FIX: Parsing dates and dtype in read_csv (issue pandas-dev#34066)

Author: mproszewska

pandas/io/parsers.py

@@ -1708,7 +1708,9 @@ def _convert_to_ndarrays(
         result = {}
         for c, values in dct.items():
             conv_f = None if converters is None else converters.get(c, None)
-            if isinstance(dtypes, dict):
+            if values.dtype != object:
+                cast_type = values.dtype
+            elif isinstance(dtypes, dict):
                 cast_type = dtypes.get(c, None)
             else:
                 # single dtype or None
@@ -3264,6 +3266,9 @@ def _make_date_converter(
 ):
     def converter(*date_cols):
         if date_parser is None:
+            date_cols = tuple(
+                [x if isinstance(x, np.ndarray) else x.to_numpy() for x in date_cols]
+            )
             strs = parsing.concat_date_cols(date_cols)
 
             try:

pandas/tests/io/parser/test_common.py

@@ -2135,3 +2135,17 @@ def test_no_header_two_extra_columns(all_parsers):
     parser = all_parsers
     df = parser.read_csv(stream, header=None, names=column_names, index_col=False)
     tm.assert_frame_equal(df, ref)
+
+
+def test_dtype_with_parse_dates(all_parsers):
+    # GH 34066
+    parser = all_parsers
+    data = """
+a,b
+1,2020-05-23 01:00:00"""
+    expected = DataFrame(
+        [["1", "2020-05-23 01:00:00"]], columns=["a", "b"], dtype="string"
+    )
+    expected = expected.astype({"b": np.datetime64})
+    df = parser.read_csv(StringIO(data), dtype="string", parse_dates=["b"])
+    tm.assert_frame_equal(df, expected)