Implementation of for...of loops (#704)

* Initial implementation of for...of loop

* Initial implementation of for...of loop

* Extend for...of to support var, let, and const lhs

* Use cached well known symbols

* Nest use statements

* Nest use statements

* Add tests.

* Initial implementation of for...of loop

* Extend for...of to support var, let, and const lhs

* Use cached well known symbols

* Nest use statements

* Nest use statements

* Add tests.

* Add tests, cache iterator prototypes, pull common iterator functions out into their own file to allow for repeated use.

* Initial implementation of for...of loop

* Extend for...of to support var, let, and const lhs

* Use cached well known symbols

* Nest use statements

* Nest use statements

* Add tests.

* Add tests, cache iterator prototypes, pull common iterator functions out into their own file to allow for repeated use.

* Initial implementation of for...of loop

* Extend for...of to support var, let, and const lhs

* Use cached well known symbols

* Initial implementation of for...of loop

* Nest use statements

* Add string iterator

* Clean up merge

* Use ctx.global_iterator()

* Merge upstream

* Use u32 as array next index

* Use into

* Use boa::Result

* Tidy up use statement

* Tidy up use statement

boa/src/builtins/array/array_iterator.rs

@@ -0,0 +1,139 @@
+use crate::{
+    builtins::{function::make_builtin_fn, iterable::create_iter_result_object, Array, Value},
+    object::ObjectData,
+    property::{Attribute, Property},
+    BoaProfiler, Context, Result,
+};
+use gc::{Finalize, Trace};
+
+#[derive(Debug, Clone, Finalize, Trace)]
+pub enum ArrayIterationKind {
+    Key,
+    Value,
+    KeyAndValue,
+}
+
+/// The Array Iterator object represents an iteration over an array. It implements the iterator protocol.
+///
+/// More information:
+///  - [ECMAScript reference][spec]
+///
+/// [spec]: https://tc39.es/ecma262/#sec-array-iterator-objects
+#[derive(Debug, Clone, Finalize, Trace)]
+pub struct ArrayIterator {
+    array: Value,
+    next_index: u32,
+    kind: ArrayIterationKind,
+}
+
+impl ArrayIterator {
+    pub(crate) const NAME: &'static str = "ArrayIterator";
+
+    fn new(array: Value, kind: ArrayIterationKind) -> Self {
+        ArrayIterator {
+            array,
+            kind,
+            next_index: 0,
+        }
+    }
+
+    /// CreateArrayIterator( array, kind )
+    ///
+    /// Creates a new iterator over the given array.
+    ///
+    /// More information:
+    ///  - [ECMA reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-createarrayiterator
+    pub(crate) fn create_array_iterator(
+        ctx: &Context,
+        array: Value,
+        kind: ArrayIterationKind,
+    ) -> Result<Value> {
+        let array_iterator = Value::new_object(Some(ctx.global_object()));
+        array_iterator.set_data(ObjectData::ArrayIterator(Self::new(array, kind)));
+        array_iterator
+            .as_object_mut()
+            .expect("array iterator object")
+            .set_prototype_instance(ctx.iterator_prototypes().array_iterator().into());
+        Ok(array_iterator)
+    }
+
+    /// %ArrayIteratorPrototype%.next( )
+    ///
+    /// Gets the next result in the array.
+    ///
+    /// More information:
+    ///  - [ECMA reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-%arrayiteratorprototype%.next
+    pub(crate) fn next(this: &Value, _args: &[Value], ctx: &mut Context) -> Result<Value> {
+        if let Value::Object(ref object) = this {
+            let mut object = object.borrow_mut();
+            if let Some(array_iterator) = object.as_array_iterator_mut() {
+                let index = array_iterator.next_index;
+                if array_iterator.array.is_undefined() {
+                    return Ok(create_iter_result_object(ctx, Value::undefined(), true));
+                }
+                let len = array_iterator
+                    .array
+                    .get_field("length")
+                    .as_number()
+                    .ok_or_else(|| ctx.construct_type_error("Not an array"))?
+                    as u32;
+                if array_iterator.next_index >= len {
+                    array_iterator.array = Value::undefined();
+                    return Ok(create_iter_result_object(ctx, Value::undefined(), true));
+                }
+                array_iterator.next_index = index + 1;
+                match array_iterator.kind {
+                    ArrayIterationKind::Key => {
+                        Ok(create_iter_result_object(ctx, index.into(), false))
+                    }
+                    ArrayIterationKind::Value => {
+                        let element_value = array_iterator.array.get_field(index);
+                        Ok(create_iter_result_object(ctx, element_value, false))
+                    }
+                    ArrayIterationKind::KeyAndValue => {
+                        let element_value = array_iterator.array.get_field(index);
+                        let result = Array::make_array(
+                            &Value::new_object(Some(ctx.global_object())),
+                            &[index.into(), element_value],
+                            ctx,
+                        )?;
+                        Ok(create_iter_result_object(ctx, result, false))
+                    }
+                }
+            } else {
+                ctx.throw_type_error("`this` is not an ArrayIterator")
+            }
+        } else {
+            ctx.throw_type_error("`this` is not an ArrayIterator")
+        }
+    }
+
+    /// Create the %ArrayIteratorPrototype% object
+    ///
+    /// More information:
+    ///  - [ECMA reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-%arrayiteratorprototype%-object
+    pub(crate) fn create_prototype(ctx: &mut Context, iterator_prototype: Value) -> Value {
+        let global = ctx.global_object();
+        let _timer = BoaProfiler::global().start_event(Self::NAME, "init");
+
+        // Create prototype
+        let array_iterator = Value::new_object(Some(global));
+        make_builtin_fn(Self::next, "next", &array_iterator, 0, ctx);
+        array_iterator
+            .as_object_mut()
+            .expect("array iterator prototype object")
+            .set_prototype_instance(iterator_prototype);
+
+        let to_string_tag = ctx.well_known_symbols().to_string_tag_symbol();
+        let to_string_tag_property =
+            Property::data_descriptor(Value::string("Array Iterator"), Attribute::CONFIGURABLE);
+        array_iterator.set_property(to_string_tag, to_string_tag_property);
+        array_iterator
+    }
+}

