Deleting node of a way with 2 nodes doesn't get visualized

[geohacker]

@LanesGood I noticed that when we delete a node of a way with just 2 nodes, it doesn't show up in modifiedSharedWays layer or editedGeojson layer. Obviously this is because it's no longer a valid LineString. What do you think we should do in these cases?

[LanesGood]

@geohacker can the remaining node be converted to a singular node in the editedGeoJSON layer? If so, we could either save it as a single node point (not sure if there's a valid use case there), or implement a special style that indicates that this node needs another node to be saved. If not, then users should not be able to delete the last two nodes on any lineString.

[geohacker]

@LanesGood thank you. I inspected a bit more and this is a slightly complicated issue we need to address all the way from where the edits are created.

So few things to do:

• Remove deleted nodes from the map #303
• When it's the last but one node that's deleted, add the node to deleted nodes, but keep the geometry so we can visualize. We'd probably add a property called deleted to style this differently
• While creating the osm changeset, we'll manage this as a delete and not a modify. This will also modify any ways for which the deleted node is a part of.

cc @batpad

[geohacker]

The last thing to do in this workflow is to delete polygons with less than 3 nodes. Will close this once @batpad makes a PR for it.

[geohacker]

This is now addressed. To finish the styles we should do #318