Address review

Author: mroeschke

Diff for: doc/source/whatsnew/v0.23.0.txt

@@ -586,7 +586,7 @@ Datetimelike API Changes
 - Operations between a :class:`Series` with dtype ``dtype='datetime64[ns]'`` and a :class:`PeriodIndex` will correctly raises ``TypeError`` (:issue:`18850`)
 - Subtraction of :class:`Series` with timezone-aware ``dtype='datetime64[ns]'`` with mis-matched timezones will raise ``TypeError`` instead of ``ValueError`` (:issue:`18817`)
 - :func:`pandas.merge` provides a more informative error message when trying to merge on timezone-aware and timezone-naive columns (:issue:`15800`)
-- :class:`Timestamp` constructor now accepts a `nanosecond` keyword or positional argument (:issue:`18898`)
+- :class:`Timestamp` constructor now accepts a ``nanosecond`` keyword or positional argument (:issue:`18898`)
 
 .. _whatsnew_0230.api.other:
 

Diff for: pandas/_libs/tslibs/timestamps.pyx

@@ -423,10 +423,12 @@ class Timestamp(_Timestamp):
         example, 's' means seconds and 'ms' means milliseconds.
     year, month, day : int
         .. versionadded:: 0.19.0
-    hour, minute, second, microsecond, nanosecond : int, optional, default 0
+    hour, minute, second, microsecond : int, optional, default 0
         .. versionadded:: 0.19.0
     tzinfo : datetime.tzinfo, optional, default None
         .. versionadded:: 0.19.0
+    nanosecond : int, optional, default 0
+        .. versionadded:: 0.23.0
 
     Notes
     -----
@@ -588,7 +590,16 @@ class Timestamp(_Timestamp):
             elif tz is not None:
                 raise ValueError('Can provide at most one of tz, tzinfo')
 
-        if ts_input is _no_input:
+        if is_string_object(ts_input):
+            # User passed a date string to parse.
+            # Check that the user didn't also pass a date attribute kwarg.
+            date_attrs = [year, month, day, hour, minute, second, microsecond,
+                          nanosecond]
+            if any(arg is not None for arg in date_attrs):
+                raise ValueError('Cannot pass a date attribute keyword '
+                                 'argument when passing a date string')
+
+        elif ts_input is _no_input:
             # User passed keyword arguments.
             if tz is None:
                 # Handle the case where the user passes `tz` and not `tzinfo`

Diff for: pandas/tests/scalar/timestamp/test_timestamp.py

@@ -397,6 +397,13 @@ def test_constructor_nanosecond(self, result):
         expected = expected + Timedelta(nanoseconds=1)
         assert result == expected
 
+    @pytest.mark.parametrize('arg', ['year', 'month', 'day', 'hour', 'minute',
+                                     'second', 'microsecond', 'nanosecond'])
+    def test_invalid_date_kwarg_with_string_input(self, arg):
+        kwarg = {arg: 1}
+        with pytest.raises(ValueError):
+            ts = Timestamp('2010-10-10 12:59:59.999999999', **kwarg)
+
     def test_out_of_bounds_value(self):
         one_us = np.timedelta64(1).astype('timedelta64[us]')