value is a Completion Record, set value to value.
Ok(value) => value,
}
};
}
// Export macro to crate level
pub(crate) use if_abrupt_close_iterator;
use super::OrdinaryObject;
/// The built-in iterator prototypes.
#[derive(Debug, Default, Trace, Finalize)]
pub struct IteratorPrototypes {
/// The `IteratorPrototype` object.
iterator: JsObject,
/// The `AsyncIteratorPrototype` object.
async_iterator: JsObject,
/// The `AsyncFromSyncIteratorPrototype` prototype object.
async_from_sync_iterator: JsObject,
/// The `ArrayIteratorPrototype` prototype object.
array: JsObject,
/// The `SetIteratorPrototype` prototype object.
set: JsObject,
/// The `StringIteratorPrototype` prototype object.
string: JsObject,
/// The `RegExpStringIteratorPrototype` prototype object.
regexp_string: JsObject,
/// The `MapIteratorPrototype` prototype object.
map: JsObject,
/// The `ForInIteratorPrototype` prototype object.
for_in: JsObject,
/// The `%SegmentIteratorPrototype%` prototype object.
#[cfg(feature = "intl")]
segment: JsObject,
}
impl IteratorPrototypes {
/// Returns the `ArrayIteratorPrototype` object.
#[inline]
#[must_use]
pub fn array(&self) -> JsObject {
self.array.clone()
}
/// Returns the `IteratorPrototype` object.
#[inline]
#[must_use]
pub fn iterator(&self) -> JsObject {
self.iterator.clone()
}
/// Returns the `AsyncIteratorPrototype` object.
#[inline]
#[must_use]
pub fn async_iterator(&self) -> JsObject {
self.async_iterator.clone()
}
/// Returns the `AsyncFromSyncIteratorPrototype` object.
#[inline]
#[must_use]
pub fn async_from_sync_iterator(&self) -> JsObject {
self.async_from_sync_iterator.clone()
}
/// Returns the `SetIteratorPrototype` object.
#[inline]
#[must_use]
pub fn set(&self) -> JsObject {
self.set.clone()
}
/// Returns the `StringIteratorPrototype` object.
#[inline]
#[must_use]
pub fn string(&self) -> JsObject {
self.string.clone()
}
/// Returns the `RegExpStringIteratorPrototype` object.
#[inline]
#[must_use]
pub fn regexp_string(&self) -> JsObject {
self.regexp_string.clone()
}
/// Returns the `MapIteratorPrototype` object.
#[inline]
#[must_use]
pub fn map(&self) -> JsObject {
self.map.clone()
}
/// Returns the `ForInIteratorPrototype` object.
#[inline]
#[must_use]
pub fn for_in(&self) -> JsObject {
self.for_in.clone()
}
/// Returns the `%SegmentIteratorPrototype%` object.
#[inline]
#[must_use]
#[cfg(feature = "intl")]
pub fn segment(&self) -> JsObject {
self.segment.clone()
}
}
/// `%IteratorPrototype%` object
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-%iteratorprototype%-object
pub(crate) struct Iterator;
impl IntrinsicObject for Iterator {
fn init(realm: &Realm) {
let _timer = Profiler::global().start_event("Iterator Prototype", "init");
BuiltInBuilder::with_intrinsic::<Self>(realm)
.static_method(|v, _, _| Ok(v.clone()), JsSymbol::iterator(), 0)
.build();
}
fn get(intrinsics: &Intrinsics) -> JsObject {
intrinsics.objects().iterator_prototypes().iterator()
}
}
/// `%AsyncIteratorPrototype%` object
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-asynciteratorprototype
pub(crate) struct AsyncIterator;
impl IntrinsicObject for AsyncIterator {
fn init(realm: &Realm) {
let _timer = Profiler::global().start_event("AsyncIteratorPrototype", "init");
BuiltInBuilder::with_intrinsic::<Self>(realm)
.static_method(|v, _, _| Ok(v.clone()), JsSymbol::async_iterator(), 0)
.build();
}
fn get(intrinsics: &Intrinsics) -> JsObject {
intrinsics.objects().iterator_prototypes().async_iterator()
}
}
/// `CreateIterResultObject( value, done )`
///
/// Generates an object supporting the `IteratorResult` interface.
pub fn create_iter_result_object(value: JsValue, done: bool, context: &mut Context) -> JsValue {
let _timer = Profiler::global().start_event("create_iter_result_object", "init");
// 1. Assert: Type(done) is Boolean.
