Warn users when joining ways leads to broken relations or multi-value tags

[thomaskonrad]

Hi,

I've recently reverted multiple changes of a user who joined several ways where one way was part of a relation and the other was not (this broke the relation). Moreover, the ways had different "highway" tag values ("unclassified" and "residential") which lead to the tag value being "unclassified;residential". The same happened with "maxspeed" tags; the final value was e.g. "30;50". Such multi-value tags do not make any sense for many widespread tags. The said way also disappeared from the Mapnik rendering because the renderer was confused (of course).

So it would be great if the user would be warned if the join of two ways leads to either 1) changed / broken relations or 2) tags with multiple values where this does not make sense (which is the case most of the time IMHO). I think these two cases should be pretty easy to detect programmatically (although I have to admin that I haven't looked into the iD code yet).

Thanks
Thomas

[jfirebaugh]

Duplicate of #2358 / #908.