avm2: Implement String.length

core/src/avm2/globals/string.rs

@@ -1,12 +1,12 @@
 //! `String` impl
 
-use crate::avm2::activation::Activation;
+use crate::avm2::class::{Class, ClassAttributes};
-use crate::avm2::class::Class;
 use crate::avm2::method::Method;
 use crate::avm2::names::{Namespace, QName};
 use crate::avm2::object::{Object, TObject};
 use crate::avm2::value::Value;
 use crate::avm2::Error;
+use crate::avm2::{activation::Activation, traits::Trait};
 use gc_arena::{GcCell, MutationContext};
 
 /// Implements `String`'s instance initializer.
@@ -39,13 +39,38 @@ pub fn class_init<'gc>(
     Ok(Value::Undefined)
 }
 
+/// Implements `length` property's getter
+fn length<'gc>(
+    activation: &mut Activation<'_, 'gc, '_>,
+    this: Option<Object<'gc>>,
+    _args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error> {
+    if let Some(this) = this {
+        if let Value::String(s) = this.value_of(activation.context.gc_context)? {
+            return Ok(s.encode_utf16().count().into());
+        }
+    }
+
+    Ok(Value::Undefined)
+}
+
 /// Construct `String`'s class.
 pub fn create_class<'gc>(mc: MutationContext<'gc, '_>) -> GcCell<'gc, Class<'gc>> {
-    Class::new(
+    let class = Class::new(
         QName::new(Namespace::public(), "String"),
         Some(QName::new(Namespace::public(), "Object").into()),
         Method::from_builtin(instance_init),
         Method::from_builtin(class_init),
         mc,
-    )
+    );
+
+    let mut write = class.write(mc);
+    write.set_attributes(ClassAttributes::FINAL | ClassAttributes::SEALED);
+
+    write.define_instance_trait(Trait::from_getter(
+        QName::new(Namespace::public(), "length"),
+        Method::from_builtin(length),
+    ));
+
+    class
 }

core/tests/regression_tests.rs

@@ -505,6 +505,7 @@ swf_tests! {
     (as3_movieclip_dispatchevent_target, "avm2/movieclip_dispatchevent_target", 1),
     (as3_movieclip_dispatchevent_selfadd, "avm2/movieclip_dispatchevent_selfadd", 1),
     (as3_string_constr, "avm2/string_constr", 1),
+    (as3_string_length, "avm2/string_length", 1),
 }
 
 // TODO: These tests have some inaccuracies currently, so we use approx_eq to test that numeric values are close enough.

core/tests/swfs/avm2/string_length/Test.as

@@ -0,0 +1,20 @@
+package {
+	public class Test {}
+}
+
+trace("//\"\".length;");
+trace("".length);
+trace("//\"\\n\\r\".length;");
+trace("\n\r".length);
+trace("//\"\\t\".length;");
+trace("\t".length);
+trace("//\"abc012aáâ\".length;");
+trace("abc012aáâ".length);
+trace("//\"你好こんにちは\".length;");
+trace("你好こんにちは".length);
+trace("//\"مَرحَبًا\".length;");
+trace("مَرحَبًا".length);
+trace("//\"😀\".length;");
+trace("😀".length);
+trace("//\"👨‍👨‍👧‍👦\".length;");
+trace("👨‍👨‍👧‍👦".length);

core/tests/swfs/avm2/string_length/output.txt

@@ -0,0 +1,16 @@
+//"".length;
+0
+//"\n\r".length;
+2
+//"\t".length;
+1
+//"abc012aáâ".length;
+9
+//"你好こんにちは".length;
+7
+//"مَرحَبًا".length;
+8
+//"😀".length;
+2
+//"👨‍👨‍👧‍👦".length;
+11