// 2. Let obj be ! OrdinaryObjectCreate(%Object.prototype%).
// 3. Perform ! CreateDataPropertyOrThrow(obj, "value", value).
// 4. Perform ! CreateDataPropertyOrThrow(obj, "done", done).
let obj = context
.intrinsics()
.templates()
.iterator_result()
.create(OrdinaryObject, vec![value, done.into()]);
// 5. Return obj.
obj.into()
}
/// Iterator hint for `GetIterator`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IteratorHint {
/// Hints that the iterator should be sync.
Sync,
/// Hints that the iterator should be async.
Async,
}
impl JsValue {
/// `GetIterator ( obj [ , hint [ , method ] ] )`
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-getiterator
pub fn get_iterator(
&self,
context: &mut Context,
hint: Option<IteratorHint>,
method: Option<JsObject>,
) -> JsResult<IteratorRecord> {
// 1. If hint is not present, set hint to sync.
let hint = hint.unwrap_or(IteratorHint::Sync);
// 2. If method is not present, then
let method = if method.is_some() {
method
} else {
// a. If hint is async, then
if hint == IteratorHint::Async {
// i. Set method to ? GetMethod(obj, @@asyncIterator).
if let Some(method) = self.get_method(JsSymbol::async_iterator(), context)? {
Some(method)
} else {
// ii. If method is undefined, then
// 1. Let syncMethod be ? GetMethod(obj, @@iterator).
let sync_method = self.get_method(JsSymbol::iterator(), context)?;
// 2. Let syncIteratorRecord be ? GetIterator(obj, sync, syncMethod).
let sync_iterator_record =
self.get_iterator(context, Some(IteratorHint::Sync), sync_method)?;
// 3. Return ! CreateAsyncFromSyncIterator(syncIteratorRecord).
return Ok(AsyncFromSyncIterator::create(sync_iterator_record, context));
}
} else {
// b. Otherwise, set method to ? GetMethod(obj, @@iterator).
self.get_method(JsSymbol::iterator(), context)?
}
}
.ok_or_else(|| {
JsNativeError::typ().with_message(format!(
"value with type `{}` is not iterable",
self.type_of()
))
})?;
// 3. Let iterator be ? Call(method, obj).
let iterator = method.call(self, &[], context)?;
// 4. If Type(iterator) is not Object, throw a TypeError exception.
let iterator_obj = iterator.as_object().ok_or_else(|| {
JsNativeError::typ().with_message("returned iterator is not an object")
})?;
// 5. Let nextMethod be ? GetV(iterator, "next").
let next_method = iterator.get_v(js_string!("next"), context)?;
// 6. Let iteratorRecord be the Record { [[Iterator]]: iterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
// 7. Return iteratorRecord.
Ok(IteratorRecord::new(iterator_obj.clone(), next_method))
}
}
/// The result of the iteration process.
#[derive(Debug, Clone, Trace, Finalize)]
pub struct IteratorResult {
object: JsObject,
}
impl IteratorResult {
/// Gets a new `IteratorResult` from a value. Returns `Err` if
/// the value is not a [`JsObject`]
pub(crate) fn from_value(value: JsValue) -> JsResult<Self> {
if let JsValue::Object(o) = value {
Ok(Self { object: o })
} else {
Err(JsNativeError::typ()
.with_message("next value should be an object")
.into())
}
}
/// Gets the inner object of this `IteratorResult`.
pub(crate) const fn object(&self) -> &JsObject {
&self.object
}
/// `IteratorComplete ( iterResult )`
///
/// The abstract operation `IteratorComplete` takes argument `iterResult` (an `Object`) and
/// returns either a normal completion containing a `Boolean` or a throw completion.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iteratorcomplete
#[inline]
pub fn complete(&self, context: &mut Context) -> JsResult<bool> {
// 1. Return ToBoolean(? Get(iterResult, "done")).
