Single day event with "open end" checked still needs a end date

[TimoBroeskamp]

Describe the bug
When creating a single-day event with the "open end" option checked, the end date field is correctly hidden from the UI — but form validation still requires it, preventing submission. Since the end date selector is not visible, users have to uncheck the "open end" option to set a date that is after the start of the event just to check it again and save it.

To Reproduce
Steps to reproduce the behavior:

1. Create an event
2. Give the event a title
3. Set a starting date for the event
4. Check the "whole day" selector
5. Check the "open end" selector
6. Save the event

Expected behavior
I expect be able to save the event when I set it to "whole day" and "open end" and don't need to enter an end date.

Screenshots

Software (please complete the following information):

• OS: Ubuntu
• Browser: Chrome
• Volto Version: Volto 19.0.0-alpha.27
• Plone Version: 6.1.4
• Plone REST API Version: 9.15.4

Additional context
Add any other context about the problem here.

[stevepiercy]

Confirmed with modified instructions:

3.b. Clear the Event Ends field.

The fix is to comply with the iCalendar specification for VEVENT:

For cases where a "VEVENT" calendar component specifies a "DTSTART" property with a DATE value type but no "DTEND" nor "DURATION" property, the event's duration is taken to be one day. For cases where a "VEVENT" calendar component specifies a "DTSTART" property with a DATE-TIME value type but no "DTEND" property, the event ends on the same calendar date and time of day specified by the "DTSTART" property.

In other words, if someone clears the Event Ends field and checks Open End, then the same date or datetime should be populated in the Event Ends field before submission.

Would you like to submit a PR?

[TimoBroeskamp]

Yeah I will work on that.

[jackahl]

Confirmed with modified instructions:

3.b. Clear the Event Ends field.

The fix is to comply with the iCalendar specification for VEVENT:

For cases where a "VEVENT" calendar component specifies a "DTSTART" property with a DATE value type but no "DTEND" nor "DURATION" property, the event's duration is taken to be one day. For cases where a "VEVENT" calendar component specifies a "DTSTART" property with a DATE-TIME value type but no "DTEND" property, the event ends on the same calendar date and time of day specified by the "DTSTART" property.

In other words, if someone clears the Event Ends field and checks Open End, then the same date or datetime should be populated in the Event Ends field before submission.

Would you like to submit a PR?

@stevepiercy just saw your comment here. Do I understand this correctly, that the end value should be the same as the start value in the case of open end?

[stevepiercy]

@jackahl yes, according to the RFC I cited. You're welcome to double-check my interpretation.

I would also say that the implementation in Volto and in plone.restapi should be consistent with the RFC.

[stevepiercy]

It appears that the underlying Python library doesn't take this into account either. See collective/icalendar#1275.

[jackahl]

@stevepiercy ok, makes sense to me. Just took me a couple of reads to actually get what the RFC is actually saying. From my tests p.restapi and should accept requests with same start and end datetime.
@TimoBroeskamp then please amend your current change here to only allow the same datetime as end as the start datetime.
Then you can continue by adding a logic that automatically sets the end field = start in the request when "open end" is selected