BUG: Correct .type for pyarrow.map_ and pyarrow.struct types (pandas-dev#53344)

Author: mroeschke

doc/source/whatsnew/v2.0.2.rst

@@ -25,6 +25,7 @@ Fixed regressions
 
 Bug fixes
 ~~~~~~~~~
+- Bug in :class:`.arrays.ArrowExtensionArray` incorrectly assigning ``dict`` instead of ``list`` for ``.type`` with ``pyarrow.map_`` and raising a ``NotImplementedError`` with ``pyarrow.struct`` (:issue:`53328`)
 - Bug in :func:`api.interchange.from_dataframe` was raising ``IndexError`` on empty categorical data (:issue:`53077`)
 - Bug in :func:`api.interchange.from_dataframe` was returning :class:`DataFrame`'s of incorrect sizes when called on slices (:issue:`52824`)
 - Bug in :func:`api.interchange.from_dataframe` was unnecessarily raising on bitmasks (:issue:`49888`)

pandas/core/dtypes/dtypes.py

@@ -2053,6 +2053,8 @@ def type(self):
         elif pa.types.is_list(pa_type) or pa.types.is_large_list(pa_type):
             return list
         elif pa.types.is_map(pa_type):
+            return list
+        elif pa.types.is_struct(pa_type):
             return dict
         elif pa.types.is_null(pa_type):
             # TODO: None? pd.NA? pa.null?

pandas/tests/extension/test_arrow.py

@@ -1604,7 +1604,8 @@ def test_mode_dropna_false_mode_na(data):
         [pa.large_string(), str],
         [pa.list_(pa.int64()), list],
         [pa.large_list(pa.int64()), list],
-        [pa.map_(pa.string(), pa.int64()), dict],
+        [pa.map_(pa.string(), pa.int64()), list],
+        [pa.struct([("f1", pa.int8()), ("f2", pa.string())]), dict],
         [pa.dictionary(pa.int64(), pa.int64()), CategoricalDtypeType],
     ],
 )