Ok(self.object.get(js_string!("done"), context)?.to_boolean())
}
/// `IteratorValue ( iterResult )`
///
/// The abstract operation `IteratorValue` takes argument `iterResult` (an `Object`) and
/// returns either a normal completion containing an ECMAScript language value or a throw
/// completion.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iteratorvalue
#[inline]
pub fn value(&self, context: &mut Context) -> JsResult<JsValue> {
// 1. Return ? Get(iterResult, "value").
self.object.get(js_string!("value"), context)
}
}
/// Iterator Record
///
/// An Iterator Record is a Record value used to encapsulate an
/// `Iterator` or `AsyncIterator` along with the `next` method.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iterator-records
#[derive(Clone, Debug, Finalize, Trace)]
pub struct IteratorRecord {
/// `[[Iterator]]`
///
/// An object that conforms to the `Iterator` or `AsyncIterator` interface.
iterator: JsObject,
/// `[[NextMethod]]`
///
/// The `next` method of the `[[Iterator]]` object.
next_method: JsValue,
/// `[[Done]]`
///
/// Whether the iterator has been closed.
done: bool,
/// The result of the last call to `next`.
last_result: IteratorResult,
}
impl IteratorRecord {
/// Creates a new `IteratorRecord` with the given iterator object, next method and `done` flag.
#[inline]
#[must_use]
pub fn new(iterator: JsObject, next_method: JsValue) -> Self {
Self {
iterator,
next_method,
done: false,
last_result: IteratorResult {
object: JsObject::with_null_proto(),
},
}
}
/// Get the `[[Iterator]]` field of the `IteratorRecord`.
pub(crate) const fn iterator(&self) -> &JsObject {
&self.iterator
}
/// Gets the `[[NextMethod]]` field of the `IteratorRecord`.
pub(crate) const fn next_method(&self) -> &JsValue {
&self.next_method
}
/// Gets the last result object of the iterator record.
pub(crate) const fn last_result(&self) -> &IteratorResult {
&self.last_result
}
/// Runs `f`, setting the `done` field of this `IteratorRecord` to `true` if `f` returns
/// an error.
fn set_done_on_err<R, F>(&mut self, f: F) -> JsResult<R>
where
F: FnOnce(&mut Self) -> JsResult<R>,
{
let result = f(self);
if result.is_err() {
self.done = true;
}
result
}
/// Gets the current value of the `IteratorRecord`.
pub(crate) fn value(&mut self, context: &mut Context) -> JsResult<JsValue> {
self.set_done_on_err(|iter| iter.last_result.value(context))
}
/// Get the `[[Done]]` field of the `IteratorRecord`.
pub(crate) const fn done(&self) -> bool {
self.done
}
/// Updates the current result value of this iterator record.
pub(crate) fn update_result(&mut self, result: JsValue, context: &mut Context) -> JsResult<()> {
self.set_done_on_err(|iter| {
// 3. If Type(result) is not Object, throw a TypeError exception.
// 4. Return result.
// `IteratorResult::from_value` does this for us.
// `IteratorStep(iteratorRecord)`
// https://tc39.es/ecma262/#sec-iteratorstep
// 1. Let result be ? IteratorNext(iteratorRecord).
let result = IteratorResult::from_value(result)?;
// 2. Let done be ? IteratorComplete(result).
// 3. If done is true, return false.
iter.done = result.complete(context)?;
iter.last_result = result;
Ok(())
})
}
/// `IteratorNext ( iteratorRecord [ , value ] )`
///
/// The abstract operation `IteratorNext` takes argument `iteratorRecord` (an `Iterator`
/// Record) and optional argument `value` (an ECMAScript language value) and returns either a
/// normal completion containing an `Object` or a throw completion.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iteratornext
pub(crate) fn step_with(
&mut self,
value: Option<&JsValue>,
context: &mut Context,
) -> JsResult<bool> {
let _timer = Profiler::global().start_event("IteratorRecord::step_with", "iterator");
self.set_done_on_err(|iter| {
// 1. If value is not present, then
// a. Let result be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]).
