Added `From<Bound<'py, T>>` impl for `PyClassInitializer<T>`. (#4214)

* Added `From<Bound<'py, T>>` impl for PyClassInitializer<T>.

* Added newsfragment entry.

* Added tests for pyclass constructors returning `Py<Self>` and `Bound<Self>`.

* Fixed tests.

* Updated tests to properly cover the new impl.

---------

Co-authored-by: jrudolph <jrudolph@anl.gov>

newsfragments/4214.added.md

@@ -0,0 +1 @@
+Added `From<Bound<'py, T>>` impl for `PyClassInitializer<T>`.

src/pyclass_init.rs

@@ -301,6 +301,13 @@ impl<T: PyClass> From<Py<T>> for PyClassInitializer<T> {
     }
 }
 
+impl<'py, T: PyClass> From<Bound<'py, T>> for PyClassInitializer<T> {
+    #[inline]
+    fn from(value: Bound<'py, T>) -> PyClassInitializer<T> {
+        PyClassInitializer::from(value.unbind())
+    }
+}
+
 // Implementation used by proc macros to allow anything convertible to PyClassInitializer<T> to be
 // the return value of pyclass #[new] method (optionally wrapped in `Result<U, E>`).
 impl<T, U> IntoPyCallbackOutput<PyClassInitializer<T>> for U

tests/test_class_new.rs

@@ -258,3 +258,43 @@ fn test_new_existing() {
         assert!(!obj5.is(&obj6));
     });
 }
+
+#[pyclass]
+struct NewReturnsPy;
+
+#[pymethods]
+impl NewReturnsPy {
+    #[new]
+    fn new(py: Python<'_>) -> PyResult<Py<NewReturnsPy>> {
+        Py::new(py, NewReturnsPy)
+    }
+}
+
+#[test]
+fn test_new_returns_py() {
+    Python::with_gil(|py| {
+        let type_ = py.get_type_bound::<NewReturnsPy>();
+        let obj = type_.call0().unwrap();
+        assert!(obj.is_exact_instance_of::<NewReturnsPy>());
+    })
+}
+
+#[pyclass]
+struct NewReturnsBound;
+
+#[pymethods]
+impl NewReturnsBound {
+    #[new]
+    fn new(py: Python<'_>) -> PyResult<Bound<'_, NewReturnsBound>> {
+        Bound::new(py, NewReturnsBound)
+    }
+}
+
+#[test]
+fn test_new_returns_bound() {
+    Python::with_gil(|py| {
+        let type_ = py.get_type_bound::<NewReturnsBound>();
+        let obj = type_.call0().unwrap();
+        assert!(obj.is_exact_instance_of::<NewReturnsBound>());
+    })
+}