Implement spread for objects (#1364)

* Implement spread for objects

* Use copy_data_properties for object spread

* Use check_output for object spread test

boa/src/exec/tests.rs

@@ -118,6 +118,21 @@ fn object_field_set() {
     assert_eq!(&exec(scenario), "22");
 }
 
+#[test]
+fn object_spread() {
+    let scenario = r#"
+            var b = {x: -1, z: -3}
+            var a = {x: 1, y: 2, ...b};
+        "#;
+
+    check_output(&[
+        TestAction::Execute(scenario),
+        TestAction::TestEq("a.x", "-1"),
+        TestAction::TestEq("a.y", "2"),
+        TestAction::TestEq("a.z", "-3"),
+    ]);
+}
+
 #[test]
 fn spread_with_arguments() {
     let scenario = r#"

boa/src/syntax/ast/node/object/mod.rs

@@ -161,6 +161,20 @@ impl Executable for Object {
                         )
                     }
                 },
+                // [spec]: https://tc39.es/ecma262/#sec-runtime-semantics-propertydefinitionevaluation
+                PropertyDefinition::SpreadObject(node) => {
+                    let val = node.run(context)?;
+
+                    if val.is_null_or_undefined() {
+                        continue;
+                    }
+
+                    obj.as_object().unwrap().copy_data_properties::<String>(
+                        &val,
+                        vec![],
+                        context,
+                    )?;
+                }
                 _ => {} // unimplemented!("{:?} type of property", i),
             }
         }

boa/src/syntax/ast/node/object/tests.rs

@@ -1,3 +1,78 @@
+use crate::exec;
+
+#[test]
+fn spread_shallow_clone() {
+    let scenario = r#"
+        var a = { x: {} };
+        var aClone = { ...a };
+
+        a.x === aClone.x
+    "#;
+    assert_eq!(&exec(scenario), "true");
+}
+
+#[test]
+fn spread_merge() {
+    let scenario = r#"
+        var a = { x: 1, y: 2 };
+        var b = { x: -1, z: -3, ...a };
+
+        (b.x === 1) && (b.y === 2) && (b.z === -3)
+    "#;
+    assert_eq!(&exec(scenario), "true");
+}
+
+#[test]
+fn spread_overriding_properties() {
+    let scenario = r#"
+        var a = { x: 0, y: 0 };
+        var aWithOverrides = { ...a, ...{ x: 1, y: 2 } };
+
+        (aWithOverrides.x === 1) && (aWithOverrides.y === 2)
+    "#;
+    assert_eq!(&exec(scenario), "true");
+}
+
+#[test]
+fn spread_getters_in_initializer() {
+    let scenario = r#"
+        var a = { x: 42 };
+        var aWithXGetter = { ...a, get x() { throw new Error('not thrown yet') } };
+    "#;
+    assert_eq!(&exec(scenario), "undefined");
+}
+
+#[test]
+fn spread_getters_in_object() {
+    let scenario = r#"
+        var a = { x: 42 };
+        var aWithXGetter = { ...a, ... { get x() { throw new Error('not thrown yet') } } };
+    "#;
+    assert_eq!(&exec(scenario), "\"Error\": \"not thrown yet\"");
+}
+
+#[test]
+fn spread_setters() {
+    let scenario = r#"
+        var z = { set x(nexX) { throw new Error() }, ... { x: 1 } };
+    "#;
+    assert_eq!(&exec(scenario), "undefined");
+}
+
+#[test]
+fn spread_null_and_undefined_ignored() {
+    let scenario = r#"
+        var a = { ...null, ...undefined };
+        var count = 0;
+
+        for (key in a) { count++; }
+
+        count === 0
+    "#;
+
+    assert_eq!(&exec(scenario), "true");
+}
+
 #[test]
 fn fmt() {
     super::super::test_formatting(

boa/src/syntax/parser/expression/primary/object_initializer/tests.rs

@@ -273,3 +273,24 @@ fn check_object_shorthand_multiple_properties() {
         ],
     );
 }
+
+#[test]
+fn check_object_spread() {
+    let object_properties = vec![
+        PropertyDefinition::property("a", Const::from(1)),
+        PropertyDefinition::spread_object(Identifier::from("b")),
+    ];
+
+    check_parser(
+        "const x = { a: 1, ...b };
+        ",
+        vec![DeclarationList::Const(
+            vec![Declaration::new_with_identifier(
+                "x",
+                Some(Object::from(object_properties).into()),
+            )]
+            .into(),
+        )
+        .into()],
+    );
+}

boa/src/syntax/parser/tests.rs

@@ -4,7 +4,8 @@ use super::Parser;
 use crate::syntax::ast::{
     node::{
         field::GetConstField, ArrowFunctionDecl, Assign, BinOp, Call, Declaration, DeclarationList,
-        FormalParameter, FunctionDecl, Identifier, If, New, Node, Return, StatementList, UnaryOp,
+        FormalParameter, FunctionDecl, Identifier, If, New, Node, Object, PropertyDefinition,
+        Return, StatementList, UnaryOp,
     },
     op::{self, CompOp, LogOp, NumOp},
     Const,
@@ -299,6 +300,33 @@ fn increment_in_comma_op() {
     );
 }
 
+#[test]
+fn spread_in_object() {
+    let s = r#"
+    let x = {
+      a: 1,
+      ...b,
+    }
+    "#;
+
+    let object_properties = vec![
+        PropertyDefinition::property("a", Const::from(1)),
+        PropertyDefinition::spread_object(Identifier::from("b")),
+    ];
+
+    check_parser(
+        s,
+        vec![DeclarationList::Let(
+            vec![Declaration::new_with_identifier::<&str, Option<Node>>(
+                "x",
+                Some(Object::from(object_properties).into()),
+            )]
+            .into(),
+        )
+        .into()],
+    );
+}
+
 #[test]
 fn spread_in_arrow_function() {
     let s = r#"