Backport PR #52076 on branch 2.0.x (BUG: Fix regression when using Series with arrow string array)

pandas/_libs/lib.pyx

@@ -750,7 +750,6 @@ cpdef ndarray[object] ensure_string_array(
             out = arr.astype(str).astype(object)
             out[arr.isna()] = na_value
             return out
-
         arr = arr.to_numpy()
     elif not util.is_array(arr):
         arr = np.array(arr, dtype="object")

pandas/core/arrays/string_.py

@@ -351,6 +351,9 @@ def _from_sequence(cls, scalars, *, dtype: Dtype | None = None, copy: bool = Fal
             result[na_values] = libmissing.NA
 
         else:
+            if hasattr(scalars, "type"):
+                # pyarrow array
+                scalars = np.array(scalars)
             # convert non-na-likes to str, and nan-likes to StringDtype().na_value
             result = lib.ensure_string_array(scalars, na_value=libmissing.NA, copy=copy)
 

pandas/core/arrays/string_arrow.py

@@ -144,6 +144,8 @@ def _from_sequence(cls, scalars, dtype: Dtype | None = None, copy: bool = False)
             result = scalars._data
             result = lib.ensure_string_array(result, copy=copy, convert_na_value=False)
             return cls(pa.array(result, mask=na_values, type=pa.string()))
+        elif isinstance(scalars, (pa.Array, pa.ChunkedArray)):
+            return cls(pc.cast(scalars, pa.string()))
 
         # convert non-na-likes to str
         result = lib.ensure_string_array(scalars, copy=copy)

pandas/tests/extension/test_arrow.py

@@ -2324,3 +2324,11 @@ def test_boolean_reduce_series_all_null(all_boolean_reductions, skipna):
     else:
         expected = pd.NA
     assert result is expected
+
+
+@pytest.mark.parametrize("dtype", ["string", "string[pyarrow]"])
+def test_series_from_string_array(dtype):
+    arr = pa.array("the quick brown fox".split())
+    ser = pd.Series(arr, dtype=dtype)
+    expected = pd.Series(ArrowExtensionArray(arr), dtype=dtype)
+    tm.assert_series_equal(ser, expected)