Split Object: Invalid, self-crossing closed ways created

[skyper]

What steps will reproduce the problem?

1. Have a closed way
2. Draw a new way between two nodes of the closed way crossing the closed way (area outline), example file​
3. Select the new unclosed way
4. Split Object

What is the expected result?

A notification about crossing ways and not action

What happens instead?

Two invald, self-crossing ways which additionally overlap are created

Please provide any additional information below. Attach a screenshot if possible.

See #21153 for another problem with overlapping result.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-07-21 20:57:29 +0200 (Wed, 21 Jul 2021)
Revision:18079
Build-Date:2021-07-22 01:31:13
URL:https://josm.openstreetmap.de/svn/trunk

Plugins:
+ utilsplugin2 (35792)

[GerdP]

I agree the split in the top-left example should be allowed.
I can add a check for self-intersection but I'm tempted to say "Garbage in -> Garbage out" for the other cases. JOSM allows to draw these invalid geometries as well and you only get a warning when running the validator.

[GerdP]

In 35833/osm:

see #21154
Don't deny split with message "The selected nodes can not be consecutive nodes in the object." when a splitway is used that has more than two nodes.

[GerdP]

add code to check for self-intersection or self-crossing ways

[GerdP]

We have similar code in core action AlignInCircleAction and CombineWayAction, I'll have a closer look how to reduce the code duplication. I am not sure if we should really deny the action or just show a warning.

[GerdP]

possible patch for JOSM core to perform geometry checks on a way

[GerdP]

With the core patch the code in the plugin could look like this:

            for (Way w : ds.getSelectedWays()) {
                if (!OsmValidator.validateGeometry(w, true))
                    break;
            }