better protection of relation member order

[skyper]

Right now, you do not get any information if you split a way of an incompletely downloaded relation and it is not possible to determine the right position of the new member (before or after) in order to keep the order correct.

What I ask for:

1. a warning that user can intervene and manually download at least one more member.
   • in #18596 for type=route/multipolygon/relation a dialog was added but only if the relation is already known/downloaded.
     • the way to determine needed downloads need to be adjusted/changed, see #18863.
       • the neighbors in the relation's member list are used instead of the connected ways in data. see #18863:comment:35
     • support for more types is needed see #10808
       • is there any relation which does not benefit from preserving the order and has no special treatment.
2. an option to automatically download one or two members to determine the correct position.
   • introduced for type=route/multipolygon/boundary in #18596
     • does not work for all multipolygon see #18596#comment:60 and needs to be checked for boundary
3. a silent, temporally, partial download of the direct neighbors to automatically find the right position.
   • discussion?

Not sure if you really need both neighbors.

[skyper]

See #18596 for the first step.

[skyper]

In #18596 (r15943) the warning for some relation types were added including an option to download all members but only for already known/downloaded relations.

[JeroenHoek]

in #18596 the whole relation is downloaded

The patch introduced in #18596 only downloads the neighbouring members. I think the patch in JOSM r15943 and newer already does most of what you ask. I'm not sure what it is exactly you are requesting. Perhaps you could provide a use case?

[skyper]

• To solve 1. split way needs to check if all parent relations are known.
  ATM, this means that at least one child node with positive id needs to be within a download area bbox.
  Otherwise a least a warning should be displayed about possibly damaging unknown relations. Optional is the option to download one of the selected nodes or, maybe better, both end nodes, see 3.
• temporally downloads as in 3. are not used in JOSM, atm. There is no virtual/cache data layer. I thought of a solution to download the needed members only to determine the proper position in the member list and then purge/forget about them again

What steps will reproduce the problem?

1. Download a way with route relation
2. In relation list: download incomplete members
3. Select any node with parent way completely outside download area
4. split way

Here we need the warning. What happens afterwards is to be discussed and optional.

[skyper]

Ticket #8082 has been marked as a duplicate of this ticket.