BUG: Fix Series.str.contains with compiled regex on Arrow string dtype (#61942)

doc/source/whatsnew/v2.3.2.rst

@@ -26,6 +26,7 @@ Bug fixes
   "string" type in the JSON Table Schema for :class:`StringDtype` columns
   (:issue:`61889`)
 - Boolean operations (``|``, ``&``, ``^``) with bool-dtype objects on the left and :class:`StringDtype` objects on the right now cast the string to bool, with a deprecation warning (:issue:`60234`)
+- Fixed ``Series.str.contains`` with compiled regex on Arrow string dtype, which now correctly delegates to the object-dtype implementation. (:issue:`61942`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_232.contributors:

pandas/core/arrays/string_arrow.py

@@ -346,6 +346,8 @@ def _str_contains(
     ):
         if flags:
             return super()._str_contains(pat, case, flags, na, regex)
+        if isinstance(pat, re.Pattern):
+            pat = pat.pattern
 
         return ArrowStringArrayMixin._str_contains(self, pat, case, flags, na, regex)
 

pandas/tests/strings/test_find_replace.py

@@ -281,6 +281,21 @@ def test_contains_nan(any_string_dtype):
     tm.assert_series_equal(result, expected)
 
 
+def test_str_contains_compiled_regex_arrow_dtype(any_string_dtype):
+    # GH#61942
+    ser = Series(["foo", "bar", "baz"], dtype=any_string_dtype)
+    pat = re.compile("ba.")
+    result = ser.str.contains(pat)
+    # Determine expected dtype and values
+    expected_dtype = {
+        "string[pyarrow]": "bool[pyarrow]",
+        "string": "boolean",
+        "str": bool,
+    }.get(any_string_dtype, object)
+    expected = Series([False, True, True], dtype=expected_dtype)
+    tm.assert_series_equal(result, expected)
+
+
 # --------------------------------------------------------------------------------------
 # str.startswith
 # --------------------------------------------------------------------------------------