From dd229aa5ffe8328631f4450ca7ff1da6b3c50a3a Mon Sep 17 00:00:00 2001
From: Nick Little <n14little@gmail.com>
Date: Thu, 14 May 2020 23:16:39 -0500
Subject: [PATCH] WIP: to_json returns undefined to null

---
 boa/src/builtins/json/mod.rs   | 27 ++++++++++++++++++++-------
 boa/src/builtins/json/tests.rs | 18 ++++++++++++++++++
 2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/boa/src/builtins/json/mod.rs b/boa/src/builtins/json/mod.rs
index 122cd8b3a8a..2786475e4b0 100644
--- a/boa/src/builtins/json/mod.rs
+++ b/boa/src/builtins/json/mod.rs
@@ -15,6 +15,7 @@
 
 use crate::builtins::{
     object::ObjectKind,
+    property::Property,
     value::{ResultValue, Value, ValueData},
 };
 use crate::exec::Interpreter;
@@ -66,7 +67,7 @@ pub fn parse(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultValue
 ///
 /// [spec]: https://tc39.es/ecma262/#sec-json.stringify
 /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
-pub fn stringify(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
+pub fn stringify(_: &mut Value, args: &[Value], interpreter: &mut Interpreter) -> ResultValue {
     let object = args.get(0).expect("cannot get argument for JSON.stringify");
     if args.len() == 1 {
         let json = object.to_json().to_string();
@@ -77,9 +78,9 @@ pub fn stringify(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultVa
     if let Some(arg) = args.get(1) {
         if let ValueData::Object(ref obj) = arg.data() {
             let derefed_obj = (*obj).deref();
-            let borrowed_derefed_obj = derefed_obj.borrow();
-            if borrowed_derefed_obj.kind == ObjectKind::Array {
-                for (key, value) in borrowed_derefed_obj.properties.iter() {
+            let borrowed_derefed_replacer = derefed_obj.borrow();
+            if borrowed_derefed_replacer.kind == ObjectKind::Array {
+                for (key, value) in borrowed_derefed_replacer.properties.iter() {
                     if let Some(Value(x)) = &value.value {
                         if key != "length" {
                             object_to_return.set_property(
@@ -89,10 +90,22 @@ pub fn stringify(_: &mut Value, args: &[Value], _: &mut Interpreter) -> ResultVa
                         }
                     }
                 }
-                return Ok(Value::from(object_to_return.to_json().to_string()));
-            } else {
-                unimplemented!("replacer only supports arrays at this time");
+            } else if borrowed_derefed_replacer.kind == ObjectKind::Function {
+                if let ValueData::Object(ref obj) = object.data() {
+                    let derefed_obj = (*obj).deref();
+                    let borrowed_deref_obj = derefed_obj.borrow();
+                    for (key, val) in borrowed_deref_obj.properties.iter() {
+                        if let Some(value) = &val.value {
+                            let mut this_arg = object.clone();
+                            object_to_return.set_property(
+                                String::from(key),
+                                Property::default().value(interpreter.call(arg, &mut this_arg, &[Value::string(key), Value::from(value)]).unwrap()),
+                            );
+                        }
+                    }
+                }
             }
+            return Ok(Value::from(object_to_return.to_json().to_string()));
         }
     }
     panic!("cannot get replacer for JSON.stringify");
diff --git a/boa/src/builtins/json/tests.rs b/boa/src/builtins/json/tests.rs
index f852f84f3b6..cec9ceb090c 100644
--- a/boa/src/builtins/json/tests.rs
+++ b/boa/src/builtins/json/tests.rs
@@ -40,3 +40,21 @@ fn json_stringify_replacer_array_numbers() {
     let expected = forward(&mut engine, r#"'{"1":"bbb","2":"ccc"}'"#);
     assert_eq!(actual, expected);
 }
+
+#[test]
+fn json_stringify_replacer_function() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let actual = forward(
+        &mut engine,
+        r#"JSON.stringify({ aaa: 1, bbb: 2}, (key, value) => {
+            if (key === 'aaa') {
+                return undefined;
+            }
+
+            return value;
+        })"#,
+    );
+    let expected = forward(&mut engine, r#"'{"bbb":2}'"#);
+    assert_eq!(actual, expected);
+}