id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
10808	"JOSM breaks ""No U-Turn restriction"" relations when 'via' is a 'way', and relation isn't fully downloaded"	rickmastfan67	team	"Steps to reproduce:

1. Download the following way [osmwww:way/57375488], and make sure you download the ""parent relations"" as well
2. Split the way.

What happens:
The way is split, however, the 'no_u_turn' relation ([osmwww:relation/4247812]) now has 4 members because JOSM didn't realize that only one of the newly split ways should have been added.  Because of this, the relation now has 2 ways in the 'to' or 2 in the 'from' role depending on which type of way was split.

What should happen:
JOSM should properly give the 'no_u_turn' relations the proper segment of highway after the split like it does for other turn restriction relations.

This doesn't happen if the entire area is downloaded so that the relations are 'complete'.  But sometimes this isn't possible if there is a really long segment of highway and you just want to download a small area to split it up to add in a missing/new turn restriction at another intersection.

===

Now, if you were to try this with a relation that doesn't have a 'way' as the 'via', this problem doesn't happen.  If you try downloading Way '79335584' and split it at node '926517941', you will notice that the attached 'straight_only' relation is updated properly even though it's 'incomplete'.  Maybe that's because the 'via' node is downloaded.

===

Now, I don't know if this is possible to be fixed, but I have an idea that could fix it and it could be set aside for only when 'no_u_turn' restrictions are involved.  If when a way is being split and it has a 'no_u_turn' restriction relation(s) attached, JOSM should be 'forced' to download that entire relation automatically when the split happens if it's 'incomplete'.  This would become a 'fail-safe' for any relations that have the 'via' tag using a 'way'.  This would allow the no_u_turn relation to be properly updated like the 'Way 79335584' example I gave above.  It would prevent any mass breakage of already added 'no_u_turn' relations in the OSM database.

Or maybe have JOSM download the entire 'no_u_turn' restriction when you are downloading a section of data no matter what so you don't have to worry about it being incomplete and possibly breaking it?

What do you guys think?"	defect	new	major		Core	latest			simon04