Quests doing geometry checks are not shown again after undo

[riQQ]

How to Reproduce

• Move the map to https://www.openstreetmap.org/node/6437109524
• Answer the quest 'What kind of building entrance is this?' with any answer, e.g. 'Other entrance type'
• Undo the answer
• Quest doesn't appear again

Bonus

• Hard quitting the app and restarting doesn't help
• 'Scan for quest here' returns the quest

Expected Behavior
Quest comes back after undo

Versions affected
v47.1

[westnordost]

@matkoniecz this is your quest, could you look into that?

[matkoniecz]

Is there any other quest that is doing geometry checks and supporting undo? (entrance quest checks is it within building line and checks value of building= key and is also checking tags on footway line)

[westnordost]

"Is there a crossing? " for example.

All quests support undo.

[matkoniecz]

Looking at it:

    override fun isApplicableTo(element: Element): Boolean? =
        if (element !is Node || element.tags.isNotEmpty()) false else null

it seems that undone crossing quest will also disappear.

I also tested it and it actually happens: I solved quest, undid it and it has become missing.

So fixing this would require implementing doing geometry checks on undo.

[westnordost]

Eh, what are you on about? Don't you know what happens when that function returns null?

[Helium314]

Issue is that this is not valid for crossing and entrance quests:

StreetComplete/app/src/main/java/de/westnordost/streetcomplete/data/osm/osmquests/OsmQuestController.kt

Lines 202 to 204 in 2499d77

	/* shortcut: if the element has no tags, it is just part of the geometry of another
	* element, so no need to check for quests for that element */
	if (element.tags.isEmpty()) return@async null

[westnordost]

Hm I think this can be removed without replacement, after all the quest filters already filter out elements with no tags fast

[westnordost]

Thanks for the find, @Helium314

[matkoniecz]

Eh, what are you on about? Don't you know what happens when that function returns null?

apparently not! I thought that it means that undo was not supported - but was unsure, so I tested it which seemed to confirm it.