fix bad datetime to str conversion in Series ctor _try_cast and add a test (#57512)

Author: ruimamaral

pandas/_libs/lib.pyx

@@ -757,7 +757,8 @@ cpdef ndarray[object] ensure_string_array(
             # dtype check to exclude DataFrame
             # GH#41409 TODO: not a great place for this
             out = arr.astype(str).astype(object)
-            out[arr.isna()] = na_value
+            if convert_na_value:
+                out[arr.isna()] = na_value
             return out
         arr = arr.to_numpy(dtype=object)
     elif not util.is_array(arr):

pandas/core/construction.py

@@ -800,6 +800,7 @@ def _try_cast(
             shape = arr.shape
             if arr.ndim > 1:
                 arr = arr.ravel()
+            arr = ensure_wrapped_if_datetimelike(arr)
         else:
             shape = (len(arr),)
         return lib.ensure_string_array(arr, convert_na_value=False, copy=copy).reshape(

pandas/tests/series/test_constructors.py

@@ -615,6 +615,23 @@ def test_constructor_maskedarray(self):
         )
         tm.assert_series_equal(result, expected)
 
+    @pytest.mark.parametrize("dtype", ["M8[s]", "M8[ms]", "M8[us]", "M8[ns]"])
+    def test_constructor_str_object_datetime_array(self, dtype):
+        # GH 57512
+        dt_arr = np.array(
+            [
+                "2024-01-03T00:00:00.000000000",
+                "2024-01-01T00:00:00.000000000",
+            ],
+            dtype=dtype,
+        )
+        result = Series(Series(dt_arr, dtype=str), dtype=dtype)
+        expected = Series(dt_arr, dtype=dtype)
+        tm.assert_series_equal(result, expected)
+
+        result = Series(Series(dt_arr, dtype=object), dtype=dtype)
+        tm.assert_series_equal(result, expected)
+
     def test_constructor_maskedarray_hardened(self):
         # Check numpy masked arrays with hard masks -- from GH24574
         data = ma.masked_all((3,), dtype=float).harden_mask()