[Feature Request] Support RELTYPE=CHILD for RELATED property

[Dexxes]

Hey,
I am writing a ToDo-List app for Windows (UWP) and I want to add a Subtask to an existing ToDo and for that I use the RELATED-TO property. I encounter a problem with the following VTODOs,
but i really need the RELATED-TO;RELTYPE=CHILD on the parent to determine its children...

Steps to reproduce

Put these to VTODOs in your calendar:

Supposed parent

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 4.1.6//EN
BEGIN:VTODO
SUMMARY:LIST1153
DTSTAMP:20200401T095356Z
UID:2fa55d38-006d-4010-aa3a-dc4f392cbccd
LAST-MODIFIED:20200401T095356Z
RELATED-TO;RELTYPE=CHILD:255ce6ca-fbae-4263-89c5-5743f8456b22
END:VTODO
END:VCALENDAR

Supposed child

BEGIN:VCALENDAR
VERSION:2.0
PRODID:Nextlist/Win
BEGIN:VTODO
SUMMARY:ELEM1326
DTSTAMP:20200401T112650Z
UID:255ce6ca-fbae-4263-89c5-5743f8456b22
LAST-MODIFIED:20200401T112650Z
END:VTODO
END:VCALENDAR

Expected behaviour

Correct subordination (PARENT-CHILD).

Actual behaviour

In the UI the parent is shown as subordinate although it's defined as superior in the code...

If I set RELATED-TO;RELTYPE=PARENT to the child VTODO and no property to the parent, the UI shows the subordination of the child correctly.

Nextcloud version: (see Nextcloud admin page)
18.0.2
Tasks version: (see Nextcloud apps page)
0.12.1

[raimund-schluessler]

In the UI the parent is shown as subordinate although it's defined as superior in the code...

If I set RELATED-TO;RELTYPE=PARENT to the child VTODO and no property to the parent, the UI shows the subordination of the child correctly.

Hm, this happens because we don't check the RELTYPE at the moment in https://github.com/nextcloud/tasks/blob/master/src/models/task.js#L347-L359 and https://github.com/nextcloud/tasks/blob/master/src/store/tasks.js#L68-L82 and just assume it is PARENT (the default as per https://tools.ietf.org/html/rfc5545#section-3.8.4.5). This is a bug on our side. As a fix, we should check that the RELTYPE is either not set or PARENT.

Also checking for RELTYPE CHILD needs a bit more work and I would consider this an enhancement, not a bug. We need to query for both PARENT and CHILD and also set both when a subtask is created (needs a request for both parent and child then, but I guess this would be ok).

[raimund-schluessler]

but i really need the RELATED-TO;RELTYPE=CHILD on the parent to determine its children...

What makes this a bit unattractive to use here is that when you have multiple childs specified you need to query them one by one (as far as I can tell at the moment). On the other hand, you can just request all VTODOs having RELATED-TO;RELTYPE=PARENT:255ce6ca-fbae-4263-89c5-5743f8456b22 set:

tasks/src/store/cdav-requests.js

Lines 59 to 70 in 3ae9306

	if (related) {
	query.children[0].children.push({
	name: [NS.IETF_CALDAV, 'prop-filter'],
	attributes: [
	['name', 'related-to'],
	],
	children: [{
	name: [NS.IETF_CALDAV, 'text-match'],
	value: related,
	}],
	})
	}

[Dexxes]

I see your point!

Right now I consider all VTODOS that have a description with “[ ] ” in it or have a RELTYPE=CHILD property as lists.

Maybe I have to rethink my model. Nonetheless it would be great if the RELTYPE=CHILD could be supported somehow …

[raimund-schluessler]

@Dexxes Please have a look at #972. The PR fixes the false evaluation of RELTYPE=CHILD as parent relation and prevents CHILD/SIBLING relations from being overwritten with a parent relation.

However, supporting CHILD relations for finding subtasks is more complicated and a bit of effort, so this is nothing for a bugfix PR / release.

[raimund-schluessler]

I will keep this issue open for tracking the support of RELTYPE=CHILD.