Enable obj[key] = value syntax. (#161)

* wip: setting keys in objects

* handle array case when setting objects

src/lib/exec.rs

@@ -415,6 +415,13 @@ impl Executor for Interpreter {
                         let val_obj = self.run(obj)?;
                         val_obj.borrow().set_field(field.clone(), val.clone());
                     }
+                    ExprDef::GetField(ref obj, ref field) => {
+                        let val_obj = self.run(obj)?;
+                        let val_field = self.run(field)?;
+                        val_obj
+                            .borrow()
+                            .set_field(val_field.to_string(), val.clone());
+                    }
                     _ => (),
                 }
                 Ok(val)
@@ -703,4 +710,45 @@ mod tests {
 
         assert_eq!(exec(scenario), pass);
     }
+
+    #[test]
+    fn object_field_set() {
+        let scenario = r#"
+        let m = {};
+        m['key'] = 22;
+        m['key']
+        "#;
+        assert_eq!(exec(scenario), String::from("22"));
+    }
+
+    #[test]
+    fn array_field_set() {
+        let element_changes = r#"
+        let m = [1, 2, 3];
+        m[1] = 5;
+        m[1]
+        "#;
+        assert_eq!(exec(element_changes), String::from("5"));
+
+        let length_changes = r#"
+        let m = [1, 2, 3];
+        m[10] = 52;
+        m.length
+        "#;
+        assert_eq!(exec(length_changes), String::from("11"));
+
+        let negative_index_wont_affect_length = r#"
+        let m = [1, 2, 3];
+        m[-11] = 5;
+        m.length
+        "#;
+        assert_eq!(exec(negative_index_wont_affect_length), String::from("3"));
+
+        let non_num_key_wont_affect_length = r#"
+        let m = [1, 2, 3];
+        m["magic"] = 5;
+        m.length
+        "#;
+        assert_eq!(exec(non_num_key_wont_affect_length), String::from("3"));
+    }
 }

src/lib/js/object.rs

@@ -402,7 +402,7 @@ impl Object {
     }
 }
 
-#[derive(Trace, Finalize, Clone, Debug)]
+#[derive(Trace, Finalize, Clone, Debug, Eq, PartialEq)]
 pub enum ObjectKind {
     Function,
     Array,

src/lib/js/value.rs

@@ -402,6 +402,17 @@ impl ValueData {
     pub fn set_field(&self, field: String, val: Value) -> Value {
         match *self {
             ValueData::Object(ref obj) => {
+                if obj.borrow().kind == ObjectKind::Array {
+                    if let Ok(num) = field.parse::<usize>() {
+                        if num > 0 {
+                            let len: i32 = from_value(self.get_field_slice("length"))
+                                .expect("Could not convert argument to i32");
+                            if len < (num + 1) as i32 {
+                                self.set_field_slice("length", to_value(num + 1));
+                            }
+                        }
+                    }
+                }
                 obj.borrow_mut()
                     .properties
                     .insert(field, Property::default().value(val.clone()));