Add support for the reviver function to JSON.parse (#410)

boa/src/builtins/json/mod.rs

@@ -37,8 +37,7 @@ mod tests;
 ///
 /// [spec]: https://tc39.es/ecma262/#sec-json.parse
 /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse
-// TODO: implement optional revever argument.
-pub fn parse(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
+pub fn parse(_: &mut Value, args: &[Value], interpreter: &mut Interpreter) -> ResultValue {
     match serde_json::from_str::<JSONValue>(
         &args
             .get(0)
@@ -46,11 +45,53 @@ pub fn parse(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultValue
             .clone()
             .to_string(),
     ) {
-        Ok(json) => Ok(Value::from(json)),
+        Ok(json) => {
+            let j = Value::from(json);
+            match args.get(1) {
+                Some(reviver) if reviver.is_function() => {
+                    let mut holder = Value::new_object(None);
+                    holder.set_field(Value::from(""), j);
+                    walk(reviver, interpreter, &mut holder, Value::from(""))
+                }
+                _ => Ok(j),
+            }
+        }
         Err(err) => Err(Value::from(err.to_string())),
     }
 }
 
+/// This is a translation of the [Polyfill implementation][polyfill]
+///
+/// This function recursively walks the structure, passing each key-value pair to the reviver function
+/// for possible transformation.
+///
+/// [polyfill]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse
+fn walk(
+    reviver: &Value,
+    interpreter: &mut Interpreter,
+    holder: &mut Value,
+    key: Value,
+) -> ResultValue {
+    let mut value = holder.get_field(key.clone());
+
+    let obj = value.as_object().as_deref().cloned();
+    if let Some(obj) = obj {
+        for key in obj.properties.keys() {
+            let v = walk(reviver, interpreter, &mut value, Value::from(key.as_str()));
+            match v {
+                Ok(v) if !v.is_undefined() => {
+                    value.set_field(Value::from(key.as_str()), v);
+                }
+                Ok(_) => {
+                    value.remove_property(key.as_str());
+                }
+                Err(_v) => {}
+            }
+        }
+    }
+    interpreter.call(reviver, holder, &[key, value])
+}
+
 /// `JSON.stringify( value[, replacer[, space]] )`
 ///
 /// This `JSON` method converts a JavaScript object or value to a JSON string.

boa/src/builtins/json/tests.rs

@@ -1,4 +1,4 @@
-use crate::{exec::Interpreter, forward, realm::Realm};
+use crate::{exec::Interpreter, forward, forward_val, realm::Realm};
 
 #[test]
 fn json_sanity() {
@@ -189,3 +189,50 @@ fn json_stringify_return_undefined() {
     assert_eq!(actual_function, expected);
     assert_eq!(actual_symbol, expected);
 }
+
+#[test]
+fn json_parse_array_with_reviver() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+    let result = forward_val(
+        &mut engine,
+        r#"JSON.parse('[1,2,3,4]', function(k, v){
+            if (typeof v == 'number') {
+                return v * 2;
+            } else {
+                v
+        }})"#,
+    )
+    .unwrap();
+    assert_eq!(result.get_field("0").to_number() as u8, 2u8);
+    assert_eq!(result.get_field("1").to_number() as u8, 4u8);
+    assert_eq!(result.get_field("2").to_number() as u8, 6u8);
+    assert_eq!(result.get_field("3").to_number() as u8, 8u8);
+}
+
+#[test]
+fn json_parse_object_with_reviver() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+    let result = forward(
+        &mut engine,
+        r#"
+        var myObj = new Object();
+        myObj.firstname = "boa";
+        myObj.lastname = "snake";
+        var jsonString = JSON.stringify(myObj);
+
+        function dataReviver(key, value) {
+            if (key == 'lastname') {
+                return 'interpreter';
+            } else {
+                return value;
+            }
+        }
+
+        var jsonObj = JSON.parse(jsonString, dataReviver);
+
+        JSON.stringify(jsonObj);"#,
+    );
+    assert_eq!(result, r#"{"firstname":"boa","lastname":"interpreter"}"#);
+}

boa/src/builtins/value/mod.rs

@@ -690,7 +690,10 @@ impl ValueData {
                 for (idx, json) in vs.iter().enumerate() {
                     new_obj.properties.insert(
                         idx.to_string(),
-                        Property::default().value(Value::from(json.clone())),
+                        Property::default()
+                            .value(Value::from(json.clone()))
+                            .writable(true)
+                            .configurable(true),
                     );
                 }
                 new_obj.properties.insert(
@@ -704,7 +707,10 @@ impl ValueData {
                 for (key, json) in obj.iter() {
                     new_obj.properties.insert(
                         key.clone(),
-                        Property::default().value(Value::from(json.clone())),
+                        Property::default()
+                            .value(Value::from(json.clone()))
+                            .writable(true)
+                            .configurable(true),
                     );
                 }