[WIP] as_vevent: use vDDDTypes instead of explicit date/datetime type

[wichmannpas]

This fixes a problem when using the decoded method.
E.g., event.decoded('dtstart') fails with an exception:

  File ".../.pyenv/lib/python3.7/site-packages/icalendar/cal.py", line 237, in decoded
    return self._decode(name, value)
  File ".../.pyenv/lib/python3.7/site-packages/icalendar/cal.py", line 220, in _decode
    decoded = types_factory.from_ical(name, value)
  File ".../.pyenv/lib/python3.7/site-packages/icalendar/prop.py", line 1042, in from_ical
    decoded = type_class.from_ical(value)
  File ".../.pyenv/lib/python3.7/site-packages/icalendar/prop.py", line 334, in from_ical
    u = ical.upper()

This is due to a type inconsistency between the event created by this
package and the type that icalendar expects.

Another (ugly) workaround for this problem (if this patch was not
applied) would be to convert the event to ical and parse it back using
icalendar, which repairs the dtstart type inconsistency as well (e.g.,
something like `event = icalendar.Calendar.from_ical(event.to_ical())``

[wichmannpas]

Consider this pull request rather as half an issue: I am not sure whether the tests are indeed supposed to force the specific date/datetime types (which do not seem to be used in that way by icalendar at that level). Feel free to edit the tests within this pull request (or find another solution to the issue).

[niccokunzmann]

@wichmannpas Thanks for reporting this - I did not encounter this so I am happy to see that you know about this. Can you add a source code - or best a test - which fails/breaks? Something that can be reproduced that is broken?

I am not sure whether the tests are indeed supposed to force the specific date/datetime types (which do not seem to be used in that way by icalendar at that level).
I added this because there are effects I cannot estimate: timezone/no timezone in the calendar, date/datetime, RDATE, EXRULE, ... So, I tested that if the event has a date as a start, the repetition also has a date and not a date+time.

[niccokunzmann]

To use these changes, the tests would also need to be changed. I did not really know about the vDDDType. I evaluate:

class vDDDTypes(object):
    """A combined Datetime, Date or Duration parser/generator. Their format
    cannot be confused, and often values can be of either types.
    So this is practical.
    """

https://github.com/collective/icalendar/blob/2b56bc4ee7e90fe7204174f5c8c4b48dc2de8636/src/icalendar/prop.py#L286

I think: If the tests can be changed this way: each event in the test is converted to bytes and back and then, the type is tested, then, they should work without further changes and this is quite nice and practical.

[niccokunzmann]

What do you think?

• note: unused method would also need to be removed.

[wichmannpas]

Thanks for the feedback, I will try to have a look at the tests and add a test case for the problem in the next weeks.

[niccokunzmann]

@wichmannpas Thanks! I could remove some unnecessary tests.