From 89b487d36e6df8964b21decf7897f580741f7a3d Mon Sep 17 00:00:00 2001
From: Nick Little <n14little@gmail.com>
Date: Mon, 18 May 2020 20:54:04 -0500
Subject: [PATCH] handle json stringification for arrays

---
 boa/src/builtins/json/tests.rs | 40 ++++++++++++++++++++++++++++++++++
 boa/src/builtins/value/mod.rs  | 38 +++++++++++++++++++++++---------
 2 files changed, 68 insertions(+), 10 deletions(-)

diff --git a/boa/src/builtins/json/tests.rs b/boa/src/builtins/json/tests.rs
index 14cb344e5ff..34c6b9266a9 100644
--- a/boa/src/builtins/json/tests.rs
+++ b/boa/src/builtins/json/tests.rs
@@ -102,3 +102,43 @@ fn json_stringify_replacer_function() {
     let expected = forward(&mut engine, r#"'{"bbb":2}'"#);
     assert_eq!(actual, expected);
 }
+
+#[test]
+fn json_stringify_arrays() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let actual = forward(&mut engine, r#"JSON.stringify(['a', 'b'])"#);
+    let expected = forward(&mut engine, r#"'["a","b"]'"#);
+
+    assert_eq!(actual, expected);
+}
+
+#[test]
+fn json_stringify_object_array() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let actual = forward(&mut engine, r#"JSON.stringify([{a: 'b'}, {b: 'c'}])"#);
+    let expected = forward(&mut engine, r#"'[{"a":"b"},{"b":"c"}]'"#);
+
+    assert_eq!(actual, expected);
+}
+
+#[test]
+fn json_stringify_array_converts_undefined_to_null() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let actual = forward(&mut engine, r#"JSON.stringify([undefined])"#);
+    let expected = forward(&mut engine, r#"'[null]'"#);
+
+    assert_eq!(actual, expected);
+}
+
+#[test]
+fn json_stringify_array_converts_function_to_null() {
+    let realm = Realm::create();
+    let mut engine = Executor::new(realm);
+    let actual = forward(&mut engine, r#"JSON.stringify([() => {}])"#);
+    let expected = forward(&mut engine, r#"'[null]'"#);
+
+    assert_eq!(actual, expected);
+}
diff --git a/boa/src/builtins/value/mod.rs b/boa/src/builtins/value/mod.rs
index f4c813f7143..b461a7f8aaf 100644
--- a/boa/src/builtins/value/mod.rs
+++ b/boa/src/builtins/value/mod.rs
@@ -682,24 +682,42 @@ impl ValueData {
     /// Conversts the `Value` to `JSON`.
     pub fn to_json(&self) -> JSONValue {
         match *self {
-            Self::Null | Self::Symbol(_) | Self::Undefined => JSONValue::Null,
+            Self::Null => JSONValue::Null,
             Self::Boolean(b) => JSONValue::Bool(b),
             Self::Object(ref obj) => {
-                let mut new_obj = Map::new();
-                obj.borrow().properties.iter().for_each(|(k, _)| {
-                    let key = k.clone();
-                    let value = self.get_field_slice(k);
-                    if !value.is_undefined() && !value.is_function() {
-                        new_obj.insert(key, value.to_json());
-                    }
-                });
-                JSONValue::Object(new_obj)
+                if obj.borrow().kind == ObjectKind::Array {
+                    let mut arr: Vec<JSONValue> = Vec::new();
+                    obj.borrow().properties.iter().for_each(|(k, _)| {
+                        if k != "length" {
+                            let value = self.get_field_slice(k);
+                            if value.is_undefined() || value.is_function() {
+                                arr.push(JSONValue::Null);
+                            } else {
+                                arr.push(self.get_field_slice(k).to_json());
+                            }
+                        }
+                    });
+                    JSONValue::Array(arr)
+                } else {
+                    let mut new_obj = Map::new();
+                    obj.borrow().properties.iter().for_each(|(k, _)| {
+                        let key = k.clone();
+                        let value = self.get_field_slice(k);
+                        if !value.is_undefined() && !value.is_function() {
+                            new_obj.insert(key, value.to_json());
+                        }
+                    });
+                    JSONValue::Object(new_obj)
+                }
             }
             Self::String(ref str) => JSONValue::String(str.clone()),
             Self::Rational(num) => JSONValue::Number(
                 JSONNumber::from_f64(num).expect("Could not convert to JSONNumber"),
             ),
             Self::Integer(val) => JSONValue::Number(JSONNumber::from(val)),
+            Self::Symbol(_) | Self::Undefined => {
+                panic!("Symbols and Undefined depend on parent type");
+            }
         }
     }