Can't create a new master relation for new relations

[KenAlin]

Hi,

I wanted to add a bus route is OpenStreetMap today using iD, but I got the following error message :

Placeholder Relation not found for reference -3 in relation -2. (Server returned error code 400.)

Here is what I tried to do :

• Create a relation for a direction (A -> B)
• Create an other relation for the other direction (B -> A)
• Create a relation (route master) containing the two previous relations
• Mapping
• Sending to the server ... uh oh ...

Here is what I've done :

• Delete route master
• Sending to the server ... it worked !
• Finally, re-creating the route master in a new changeset (it worked too)

I don't really know what happened, nor why it worked when deleting the route master ... Hope this helped.

[bhousel]

Thanks! It does sound like a bug..

[mstn]

Hi, in order to reproduce this bug

curl -u [USERNAME]:[PASSWORD]  -X POST -d @payload.xml http://localhost:3000/api/0.6/changeset/[CHANGESET_ID]/upload

where payload.xml is

<?xml version="1.0" encoding="UTF-8"?>
<osmChange version="0.6" generator="iD">
   <create>
      <node id="-5" lon="11.625506992810122" lat="46.866699181636555" version="0" changeset="3">
         <tag k="highway" v="bus_stop" />
      </node>
      <node id="-6" lon="11.62686047585252" lat="46.86730122861715" version="0" changeset="3">
         <tag k="highway" v="bus_stop" />
      </node>
      <relation id="-2" version="0" changeset="3">
         <member type="node" role="" ref="-5" />
         <tag k="type" v="route" />
         <tag k="name" v="AtoB" />
      </relation>
      <relation id="-3" version="0" changeset="3">
         <member type="relation" role="" ref="-2" />
         <member type="relation" role="" ref="-4" />
         <tag k="type" v="route_master" />
         <tag k="name" v="master" />
      </relation>
      <relation id="-4" version="0" changeset="3">
         <member type="node" role="" ref="-6" />
         <tag k="type" v="route" />
         <tag k="name" v="BtoA" />
      </relation>
   </create>
   <modify />
   <delete if-unused="true" />
</osmChange>

The output is

Placeholder Relation not found for reference -4 in relation -3.

The problem is that the master relation (-3) that contains the two children (-2 and -4) should be listed at the end of the create tag. If you edit payload.xml by hand, it works.

[pnorman]

if that payload.xml is generated by iD, then it's in error. And has way too many significant figures on the nodes.

[mstn]

Yes, it is generated by iD (just copied and pasted from network tab).

[bhousel]

per openstreetmap/openstreetmap-website#1465 (comment)
let's:

• reorder the relations in the changeset so that children appear in the file before their parents
• add some checks throughout iD to prevent users from creating circular relation graphs

[pnorman]

If you take the sequence of actions taken by a user and turn it into a diff it should always work, but it will be too verbose (e.g. create node, modify node to add tag, modify node to change location instead of one create node with tag at second location).

So it should be possible to do this by changing the formation of the osmChange rather than re-ordering, but I don't know which is easier.