boa/src/builtins/array/mod.rs

@@ -9,11 +9,13 @@
 //! [spec]: https://tc39.es/ecma262/#sec-array-objects
 //! [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
 
+pub mod array_iterator;
 #[cfg(test)]
 mod tests;
 
 use super::function::{make_builtin_fn, make_constructor_fn};
 use crate::{
+    builtins::array::array_iterator::{ArrayIterationKind, ArrayIterator},
     object::{ObjectData, PROTOTYPE},
     property::{Attribute, Property},
     value::{same_value_zero, Value},
@@ -1091,6 +1093,60 @@ impl Array {
         Ok(accumulator)
     }
 
+    /// `Array.prototype.values( )`
+    ///
+    /// The values method returns an iterable that iterates over the values in the array.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-array.prototype.values
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/values
+    pub(crate) fn values(
+        this: &Value,
+        _args: &[Value],
+        interpreter: &mut Context,
+    ) -> Result<Value> {
+        ArrayIterator::create_array_iterator(interpreter, this.clone(), ArrayIterationKind::Value)
+    }
+
+    /// `Array.prototype.keys( )`
+    ///
+    /// The keys method returns an iterable that iterates over the indexes in the array.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-array.prototype.values
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/values
+    pub(crate) fn keys(this: &Value, _args: &[Value], interpreter: &mut Context) -> Result<Value> {
+        ArrayIterator::create_array_iterator(interpreter, this.clone(), ArrayIterationKind::Key)
+    }
+
+    /// `Array.prototype.entries( )`
+    ///
+    /// The entries method returns an iterable that iterates over the key-value pairs in the array.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-array.prototype.values
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/values
+    pub(crate) fn entries(
+        this: &Value,
+        _args: &[Value],
+        interpreter: &mut Context,
+    ) -> Result<Value> {
+        ArrayIterator::create_array_iterator(
+            interpreter,
+            this.clone(),
+            ArrayIterationKind::KeyAndValue,
+        )
+    }
+
     /// Initialise the `Array` object on the global object.
     #[inline]
     pub(crate) fn init(interpreter: &mut Context) -> (&'static str, Value) {
@@ -1137,6 +1193,15 @@ impl Array {
             2,
             interpreter,
         );
+        make_builtin_fn(Self::values, "values", &prototype, 0, interpreter);
+        make_builtin_fn(Self::keys, "keys", &prototype, 0, interpreter);
+        make_builtin_fn(Self::entries, "entries", &prototype, 0, interpreter);
+
+        let symbol_iterator = interpreter.well_known_symbols().iterator_symbol();
+        prototype.set_property(
+            symbol_iterator,
+            Property::default().value(prototype.get_field("values")),
+        );
 
         let array = make_constructor_fn(
             Self::NAME,

boa/src/builtins/array/tests.rs

@@ -1078,3 +1078,135 @@ fn call_array_constructor_with_one_argument() {
     // let result = forward(&mut engine, "one.length");
     // assert_eq!(result, "1");
 }
+
+#[test]
+fn array_values_simple() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [1, 2, 3].values();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "1");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "2");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "3");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_keys_simple() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [1, 2, 3].keys();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "0");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "1");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "2");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_entries_simple() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [1, 2, 3].entries();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "[ 0, 1 ]");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "[ 1, 2 ]");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "[ 2, 3 ]");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_values_empty() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [].values();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_values_sparse() {
+    let mut engine = Context::new();
+    let init = r#"
+        var array = Array();
+        array[3] = 5;
+        var iterator = array.values();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "5");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_symbol_iterator() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [1, 2, 3][Symbol.iterator]();
+        var next = iterator.next();
+    "#;
+    forward(&mut engine, init);
+    assert_eq!(forward(&mut engine, "next.value"), "1");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "2");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "3");
+    assert_eq!(forward(&mut engine, "next.done"), "false");
+    forward(&mut engine, "next = iterator.next()");
+    assert_eq!(forward(&mut engine, "next.value"), "undefined");
+    assert_eq!(forward(&mut engine, "next.done"), "true");
+}
+
+#[test]
+fn array_values_symbol_iterator() {
+    let mut engine = Context::new();
+    let init = r#"
+        var iterator = [1, 2, 3].values();
+        iterator === iterator[Symbol.iterator]();
+    "#;
+    assert_eq!(forward(&mut engine, init), "true");
+}