JOSM should check relations for ways with no nodes (e.g., partially deleted ways)

[taylor.smock]

What steps will reproduce the problem?

1. Find a relation that (somehow) has a member that was deleted on openstreetmap.org
2. Edit the relation somewhere
3. Try to upload and get an error message complaining about a way not touched in that session (and not even downloaded) and a relation. Try updating the data, downloading the entire relation, and trying again.
4. Try to find the way under the assumption that we made the error in the local data.

What is the expected result?

One of the following:
1) Success on upload from a transparent autofix
2) A better error explanation (e.g., relation NUMBER has a deleted way NUMBER in it. Please try removing way NUMBER from relation NUMBER)
3) When searching for osm id's, if the id is not present in the current download window, ask if we want to look for parents of that id.

What happens instead?

It would be nice if there was a test that looked for (and possibly fixed) relations that referred to non-existent ways. The relation would have to be completely downloaded in order for this check to run, but it would be something.

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

There was a relation that had a way that had been deleted (​https://www.openstreetmap.org/relation/8429924) which was discovered when a separate person tried to upload a change that affected that relation. We initially tried running an update on all the data (which didn't work) to see if that fixed the problem, downloaded the entire relation.

The problem was introduced with ​https://www.openstreetmap.org/changeset/67205032 fixed in the next changset for that relation.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-02-02 21:01:18 +0100 (Sat, 02 Feb 2019)
Build-Date:2019-02-04 21:50:11
Revision:14760
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14760 en) Mac OS X 10.14.3
OS Build number: Mac OS X 10.14.3 (18D109)
Memory Usage: 1038 MB / 1820 MB (411 MB allocated, but free)
Java version: 1.8.0_201-b09, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: Display 69941064 2048x1152, Display 188916758 1920x1080
Maximum Screen Size: 2048x1152
VM arguments: [-Djava.security.policy=file:<java.home>/lib/security/javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>/bin, -Djava.security.manager, -Djnlpx.origFilenameArg=${HOME}/Desktop/josm.jnlp, -Djnlpx.remove=false, -Dsun.awt.warmup=true, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.heapsize=NULL,2048m, -Dmacosx.jnlpx.dock.name=JOSM, -Dmacosx.jnlpx.dock.icon=${HOME}/Library/Application Support/Oracle/Java/Deployment/cache/6.0/25/4c122699-47a1f67e.icns, -Djnlpx.jvm=“<java.home>/bin/java”]
Dataset consistency test: No problems found

Plugins:
+ Mapillary (v1.5.17)
+ apache-commons (34506)
+ apache-http (34632)
+ auto_tools (67)
+ buildings_tools (34867)
+ graphview (34867)
+ jna (34867)
+ log4j (34527)
+ osm-obj-info (51)
+ reverter (34867)
+ routing (34678)
+ turnrestrictions (34867)
+ utilsplugin2 (34867)

Map paint styles:
+ ${HOME}/Desktop/Map Styles/Kaart Styles 3.1.mapcss
+ https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
+ ${HOME}/Desktop/Map Styles/Overlapping Ways.mapcss

Validator rules:
+ https://raw.githubusercontent.com/KaartGroup/KaartValidator/master/kaart.mexicobrazil.validator.mapcss

Last errors/warnings:
- E: Error header: Precondition failed: Relation with id 8429924 cannot be saved due to Way with id 670515148
- W: Error header “Precondition failed: Relation with id 8429924 cannot be saved due to Way with id 670515148" did not match with an expected pattern
- E: org.openstreetmap.josm.io.OsmApiException: ResponseCode=412, Error Header=<Precondition failed: Relation with id 8429924 cannot be saved due to Way with id 670515148>
- E: Precondition violation - org.openstreetmap.josm.gui.widgets.HtmlPanel[,0,0,0x0,invalid,layout=java.awt.BorderLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=]
- W: Deleted or moved objects - <html>There are 349 objects in your local dataset which might be deleted on the server.<br>If you later try to delete or update them the server is likely to report a conflict.<br>Click <strong>Check on the server</strong> to check the state of these objects on the server.<br>Click <strong>Ignore</strong> to ignore.</html>
- W: Region [userProfile_BLOCK_v2] Problem verifying disk.  Message [org.openstreetmap.josm.plugins.mapillary.model.UserProfile]
- W: Region [userProfile_BLOCK_v2] Resetting cache
- W: Error when downloading user profile for user key ‘oLgvypHHMhcmxmwmVg-O5A’!: java.io.IOException: Server returned HTTP response code: 502 for URL: https://a.mapillary.com/v3/users/oLgvypHHMhcmxmwmVg-O5A?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz
- W: Could not read from URL https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=21.4743447%2C41.9927862%2C21.4761592%2C41.993754!: java.io.FileNotFoundException: https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=21.4743447%2C41.9927862%2C21.4761592%2C41.993754
- W: Could not read from URL https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=21.4645403%2C41.9772183%2C21.4754096%2C41.9937608!: java.io.FileNotFoundException: https://a.mapillary.com/v3/detections?client_id=T1Fzd20xZjdtR0s1VDk5OFNIOXpYdzoxNDYyOGRkYzUyYTFiMzgz&bbox=21.4645403%2C41.9772183%2C21.4754096%2C41.9937608