Put JSON functions on the object, not the prototype (#325)

* Move JSON functions to the object, not the prototype

* Fix Value.to_json and add JSON tests

* Update boa/src/builtins/json.rs

* Update boa/src/builtins/json.rs

* Update boa/src/builtins/json.rs

* Update json.rs

* Fix fmt issues.

Co-authored-by: Iban Eguia <razican@protonmail.ch>
Co-authored-by: HalidOdat <halidodat@gmail.com>

boa/src/builtins/json.rs

@@ -1,10 +1,22 @@
+//! This module implements the global `JSON` object.
+//!
+//! The `JSON` object contains methods for parsing [JavaScript Object Notation (JSON)][json]
+//! and converting values to JSON. It can't be called or constructed, and aside from its
+//! two method properties, it has no interesting functionality of its own.
+//!
+//! More information:
+//!  - [ECMAScript reference][spec]
+//!  - [MDN documentation][mdn]
+//!  - [JSON specification][json]
+//!
+//! [spec]: https://tc39.es/ecma262/#sec-json
+//! [json]: https://www.json.org/json-en.html
+//! [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON
+
 use crate::builtins::function::NativeFunctionData;
-use crate::builtins::object::{Object, ObjectKind, PROTOTYPE};
-/// The JSON Object
-/// <https://tc39.es/ecma262/#sec-json-object>
 use crate::builtins::value::{to_value, ResultValue, Value, ValueData};
 use crate::exec::Interpreter;
-use serde_json::{self, to_string_pretty, Value as JSONValue};
+use serde_json::{self, Value as JSONValue};
 
 /// Parse a JSON string into a Javascript object
 /// <https://tc39.es/ecma262/#sec-json.parse>
@@ -20,23 +32,42 @@ pub fn parse(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
         Err(err) => Err(to_value(err.to_string())),
     }
 }
+
 /// Process a Javascript object into a JSON string
 pub fn stringify(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
     let obj = args.get(0).expect("cannot get argument for JSON.stringify");
-    let json = obj.to_json();
-    Ok(to_value(to_string_pretty(&json).expect("")))
+    let json = obj.to_json().to_string();
+    Ok(to_value(json))
 }
 
 /// Create a new `JSON` object
 pub fn create_constructor(global: &Value) -> Value {
-    let mut json = Object::default();
-    json.kind = ObjectKind::Ordinary;
+    let json = ValueData::new_obj(Some(global));
+
+    make_builtin_fn!(parse, named "parse", with length 2, of json);
+    make_builtin_fn!(stringify, named "stringify", with length 3, of json);
 
-    let prototype = ValueData::new_obj(Some(global));
-    make_builtin_fn!(parse, named "parse", with length 2, of prototype);
-    make_builtin_fn!(stringify, named "stringify", with length 3, of prototype);
+    to_value(json)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{exec::Executor, forward, realm::Realm};
 
-    let json_value = to_value(json);
-    json_value.set_field_slice(PROTOTYPE, prototype);
-    json_value
+    #[test]
+    fn json_sanity() {
+        let realm = Realm::create();
+        let mut engine = Executor::new(realm);
+        assert_eq!(
+            forward(&mut engine, r#"JSON.parse('{"aaa":"bbb"}').aaa == 'bbb'"#),
+            "true"
+        );
+        assert_eq!(
+            forward(
+                &mut engine,
+                r#"JSON.stringify({aaa: 'bbb'}) == '{"aaa":"bbb"}'"#
+            ),
+            "true"
+        );
+    }
 }

boa/src/builtins/value/mod.rs

@@ -586,12 +586,12 @@ impl ValueData {
             | ValueData::Function(_) => JSONValue::Null,
             ValueData::Boolean(b) => JSONValue::Bool(b),
             ValueData::Object(ref obj) => {
-                let mut new_obj = Map::new();
-                for (k, v) in obj.borrow().internal_slots.iter() {
-                    if k != INSTANCE_PROTOTYPE {
-                        new_obj.insert(k.clone(), v.to_json());
-                    }
-                }
+                let new_obj = obj
+                    .borrow()
+                    .properties
+                    .iter()
+                    .map(|(k, _)| (k.clone(), self.get_field_slice(k).to_json()))
+                    .collect::<Map<String, JSONValue>>();
                 JSONValue::Object(new_obj)
             }
             ValueData::String(ref str) => JSONValue::String(str.clone()),