yaml2ics: Allow a "timezone" option within each event. (#22)

* yaml2ics: Allow a "timezone" option within each event.

- I at first tried using the yaml datetime "+03:00" explicit offset.
  But, this created an output that worked in Google
  Calendar/Thunderbird, but not office 365 cloud.  The problem seems
  to relate to the quoting of `"UTC +03:00"` in one place but not the
  other (and, as it turns out, it didn't work with either quotes
  there, or no quotes there!)
- I had made the idea in this PR earlier, but didn't submit it because
  "less is more".  But now this seems simpler (and more explicit
  somehow).
- Changes are minimal and it just worked in one of my test casse.
  There is no effect if 'timezone' is not given in an event.
- Review: decide if this is a good idea or not.  Is there any simpler
  way to implement it?

* .pre-commit-config: Bump black (click incompatibility)

- As described at the top of psf/black#2964

Author: rkdarst

.pre-commit-config.yaml

@@ -9,7 +9,7 @@ repos:
       - id: end-of-file-fixer
       - id: trailing-whitespace
   - repo: https://github.com/psf/black
-    rev: 22.1.0
+    rev: 22.3.0
     hooks:
       - id: black
   - repo: https://gitlab.com/pycqa/flake8

example/test_calendar.yaml

@@ -15,6 +15,11 @@ events:
     location: |
       Office 224, Monolith Bldg, Office Block C
 
+  - summary: 15-minute meeting with timezone
+    timezone: America/New_York  # symbolic timezone offset
+    begin: 2021-09-23 15:00:00
+    end: 2021-09-23 15:30:00
+
   - summary: Half-an-hour meeting
     begin: 2021-09-23 15:00:00 -07:00  # explicit timezone offset
     end: 2021-09-23 15:30:00 -07:00    # explicit timezone offset

tests/test_calendar.py

@@ -77,6 +77,41 @@ def test_calendar_default_timezone():
     assert "DTSTART:20220131T220000Z"  # 1 feb
 
 
+def test_calendar_event_different_timezone():
+    # This test is just like the one above, but with the timezone definition
+    # locations changed.
+    cal = files_to_calendar(
+        [
+            iowrap(
+                """
+            timezone: America/New_York
+
+            events:
+              - summary: New year's day
+                timezone: Europe/Helsinki
+                begin: 2022-01-01 00:00:00
+                duration: {hours: 1}
+            """
+            )
+        ]
+    )
+    cal_str = cal.serialize()
+    assert cal_str.startswith("BEGIN:VCALENDAR")
+    assert "SUMMARY:New year" in cal_str
+    # It is possible that the ics-py TZID string changes, but hopefully this
+    # substring is fairly safe to test against.
+    assert "Europe/Helsinki:20220101T000000" in cal_str
+    assert "America/New_York" not in cal_str
+
+    # Test again by normalizing to UTC.  Helsinki is two hours ahead, so the
+    # times should be 22:00:00.
+    cal.normalize(datetime.timezone.utc)
+    cal_norm_str = cal.serialize()  # noqa: F841
+    # 1 Feb midnight
+    assert "DTSTART:20211231T220000Z"  # 1 jan
+    assert "DTSTART:20220131T220000Z"  # 1 feb
+
+
 def test_calendar_name():
     cal = files_to_calendar(
         [

yaml2ics.py

@@ -28,6 +28,8 @@
 def event_from_yaml(event_yaml: dict, tz: tzinfo = None) -> ics.Event:
     d = event_yaml
     repeat = d.pop("repeat", None)
+    if "timezone" in d:
+        tz = gettz(d.pop("timezone"))
 
     # Strip all string values, since they often end on `\n`
     for key in d: