delegate more to other existing functions

xarray/core/computation.py

@@ -1346,9 +1346,9 @@ def _calc_idxminmax(
     array,
     func: Callable,
     dim: Optional[Hashable],
-    skipna: Optional[bool],
+    skipna: bool = None,
     fill_value: Any = None,
-    keep_attrs: Optional[bool],
+    keep_attrs: bool = None,
     **kwargs: Any,
 ):
     """Apply common operations for idxmin and idxmax."""
@@ -1379,7 +1379,9 @@ def _calc_idxminmax(
         array = array.where(~allna, 0)
 
     # This will run argmin or argmax.
-    indx = func(array, dim=dim, axis=None, keep_attrs=False, skipna=skipna, **kwargs)
+    indx = func(
+        array, dim=dim, axis=None, keep_attrs=keep_attrs, skipna=skipna, **kwargs
+    )
 
     # Get the coordinate we want.
     coordarray = array[dim]
@@ -1399,8 +1401,7 @@ def _calc_idxminmax(
     # The dim is gone but we need to remove the corresponding coordinate.
     del res.coords[dim]
 
-    # Put the attrs back in if needed
-    if keep_attrs:
-        res.attrs = array.attrs
+    # Copy attributes from argmin/argmax, if any
+    res.attrs = indx.attrs
 
     return res

xarray/core/dataarray.py

@@ -3512,8 +3512,8 @@ def idxmin(
         self,
         dim: Hashable = None,
         skipna: bool = None,
-        fill_value: Any = np.NaN,
-        keep_attrs: Optional[bool] = False,
+        fill_value: Any = dtypes.NA,
+        keep_attrs: bool = None,
         **kwargs: Any,
     ) -> "DataArray":
         """Return the coordinate of the minimum value along a dimension.
@@ -3610,8 +3610,8 @@ def idxmax(
         self,
         dim: Hashable = None,
         skipna: bool = None,
-        fill_value: Any = np.NaN,
-        keep_attrs: Optional[bool] = False,
+        fill_value: Any = dtypes.NA,
+        keep_attrs: bool = None,
         **kwargs: Any,
     ) -> "DataArray":
         """Return the coordinate of the maximum value along a dimension.

xarray/core/dataset.py

@@ -6098,8 +6098,8 @@ def idxmin(
         self,
         dim: Hashable = None,
         skipna: bool = None,
-        fill_value: Any = np.NaN,
-        keep_attrs: bool = False,
+        fill_value: Any = dtypes.NA,
+        keep_attrs: bool = None,
         **kwargs: Any,
     ) -> "Dataset":
         """Return the coordinate of the minimum value along a dimension.
@@ -6197,8 +6197,8 @@ def idxmax(
         self,
         dim: Hashable = None,
         skipna: bool = None,
-        fill_value: Any = np.NaN,
-        keep_attrs: Optional[bool] = False,
+        fill_value: Any = dtypes.NA,
+        keep_attrs: bool = None,
         **kwargs: Any,
     ) -> "Dataset":
         """Return the coordinate of the maximum value along a dimension.