I don’t know how far this is implemented on the CalDav synchronisation side already, but being able to view, edit and complete tasks on your phone would be immensely useful.
And being able to view them from the events view, just like calendar items would be great!
Some technical insights about tasks and synchronisation using CalDAV from the Open source parts of SailfishOS:
<c:comp-filter name="VEVENT"> where we actually ask the server to filter the returned components on events only. I’ve kept the filter up to now because changing it would mean that the synchronisation can be done also on tasks and notes, but these new tasks and notes will not be visible in any UI, just saved in the local database on device. And doing so will use code paths that have never been used yet, with potential issues. It would be a shame to fail synchronisation for something that is not visible.nemo-qml-plugin-calendar to do the job. And these bindings have been written for events only… There is a merge request to extend its capabilities to todos done by a community member: @rubdos. But it has never been accepted up to now. With it we would have possibilities to also display todos in QML.Which brings me to the last bit, that is not Open Source. The calendar application. It is mostly QML files, so community can try to contribute there with patches, but it’s not really convenient. But besides, what the community can do it to provide mockups and ideas on how the calendar app could be adjusted to display tasks. I’ve access to calendar application sources through an NDA, if I see nice mockups or ideas, I could try to implement them. The simpler the modifications are and the less intrusive to the current design, the higher is the possibility that they would be accepted. It happened already for instance with the new recursive options that have been proposed by @bongo and @peterleinchen (see this TJC thread) and that are now available in 3.4.0.
Finally, I think we may have the task displayed for almost free in event view as soon as QML files can cope with tasks (cf. my bullet on nemo-qml-plugin-calendar). The reminders are also for free since they are handled at mKCal level.
Nothing valuable here, I’m afraid, just what I’d like as the tasks display.
I’m not sure if the task of displaying tasks 
should be calendar’s job at all. For one, task are not necessarily tied to any given date. Still they can be displayed in calendar in pretty simple way:
Lifetime of a task (so, when should it be displayed):
Recurrence is a must (webOS, otherwise excellent as PIM, has no task recurrence. Useless).
Tricky part is ordering displayed tasks. I think that user-provided priority should be (at least by default) mixed with time-until-due, so effective sort priority should slowly rise as due date gets closer, maybe in non-linear way.
I don’t see a need to implement the tasks into calendar app. Even apple decides calendar and tasks into different apps while the sync protocol in the background is the same. Microsoft does the same in Windows 10: Events in calendar, tasks in To-Do.
I’d prefer it this way. So if I get @dcaliste right it would be easier to create a separate task app than implement tasks I to the calendar, correct? And even for those who prefer tasks in calendar app: right now we have no synced tasks app - getting one as standalone would be better than none…
Interesting post. I’ve begun creating an app for nextcloud tasks (which basically is caldav tasks aka VTODO’s). I posted earlier with some questions, and your post provides some insights in the answers to my questions.
I did look at nemo-qml-plugin-calendar, and concluded that it indeed does not support tasks, just events. When exploring the service by interacting over dbus I also seem to get only ‘get’ access to that service, is that expected? I’m probably missing some permission-related thing here, i’m quite the newbie in Sailfish development and still finding my way.
Anyway, implementing tasks into the calendar app is one way, but not optimal since it shuts out the community from working on it I guess. And I agree with @cryx that it makes a lot of sense to have one calendar app and another tasks app. I’m quite used to that seperation already, even in nextcloud they are different apps (using the same calendar storage backend). I’m hoping I can adapt the app i’m working on to use the nemo-qml-plugin-calendar if/when that provides read/write access to tasks, but for now the best seems to be to include the account handling / caldav interactions local to the app.
I really like the way its done in Nextcloud right now. Seperate Apps, but you can see Tasks in Calendar ond things from Deck in both calendar and tasks. But for editing/working it’s good to have different apps. Would like this in Sailfish too.
I’m on vacation at the moment. I cannot help you much. Next week we can interact directly if you wish so. For modifications you can do it via DBus, as for creation. I don’t have in mind the method though. It’s explained on old together.jolla.com
Since the last post is almost two years old: any news on this @dcaliste? I know you are very busy doing lot of great stuff 
Hello,
I, too, would love to have a CalDAV standards-compliant task app in Sailfish. On my libre Lineage OS device I use jtx Board because its standards-compliant and plays nicely with Thunderbird’s task management on my laptop. But I would prefer using Sailfish OS as my primary mobile, yet the lack of tasks integration holds me back.
I’m a little unclear on the above details in this thread: does a CLI interface already exist for tasks via Sailfish’s CalDAV sync, and we only need an app built?
A separate task app would be fine with me, though I could see an argument for calendar integration. But if the calendar is part of the closed-source bits, have there been any attempts to build an open calendar app with similar UX to the existing calendar? This would enable the community to improve it.
The same here. I’m waiting already 5 Years for caldav tasks 
+100