more tests; fix issue with accessor masking

Author: dougbrn

src/nested_pandas/series/accessor.py

@@ -508,9 +508,9 @@ def __getitem__(self, key: str | list[str]) -> NestedSeries:
         # on the number of fields requested and their dtypes
         if isinstance(key, list):
             new_array = self._series.array.view_fields(key)
-            if len(key) == 1 and not isinstance(new_array.dtype, NestedDtype):
+            if len(key) == 1 and not isinstance(new_array.dtype.field_dtype(key[0]), NestedDtype):
                 # If only one field is requested, return it as a pd.Series
-                return pd.Series(new_array, index=self._series.index, name=self._series.name)
+                return self._series[key[0]]
             return NestedSeries(new_array, index=self._series.index, name=self._series.name)
 
         # If the key is a single string, return the flat series for that field

src/nested_pandas/series/nestedseries.py

@@ -50,8 +50,6 @@ def __getitem__(self, key):
         if not isinstance(self.dtype, NestedDtype):
             return super().__getitem__(key)
 
-        if not isinstance(self.dtype, NestedDtype):
-            return super().__getitem__(key)
         # Return a flatten series for a single field
         if isinstance(key, str) and key in self.fields:
             return self.nest[key]

tests/nested_pandas/series/test_accessor.py

@@ -769,6 +769,27 @@ def test___getitem___series_masking():
         _ = nf["nested"].nest[mask[0:23]]
 
 
+def test___getitem___single_list_field():
+    """Test that the .nest["field"] works for a single list field."""
+    struct_array = pa.StructArray.from_arrays(
+        arrays=[
+            pa.array([np.array([1, 2, 3]), np.array([4, 5, 6])]),
+            pa.array([np.array([6, 4, 2]), np.array([1, 2, 3])]),
+        ],
+        names=["a", "b"],
+    )
+    series = NestedSeries(struct_array, dtype=NestedDtype(struct_array.type), index=[5, 7])
+    assert_series_equal(
+        series.nest[["a"]],
+        pd.Series(
+            data=[1, 2, 3, 4, 5, 6],
+            index=[5, 5, 5, 7, 7, 7],
+            name="a",
+            dtype=pd.ArrowDtype(pa.int64()),
+        ),
+    )
+
+
 def test___setitem__():
     """Test that the .nest["field"] = ... works for a single field."""
     struct_array = pa.StructArray.from_arrays(