fix wasteful to_python() calls checking for undefined (#1580)

Author: davidhewitt

src/validators/model.rs

@@ -263,7 +263,7 @@ impl ModelValidator {
         let output = self.validator.validate(py, input, state)?;
 
         if self.root_model {
-            let fields_set = if input.to_object(py).is(&self.undefined) {
+            let fields_set = if input.as_python().is_some_and(|py_input| py_input.is(&self.undefined)) {
                 PySet::empty(py)?
             } else {
                 PySet::new(py, [&String::from(ROOT_FIELD)])?
@@ -304,7 +304,7 @@ impl ModelValidator {
         let instance = create_class(self.class.bind(py))?;
 
         if self.root_model {
-            let fields_set = if input.to_object(py).is(&self.undefined) {
+            let fields_set = if input.as_python().is_some_and(|py_input| py_input.is(&self.undefined)) {
                 PySet::empty(py)?
             } else {
                 PySet::new(py, [&String::from(ROOT_FIELD)])?

src/validators/with_default.rs

@@ -157,7 +157,7 @@ impl Validator for WithDefaultValidator {
         input: &(impl Input<'py> + ?Sized),
         state: &mut ValidationState<'_, 'py>,
     ) -> ValResult<PyObject> {
-        if input.to_object(py).is(&self.undefined) {
+        if input.as_python().is_some_and(|py_input| py_input.is(&self.undefined)) {
             Ok(self.default_value(py, None::<usize>, state)?.unwrap())
         } else {
             match self.validator.validate(py, input, state) {