Work around a Pandas 0.23 bug

Work around an old time zone related bug
(pandas-dev/pandas#11736), which was fixed in
Pandas 0.24.

Author: aptiko

HISTORY.rst

@@ -2,6 +2,14 @@
 History
 =======
 
+4.0.2 (2022-11-27)
+==================
+
+- Worked around an old Pandas bug related to time zones
+  (https://github.com/pandas-dev/pandas/issues/11736) in order to
+  maintain compatibility with Pandas 0.23 (the bug was fixed in Pandas
+  0.24). 
+
 4.0.1 (2022-11-27)
 ==================
 

htimeseries/htimeseries.py

@@ -468,10 +468,11 @@ def _read_two_columns_from_stream(self, f):
             dtype={"value": np.float64},
         )
         result["flags"] = ""
+        self._ensure_pandas_0_23_compatibility(result)
         return result
 
     def _read_three_columns_from_stream(self, f):
-        return pd.read_csv(
+        result = pd.read_csv(
             f,
             parse_dates=[0],
             names=("date", "value", "flags"),
@@ -484,6 +485,16 @@ def _read_three_columns_from_stream(self, f):
             },
             dtype={"value": np.float64},
         )
+        self._ensure_pandas_0_23_compatibility(result)
+        return result
+
+    def _ensure_pandas_0_23_compatibility(self, result):
+        # Workaround for https://github.com/pandas-dev/pandas/issues/11736, which was
+        # fixed in 0.24.
+        if len(result) and result.index.tz is None:
+            result.index = result.index.tz_localize(dt.timezone.utc).tz_convert(
+                self.tzinfo
+            )
 
     def _check_there_are_no_duplicates(self, data):
         _check_timeseries_index_has_no_duplicates(

tests/test_htimeseries.py

@@ -432,6 +432,12 @@ def test_flags(self):
         expected = np.array(["", "MISS", "", "", ""])
         np.testing.assert_array_equal(self.ts.data.values[:, 1], expected)
 
+    def test_tz(self):
+        self.assertEqual(
+            self.ts.data.index.tz.utcoffset(dt.datetime(2000, 1, 1)),
+            dt.timedelta(hours=2),
+        )
+
 
 class HTimeseriesReadTwoColumnsTestCase(ReadFilelikeTestCaseBase, TestCase):
     def setUp(self):
@@ -447,6 +453,12 @@ def test_flags(self):
         expected = np.array(["", "", "", "", ""])
         np.testing.assert_array_equal(self.ts.data.values[:, 1], expected)
 
+    def test_tz(self):
+        self.assertEqual(
+            self.ts.data.index.tz.utcoffset(dt.datetime(2000, 1, 1)),
+            dt.timedelta(hours=2),
+        )
+
 
 class HTimeseriesReadMixOf2And3ColumnsTestCase(ReadFilelikeTestCaseBase, TestCase):
     def setUp(self):