avm2: Implement fscommand()

core/src/avm2/globals/flash/system.as

@@ -1,7 +1,4 @@
 package flash.system {
-    import __ruffle__.stub_method;
-    public function fscommand(command:String, args:String = ""):void {
-        stub_method("flash.system", "fscommand");
-    }
+    public native function fscommand(command:String, args:String = ""):void;
 }
 

core/src/avm2/globals/flash/system.rs

@@ -5,3 +5,29 @@ pub mod application_domain;
 pub mod capabilities;
 pub mod security;
 pub mod system;
+
+use crate::avm2::activation::Activation;
+use crate::avm2::object::Object;
+use crate::avm2::parameters::ParametersExt;
+use crate::avm2::value::Value;
+use crate::avm2::Error;
+
+/// Implements `flash.system.fscommand` method
+pub fn fscommand<'gc>(
+    activation: &mut Activation<'_, 'gc>,
+    _this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error<'gc>> {
+    let command = args.get_string(activation, 0)?;
+    let args = args.get_string(activation, 1)?;
+
+    if !activation
+        .context
+        .external_interface
+        .invoke_fs_command(&command.to_utf8_lossy(), &args.to_utf8_lossy())
+    {
+        tracing::warn!("Unknown FSCommand: {}", command);
+    }
+
+    Ok(Value::Undefined)
+}