Implement interface tests

Author: WillAyd

pandas/core/arrays/list_.py

@@ -54,6 +54,8 @@ class ListDtype(ArrowDtype):
     An ExtensionDtype suitable for storing homogeneous lists of data.
     """
 
+    _is_immutable = True  # TODO(wayd): should we allow mutability?
+
     def __init__(self, value_dtype: pa.DataType) -> None:
         super().__init__(pa.large_list(value_dtype))
 
@@ -211,3 +213,19 @@ def astype(self, dtype: AstypeArg, copy: bool = True) -> ArrayLike:
             return np.array([str(x) for x in self], dtype=dtype)
 
         return super().astype(dtype, copy)
+
+    def __eq__(self, other):
+        if isinstance(other, (pa.ListScalar, pa.LargeListScalar)):
+            from pandas.arrays import BooleanArray
+
+            # TODO: pyarrow.compute does not implement broadcasting equality
+            # for an array of lists to a listscalar
+            # TODO: pyarrow doesn't compare missing values as missing???
+            # arr = pa.array([1, 2, None])
+            # pc.equal(arr, arr[2]) returns all nulls but
+            # arr[2] == arr[2] returns True
+            mask = np.array([False] * len(self))
+            values = np.array([x == other for x in self._pa_array])
+            return BooleanArray(values, mask)
+
+        return super().__eq__(other)

pandas/tests/extension/list/test_list.py

@@ -17,6 +17,7 @@
 from pandas.tests.extension.base.dtype import BaseDtypeTests
 from pandas.tests.extension.base.groupby import BaseGroupbyTests
 from pandas.tests.extension.base.index import BaseIndexTests
+from pandas.tests.extension.base.interface import BaseInterfaceTests
 from pandas.tests.extension.base.missing import BaseMissingTests
 from pandas.tests.extension.base.ops import (  # noqa: F401
     BaseArithmeticOpsTests,
@@ -70,7 +71,7 @@ class TestListArray(
     # BaseGetitemTests,
     BaseGroupbyTests,
     BaseIndexTests,
-    # BaseInterfaceTests,
+    BaseInterfaceTests,
     # BaseParsingTests,
     # BaseMethodsTests,
     BaseMissingTests,
@@ -112,6 +113,9 @@ def test_groupby_extension_transform(self, data_for_grouping):
     def test_groupby_extension_apply(self, data_for_grouping, groupby_apply_op):
         pytest.skip(reason="ListArray does not implement dictionary_encode")
 
+    def test_array_interface(self, data):
+        pytest.skip(reason="ListArrayScalar does not compare to numpy object-dtype")
+
 
 def test_to_csv(data):
     # https://github.com/pandas-dev/pandas/issues/28840