Fix #28104 - CalDav support for floating datetimes (#28123)

* Fix #28104 - CalDav support for floating datetimes

Timzones are optional in CalDav

It is possible that an entry contains neither a TZID, nor is an UTC time.
When this is the case, it should be treated as a floating date-time value,
which represent the same hour, minute, and second value regardless of which
time zone is currently being observed.

For Home-Assistant the correct timezone therefore is whatever is configured
as local time in the settings.

See https://www.kanzaki.com/docs/ical/dateTime.html

* Revert "Fix #28104 - CalDav support for floating datetimes"

This reverts commit cf32a6e39058e340816ae1e3ebd4a2c236b91964.

* add test case: floating events fail with error without patch

* Fix #28104 - CalDav support for floating datetimes

Timzones are optional in CalDav

It is possible that an entry contains neither a TZID, nor is an UTC time.
When this is the case, it should be treated as a floating date-time value,
which represent the same hour, minute, and second value regardless of which
time zone is currently being observed.

For Home-Assistant the correct timezone therefore is whatever is configured
as local time in the settings.

See https://www.kanzaki.com/docs/ical/dateTime.html

* style fix

homeassistant/components/caldav/calendar.py

@@ -278,6 +278,10 @@ class WebDavCalendarData:
     def to_datetime(obj):
         """Return a datetime."""
         if isinstance(obj, datetime):
+            if obj.tzinfo is None:
+                # floating value, not bound to any time zone in particular
+                # represent same time regardless of which time zone is currently being observed
+                return obj.replace(tzinfo=dt.DEFAULT_TIME_ZONE)
             return obj
         return dt.as_local(dt.dt.datetime.combine(obj, dt.dt.time.min))
 

tests/components/caldav/test_calendar.py

@@ -111,6 +111,19 @@ LOCATION:San Francisco
 DESCRIPTION:Sunny day
 END:VEVENT
 END:VCALENDAR
+""",
+    """BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Global Corp.//CalDAV Client//EN
+BEGIN:VEVENT
+UID:8
+DTSTART:20171127T190000
+DTEND:20171127T200000
+SUMMARY:This is a floating Event
+LOCATION:Hamburg
+DESCRIPTION:What a day
+END:VEVENT
+END:VCALENDAR
 """,
 ]
 
@@ -292,6 +305,29 @@ async def test_ongoing_event_different_tz(mock_now, hass, calendar):
     }
 
 
+@patch("homeassistant.util.dt.now", return_value=_local_datetime(19, 10))
+async def test_ongoing_floating_event_returned(mock_now, hass, calendar):
+    """Test that floating events without timezones work."""
+    assert await async_setup_component(hass, "calendar", {"calendar": CALDAV_CONFIG})
+    await hass.async_block_till_done()
+
+    state = hass.states.get("calendar.private")
+    print(dt.DEFAULT_TIME_ZONE)
+    print(state)
+    assert state.name == calendar.name
+    assert state.state == STATE_ON
+    assert dict(state.attributes) == {
+        "friendly_name": "Private",
+        "message": "This is a floating Event",
+        "all_day": False,
+        "offset_reached": False,
+        "start_time": "2017-11-27 19:00:00",
+        "end_time": "2017-11-27 20:00:00",
+        "location": "Hamburg",
+        "description": "What a day",
+    }
+
+
 @patch("homeassistant.util.dt.now", return_value=_local_datetime(8, 30))
 async def test_ongoing_event_with_offset(mock_now, hass, calendar):
     """Test that the offset is taken into account."""