fix NamedArray.imag and NamedArray.real typing info (pydata#8369)

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

Author: andersy005

xarray/core/variable.py

@@ -2365,6 +2365,28 @@ def notnull(self, keep_attrs: bool | None = None):
             keep_attrs=keep_attrs,
         )
 
+    @property
+    def imag(self) -> Variable:
+        """
+        The imaginary part of the variable.
+
+        See Also
+        --------
+        numpy.ndarray.imag
+        """
+        return self._new(data=self.data.imag)
+
+    @property
+    def real(self) -> Variable:
+        """
+        The real part of the variable.
+
+        See Also
+        --------
+        numpy.ndarray.real
+        """
+        return self._new(data=self.data.real)
+
     def __array_wrap__(self, obj, context=None):
         return Variable(self.dims, obj)
 

xarray/namedarray/_typing.py

@@ -138,6 +138,14 @@ def __array_function__(
     ) -> Any:
         ...
 
+    @property
+    def imag(self) -> _arrayfunction[_ShapeType_co, Any]:
+        ...
+
+    @property
+    def real(self) -> _arrayfunction[_ShapeType_co, Any]:
+        ...
+
 
 # Corresponds to np.typing.NDArray:
 _ArrayFunction = _arrayfunction[Any, np.dtype[_ScalarType_co]]

xarray/namedarray/core.py

@@ -22,11 +22,15 @@
 from xarray.core import dtypes, formatting, formatting_html
 from xarray.namedarray._aggregations import NamedArrayAggregations
 from xarray.namedarray._typing import (
+    _arrayapi,
     _arrayfunction_or_api,
     _chunkedarray,
+    _dtype,
     _DType_co,
     _ScalarType_co,
     _ShapeType_co,
+    _SupportsImag,
+    _SupportsReal,
 )
 from xarray.namedarray.utils import _default, is_duck_dask_array, to_0d_object_array
 
@@ -513,26 +517,39 @@ def data(self, data: duckarray[Any, _DType_co]) -> None:
         self._data = data
 
     @property
-    def imag(self) -> Self:
+    def imag(
+        self: NamedArray[_ShapeType, np.dtype[_SupportsImag[_ScalarType]]],  # type: ignore[type-var]
+    ) -> NamedArray[_ShapeType, _dtype[_ScalarType]]:
         """
         The imaginary part of the array.
 
         See Also
         --------
         numpy.ndarray.imag
         """
-        return self._replace(data=self.data.imag)  # type: ignore
+        if isinstance(self._data, _arrayapi):
+            from xarray.namedarray._array_api import imag
+
+            return imag(self)
+
+        return self._new(data=self._data.imag)
 
     @property
-    def real(self) -> Self:
+    def real(
+        self: NamedArray[_ShapeType, np.dtype[_SupportsReal[_ScalarType]]],  # type: ignore[type-var]
+    ) -> NamedArray[_ShapeType, _dtype[_ScalarType]]:
         """
         The real part of the array.
 
         See Also
         --------
         numpy.ndarray.real
         """
-        return self._replace(data=self.data.real)  # type: ignore
+        if isinstance(self._data, _arrayapi):
+            from xarray.namedarray._array_api import real
+
+            return real(self)
+        return self._new(data=self._data.real)
 
     def __dask_tokenize__(self) -> Hashable:
         # Use v.data, instead of v._data, in order to cope with the wrappers

xarray/tests/test_namedarray.py

@@ -168,13 +168,25 @@ def test_data(random_inputs: np.ndarray[Any, Any]) -> None:
 
 
 def test_real_and_imag() -> None:
-    named_array: NamedArray[Any, Any]
-    named_array = NamedArray(["x"], np.arange(3) - 1j * np.arange(3))
-    expected_real = np.arange(3)
-    assert np.array_equal(named_array.real.data, expected_real)
+    expected_real: np.ndarray[Any, np.dtype[np.float64]]
+    expected_real = np.arange(3, dtype=np.float64)
+
+    expected_imag: np.ndarray[Any, np.dtype[np.float64]]
+    expected_imag = -np.arange(3, dtype=np.float64)
+
+    arr: np.ndarray[Any, np.dtype[np.complex128]]
+    arr = expected_real + 1j * expected_imag
+
+    named_array: NamedArray[Any, np.dtype[np.complex128]]
+    named_array = NamedArray(["x"], arr)
+
+    actual_real: duckarray[Any, np.dtype[np.float64]] = named_array.real.data
+    assert np.array_equal(actual_real, expected_real)
+    assert actual_real.dtype == expected_real.dtype
 
-    expected_imag = -np.arange(3)
-    assert np.array_equal(named_array.imag.data, expected_imag)
+    actual_imag: duckarray[Any, np.dtype[np.float64]] = named_array.imag.data
+    assert np.array_equal(actual_imag, expected_imag)
+    assert actual_imag.dtype == expected_imag.dtype
 
 
 # Additional tests as per your original class-based code
@@ -347,7 +359,9 @@ def _new(
 
 def test_replace_namedarray() -> None:
     dtype_float = np.dtype(np.float32)
+    np_val: np.ndarray[Any, np.dtype[np.float32]]
     np_val = np.array([1.5, 3.2], dtype=dtype_float)
+    np_val2: np.ndarray[Any, np.dtype[np.float32]]
     np_val2 = 2 * np_val
 
     narr_float: NamedArray[Any, np.dtype[np.float32]]