Timestamp values: Remove the use of "naive" Python datetime objects

Python: Remove invocations to deprecated `datetime.utcfromtimestamp()`.

This is a possible BREAKING CHANGE about returned Python ``datetime``
objects:

> Removed the use of "naive" Python ``datetime`` objects, i.e. instances
without ``tzinfo`` attribute set.

When no ``time_zone`` information is specified when creating a database
connection or cursor, ``datetime`` objects will now use Coordinated
Universal Time (UTC), like CrateDB is storing timestamp values in this
format.

This update is coming from a deprecation of Python's
``datetime.utcfromtimestamp()``, which is effectively also phasing out
the use of "naive" timestamp objects in Python, in favor of using
timezone-aware objects, also to represent datetimes in UTC. It may be a
breaking change for some users of the library that don't expect to
receive "aware" ``datetime`` objects from now on.

DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).

CHANGES.txt

@@ -8,6 +8,19 @@ Unreleased
 - The SQLAlchemy dialect has been split off into the `sqlalchemy-cratedb`_
   package. See `Migrate from crate.client to sqlalchemy-cratedb`_ to learn
   about necessary migration steps.
+- Possible BREAKING CHANGE about returned Python ``datetime`` objects:
+  Removed the use of "naive" Python ``datetime`` objects, i.e. instances
+  without ``tzinfo`` attribute set.
+  When no ``time_zone`` information is specified when creating a database
+  connection or cursor, ``datetime`` objects will now use Coordinated
+  Universal Time (UTC), like CrateDB is storing timestamp values in this
+  format.
+  This update is coming from a deprecation of Python's
+  ``datetime.utcfromtimestamp()``, which is effectively also phasing out
+  the use of "naive" timestamp objects in Python, in favor of using
+  timezone-aware objects, also to represent datetimes in UTC. It may be a
+  breaking change for some users of the library that don't expect to
+  receive "aware" ``datetime`` objects from now on.
 - Configured DB API interface attribute ``threadsafety = 1``, which signals
   "Threads may share the module, but not connections."
 - Added ``error_trace`` to string representation of an Error to relay

docs/by-example/cursor.rst

@@ -333,7 +333,7 @@ types. Currently, this is implemented for the CrateDB data types ``IP`` and
     >>> cursor.execute('')
 
     >>> cursor.fetchone()
-    ['foo', IPv4Address('10.10.10.1'), datetime.datetime(2022, 7, 18, 18, 10, 36, 758000)]
+    ['foo', IPv4Address('10.10.10.1'), datetime.datetime(2022, 7, 18, 18, 10, 36, 758000, tzinfo=datetime.timezone.utc)]
 
 
 Custom data type conversion

src/crate/client/connection.py

@@ -119,11 +119,15 @@ def __init__(
             - ``zoneinfo.ZoneInfo("Australia/Sydney")``
             - ``+0530`` (UTC offset in string format)
 
+            The driver always returns timezone-"aware" `datetime` objects,
+            with their `tzinfo` attribute set.
+
             When `time_zone` is `None`, the returned `datetime` objects are
-            "naive", without any `tzinfo`, converted using ``datetime.utcfromtimestamp(...)``.
+            using Coordinated Universal Time (UTC), because CrateDB is storing
+            timestamp values in this format.
 
-            When `time_zone` is given, the returned `datetime` objects are "aware",
-            with `tzinfo` set, converted using ``datetime.fromtimestamp(..., tz=...)``.
+            When `time_zone` is given, the timestamp values will be transparently
+            converted from UTC to use the given time zone.
         """  # noqa: E501
 
         self._converter = converter

src/crate/client/converter.py

@@ -24,9 +24,9 @@
 https://crate.io/docs/crate/reference/en/latest/interfaces/http.html#column-types
 """
 
+import datetime as dt
 import ipaddress
 from copy import deepcopy
-from datetime import datetime
 from enum import Enum
 from typing import Any, Callable, Dict, List, Optional, Union
 
@@ -45,13 +45,13 @@ def _to_ipaddress(
     return ipaddress.ip_address(value)
 
 
-def _to_datetime(value: Optional[float]) -> Optional[datetime]:
+def _to_datetime(value: Optional[float]) -> Optional[dt.datetime]:
     """
     https://docs.python.org/3/library/datetime.html
     """
     if value is None:
         return None
-    return datetime.utcfromtimestamp(value / 1e3)
+    return dt.datetime.fromtimestamp(value / 1e3, tz=dt.timezone.utc)
 
 
 def _to_default(value: Optional[Any]) -> Optional[Any]:

src/crate/client/cursor.py

@@ -258,12 +258,15 @@ def time_zone(self, tz):
         - ``zoneinfo.ZoneInfo("Australia/Sydney")``
         - ``+0530`` (UTC offset in string format)
 
+        The driver always returns timezone-"aware" `datetime` objects,
+        with their `tzinfo` attribute set.
+
         When `time_zone` is `None`, the returned `datetime` objects are
-        "naive", without any `tzinfo`, converted using
-        `datetime.utcfromtimestamp(...)`.
+        using Coordinated Universal Time (UTC), because CrateDB is storing
+        timestamp values in this format.
 
-        When `time_zone` is given, the returned `datetime` objects are "aware",
-        with `tzinfo` set, converted by `datetime.fromtimestamp(..., tz=...)`.
+        When `time_zone` is given, the timestamp values will be transparently
+        converted from UTC to use the given time zone.
         """
 
         # Do nothing when time zone is reset.

tests/client/test_cursor.py

@@ -205,7 +205,16 @@ def test_execute_with_converter(self):
                 [
                     "foo",
                     IPv4Address("10.10.10.1"),
-                    datetime.datetime(2022, 7, 18, 18, 10, 36, 758000),
+                    datetime.datetime(
+                        2022,
+                        7,
+                        18,
+                        18,
+                        10,
+                        36,
+                        758000,
+                        tzinfo=datetime.timezone.utc,
+                    ),
                     6,
                 ],
                 [None, None, None, None],