BUG: Fix comparison between nullable int and string (pandas-dev#28945)

doc/source/whatsnew/v1.0.0.rst

@@ -840,6 +840,7 @@ ExtensionArray
 ^^^^^^^^^^^^^^
 
 - Bug in :class:`arrays.PandasArray` when setting a scalar string (:issue:`28118`, :issue:`28150`).
+- Bug where nullable integers could not be compared to strings (:issue:`28930`)
 -
 
 

pandas/conftest.py

@@ -654,6 +654,24 @@ def any_int_dtype(request):
     return request.param
 
 
+@pytest.fixture(params=ALL_EA_INT_DTYPES)
+def any_nullable_int_dtype(request):
+    """
+    Parameterized fixture for any nullable integer dtype.
+
+    * 'UInt8'
+    * 'Int8'
+    * 'UInt16'
+    * 'Int16'
+    * 'UInt32'
+    * 'Int32'
+    * 'UInt64'
+    * 'Int64'
+    """
+
+    return request.param
+
+
 @pytest.fixture(params=ALL_REAL_DTYPES)
 def any_real_dtype(request):
     """

pandas/core/arrays/integer.py

@@ -26,6 +26,7 @@
 from pandas.core import nanops, ops
 from pandas.core.algorithms import take
 from pandas.core.arrays import ExtensionArray, ExtensionOpsMixin
+from pandas.core.ops import invalid_comparison
 from pandas.core.ops.common import unpack_zerodim_and_defer
 from pandas.core.tools.numeric import to_numeric
 
@@ -646,7 +647,11 @@ def cmp_method(self, other):
             with warnings.catch_warnings():
                 warnings.filterwarnings("ignore", "elementwise", FutureWarning)
                 with np.errstate(all="ignore"):
-                    result = op(self._data, other)
+                    method = getattr(self._data, f"__{op_name}__")
+                    result = method(other)
+
+                    if result is NotImplemented:
+                        result = invalid_comparison(self._data, other, op)
 
             # nans propagate
             if mask is None:

pandas/tests/extension/test_integer.py

@@ -168,6 +168,27 @@ def check_opname(self, s, op_name, other, exc=None):
     def _compare_other(self, s, data, op_name, other):
         self.check_opname(s, op_name, other)
 
+    def test_compare_to_string(self, any_nullable_int_dtype):
+        # GH 28930
+        s = pd.Series([1, None], dtype=any_nullable_int_dtype)
+        result = s == "a"
+        expected = pd.Series([False, False])
+
+        self.assert_series_equal(result, expected)
+
+    def test_compare_to_int(self, any_nullable_int_dtype, all_compare_operators):
+        # GH 28930
+        s1 = pd.Series([1, 2, 3], dtype=any_nullable_int_dtype)
+        s2 = pd.Series([1, 2, 3], dtype="int")
+
+        method = getattr(s1, all_compare_operators)
+        result = method(2)
+
+        method = getattr(s2, all_compare_operators)
+        expected = method(2)
+
+        self.assert_series_equal(result, expected)
+
 
 class TestInterface(base.BaseInterfaceTests):
     pass