Support GetOwnProperty for string exotic object (#1291)

* Support GetOwnProperty for string exotic object

* Fix clippy error

* change var name

* dont load from_u32 to namespace

* be explicit about attributes

* Update boa/src/object/internal_methods.rs

Co-authored-by: Iban Eguia <razican@protonmail.ch>

* fix utf16 emoji panic

* use map and ? operator

Co-authored-by: Iban Eguia <razican@protonmail.ch>

boa/src/builtins/string/tests.rs

@@ -1093,3 +1093,14 @@ fn unicode_iter() {
     assert_eq!(forward(&mut context, "next.value"), "undefined");
     assert_eq!(forward(&mut context, "next.done"), "true");
 }
+
+#[test]
+fn string_get_property() {
+    let mut context = Context::new();
+    assert_eq!(forward(&mut context, "'abc'[-1]"), "undefined");
+    assert_eq!(forward(&mut context, "'abc'[1]"), "\"b\"");
+    assert_eq!(forward(&mut context, "'abc'[2]"), "\"c\"");
+    assert_eq!(forward(&mut context, "'abc'[3]"), "undefined");
+    assert_eq!(forward(&mut context, "'abc'['foo']"), "undefined");
+    assert_eq!(forward(&mut context, "'😀'[0]"), "\"\\ud83d\"");
+}

boa/src/object/internal_methods.rs

@@ -390,6 +390,71 @@ impl GcObject {
         }
     }
 
+    /// Gets own property of 'Object'
+    ///
+    #[inline]
+    pub fn get_own_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
+        let _timer = BoaProfiler::global().start_event("Object::get_own_property", "object");
+
+        let object = self.borrow();
+        match object.data {
+            ObjectData::String(_) => self.string_exotic_get_own_property(key),
+            _ => self.ordinary_get_own_property(key),
+        }
+    }
+
+    /// StringGetOwnProperty abstract operation
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-stringgetownproperty
+    #[inline]
+    pub fn string_get_own_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
+        let object = self.borrow();
+
+        match key {
+            PropertyKey::Index(index) => {
+                let string = object.as_string().unwrap();
+                let pos = *index as usize;
+
+                if pos >= string.len() {
+                    return None;
+                }
+
+                let result_str = string.encode_utf16().nth(pos).map(|utf16_val| {
+                    char::from_u32(u32::from(utf16_val))
+                        .map_or_else(|| Value::from(format!("\\u{:x}", utf16_val)), Value::from)
+                })?;
+
+                let desc = PropertyDescriptor::from(DataDescriptor::new(
+                    result_str,
+                    Attribute::READONLY | Attribute::ENUMERABLE | Attribute::PERMANENT,
+                ));
+
+                Some(desc)
+            }
+            _ => None,
+        }
+    }
+
+    /// Gets own property of 'String' exotic object
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-string-exotic-objects-getownproperty-p
+    #[inline]
+    pub fn string_exotic_get_own_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
+        let desc = self.ordinary_get_own_property(key);
+
+        if desc.is_some() {
+            desc
+        } else {
+            self.string_get_own_property(key)
+        }
+    }
+
     /// The specification returns a Property Descriptor or Undefined.
     ///
     /// These are 2 separate types and we can't do that here.
@@ -399,9 +464,7 @@ impl GcObject {
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-getownproperty-p
     #[inline]
-    pub fn get_own_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
-        let _timer = BoaProfiler::global().start_event("Object::get_own_property", "object");
-
+    pub fn ordinary_get_own_property(&self, key: &PropertyKey) -> Option<PropertyDescriptor> {
         let object = self.borrow();
         let property = match key {
             PropertyKey::Index(index) => object.indexed_properties.get(&index),