// 2. Else,
// a. Let result be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]], « value »).
let result = iter.next_method.call(
&iter.iterator.clone().into(),
value.map_or(&[], std::slice::from_ref),
context,
)?;
iter.update_result(result, context)?;
// 4. Return result.
Ok(iter.done)
})
}
/// `IteratorStep ( iteratorRecord )`
///
/// Updates the `IteratorRecord` and returns `true` if the next result record returned
/// `done: true`, otherwise returns `false`. This differs slightly from the spec, but also
/// simplifies some logic around iterators.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iteratorstep
pub(crate) fn step(&mut self, context: &mut Context) -> JsResult<bool> {
self.step_with(None, context)
}
/// `IteratorClose ( iteratorRecord, completion )`
///
/// The abstract operation `IteratorClose` takes arguments `iteratorRecord` (an
/// [Iterator Record][Self]) and `completion` (a `Completion` Record) and returns a
/// `Completion` Record. It is used to notify an iterator that it should perform any actions it
/// would normally perform when it has reached its completed state.
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iteratorclose
pub(crate) fn close(
&self,
completion: JsResult<JsValue>,
context: &mut Context,
) -> JsResult<JsValue> {
let _timer = Profiler::global().start_event("IteratorRecord::close", "iterator");
// 1. Assert: Type(iteratorRecord.[[Iterator]]) is Object.
// 2. Let iterator be iteratorRecord.[[Iterator]].
let iterator = &self.iterator;
// 3. Let innerResult be Completion(GetMethod(iterator, "return")).
let inner_result = iterator.get_method(js_string!("return"), context);
// 4. If innerResult.[[Type]] is normal, then
let inner_result = match inner_result {
Ok(inner_result) => {
// a. Let return be innerResult.[[Value]].
let r#return = inner_result;
if let Some(r#return) = r#return {
// c. Set innerResult to Completion(Call(return, iterator)).
r#return.call(&iterator.clone().into(), &[], context)
} else {
// b. If return is undefined, return ? completion.
return completion;
}
}
Err(inner_result) => {
// 5. If completion.[[Type]] is throw, return ? completion.
completion?;
// 6. If innerResult.[[Type]] is throw, return ? innerResult.
return Err(inner_result);
}
};
// 5. If completion.[[Type]] is throw, return ? completion.
let completion = completion?;
// 6. If innerResult.[[Type]] is throw, return ? innerResult.
let inner_result = inner_result?;
if inner_result.is_object() {
// 8. Return ? completion.
Ok(completion)
} else {
// 7. If Type(innerResult.[[Value]]) is not Object, throw a TypeError exception.
Err(JsNativeError::typ()
.with_message("inner result was not an object")
.into())
}
}
}
/// `IterableToList ( items [ , method ] )`
///
/// More information:
/// - [ECMA reference][spec]
///
/// [spec]: https://tc39.es/ecma262/#sec-iterabletolist
pub(crate) fn iterable_to_list(
context: &mut Context,
items: &JsValue,
method: Option<JsObject>,
) -> JsResult<Vec<JsValue>> {
let _timer = Profiler::global().start_event("iterable_to_list", "iterator");
// 1. If method is present, then
// a. Let iteratorRecord be ? GetIterator(items, sync, method).
// 2. Else,
// a. Let iteratorRecord be ? GetIterator(items, sync).
let mut iterator_record = items.get_iterator(context, Some(IteratorHint::Sync), method)?;
// 3. Let values be a new empty List.
let mut values = Vec::new();
// 4. Let next be true.
// 5. Repeat, while next is not false,
// a. Set next to ? IteratorStep(iteratorRecord).
// b. If next is not false, then
// i. Let nextValue be ? IteratorValue(next).
// ii. Append nextValue to the end of the List values.
while !iterator_record.step(context)? {
values.push(iterator_record.value(context)?);
}
// 6. Return values.
Ok(values)
}