fix binding cpp

bindings/cpp/src/async.rs

@@ -103,6 +103,7 @@ unsafe fn operator_write(op: ffi::OperatorPtr, path: String, bs: Vec<u8>) -> Rus
             .0
             .write(&path, bs)
             .await
+            .map(|_| ())
             .map_err(|e| CxxAsyncException::new(e.to_string().into_boxed_str()))?)
     })
 }

core/tests/behavior/async_write.rs

@@ -670,6 +670,7 @@ pub async fn test_write_with_append_returns_metadata(op: Operator) -> Result<()>
     let (content_two, _) = gen_bytes(op.info().full_capability());
 
     op.write_with(&path, content_one.clone())
+        .append(true)
         .await
         .expect("append file first time must success");