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Make `Array.prototype.concat` spec compliant (#1353)

pull/1452/head
neeldug 3 years ago committed by GitHub
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  1. 102
      boa/src/builtins/array/mod.rs
  2. 1
      test_ignore.txt

102
boa/src/builtins/array/mod.rs

@ -284,6 +284,30 @@ impl Array {
Ok(array_obj_ptr)
}
/// Utility function for concatenating array objects.
///
/// Returns a Boolean valued property that if `true` indicates that
/// an object should be flattened to its array elements
/// by `Array.prototype.concat`.
fn is_concat_spreadable(this: &Value, context: &mut Context) -> Result<bool> {
// 1. If Type(O) is not Object, return false.
if !this.is_object() {
return Ok(false);
}
// 2. Let spreadable be ? Get(O, @@isConcatSpreadable).
let spreadable = this.get_field(WellKnownSymbols::is_concat_spreadable(), context)?;
// 3. If spreadable is not undefined, return ! ToBoolean(spreadable).
if !spreadable.is_undefined() {
return Ok(spreadable.to_boolean());
}
// 4. Return ? IsArray(O).
match this.as_object() {
Some(obj) => Ok(obj.is_array()),
_ => Ok(false),
}
}
/// `get Array [ @@species ]`
///
/// The `Array [ @@species ]` accessor property returns the Array constructor.
@ -459,30 +483,66 @@ impl Array {
/// [spec]: https://tc39.es/ecma262/#sec-array.prototype.concat
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat
pub(crate) fn concat(this: &Value, args: &[Value], context: &mut Context) -> Result<Value> {
if args.is_empty() {
// If concat is called with no arguments, it returns the original array
return Ok(this.clone());
}
// Make a new array (using this object as the prototype basis for the new
// one)
let mut new_values: Vec<Value> = Vec::new();
let this_length = this.get_field("length", context)?.to_length(context)?;
for n in 0..this_length {
new_values.push(this.get_field(n, context)?);
}
for concat_array in args {
let concat_length = concat_array
.get_field("length", context)?
.to_length(context)?;
for n in 0..concat_length {
new_values.push(concat_array.get_field(n, context)?);
// 1. Let O be ? ToObject(this value).
let obj = this.to_object(context)?;
// 2. Let A be ? ArraySpeciesCreate(O, 0).
let arr = Self::array_species_create(&obj, 0, context)?;
// 3. Let n be 0.
let mut n = 0;
// 4. Prepend O to items.
// 5. For each element E of items, do
for item in [Value::from(obj)].iter().chain(args.iter()) {
// a. Let spreadable be ? IsConcatSpreadable(E).
let spreadable = Self::is_concat_spreadable(&item, context)?;
// b. If spreadable is true, then
if spreadable {
// item is guaranteed to be an object since is_concat_spreadable checks it,
// so we can call `.unwrap()`
let item = item.as_object().unwrap();
// i. Let k be 0.
// ii. Let len be ? LengthOfArrayLike(E).
let len = item.length_of_array_like(context)?;
// iii. If n + len > 2^53 - 1, throw a TypeError exception.
if n + len > Number::MAX_SAFE_INTEGER as usize {
return context.throw_type_error(
"length + number of arguments exceeds the max safe integer limit",
);
}
// iv. Repeat, while k < len,
for k in 0..len {
// 1. Let P be ! ToString(𝔽(k)).
// 2. Let exists be ? HasProperty(E, P).
let exists = item.has_property(k, context)?;
// 3. If exists is true, then
if exists {
// a. Let subElement be ? Get(E, P).
let sub_element = item.get(k, context)?;
// b. Perform ? CreateDataPropertyOrThrow(A, ! ToString(𝔽(n)), subElement).
arr.create_data_property_or_throw(n, sub_element, context)?;
}
// 4. Set n to n + 1.
n += 1;
// 5. Set k to k + 1.
}
}
// c. Else,
else {
// i. NOTE: E is added as a single item rather than spread.
// ii. If n ≥ 253 - 1, throw a TypeError exception.
if n >= Number::MAX_SAFE_INTEGER as usize {
return context.throw_type_error("length exceeds the max safe integer limit");
}
// iii. Perform ? CreateDataPropertyOrThrow(A, ! ToString(𝔽(n)), E).
arr.create_data_property_or_throw(n, item, context)?;
// iv. Set n to n + 1.
n += 1
}
}
// 6. Perform ? Set(A, "length", 𝔽(n), true).
arr.set("length", n, true, context)?;
Self::construct_array(this, &new_values, context)
// 7. Return A.
Ok(Value::from(arr))
}
/// `Array.prototype.push( ...items )`

1
test_ignore.txt

@ -10,7 +10,6 @@ feature:json-modules
//feature:class
// These seem to run forever:
arg-length-exceeding-integer-limit
// These generate a stack overflow
tco-call

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