NPE at AbstractDownloadStrategy.getExisting()

[gaben]

What steps will reproduce the problem?

:(

What is the expected result?

What happens instead?

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

I edited some Overpass output further processed in a Python script then opened in JOSM.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2023-03-23 18:00:59 +0100 (Thu, 23 Mar 2023)
Build-Date:2023-03-24 02:30:58
Revision:18699
Relative:URL: ^/trunk

Identification: JOSM/1.5 (18699 hu) Windows 10 64-Bit
OS Build number: Windows 10 Pro for Workstations 2009 (19045)
Memory Usage: 1171 MB / 7266 MB (507 MB allocated, but free)
Java version: 1.8.0_361-b09, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1200 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1200
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1250
System property sun.jnu.encoding: Cp1250
Locale info: hu_HU
Numbers with default locale: 1234567890 -> 1234567890
VM arguments: [-Djava.security.manager, -Djnlp.application.href=https://josm.openstreetmap.de/download/josm-latest.jnlp, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlp.tk=awt, -Djnlpx.jvm=<java.home>\bin\javaw.exe, -Djnlpx.splashport=56957, -Djnlpx.home=<java.home>\bin, -Djnlpx.remove=false, -Djnlpx.offline=false, -Djnlpx.relaunch=true, -Djnlpx.session.data=%UserProfile%\AppData\Local\Temp\session2672114055966594230, -Djnlpx.heapsize=NULL,NULL, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.origFilenameArg=%UserProfile%\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\31\583aa85f-6ec62164]

Plugins:
+ AddrInterpolation (36011)
+ FastDraw (36057)
+ OpeningHoursEditor (35924)
+ apache-commons (36034)
+ buildings_tools (36011)
+ continuosDownload (105)
+ ejml (35924)
+ geotools (36028)
+ gridify (1606242219)
+ jackson (36034)
+ jaxb (35952)
+ jts (36004)
+ opendata (36025)
+ pbf (36034)
+ phonenumber (0.16.1)
+ pt_assistant (2.1.15-19-g9aeec3c-SNAPSHOT)
+ reverter (36043)
+ tageditor (36011)
+ turnlanes-tagging (v0.0.5)
+ utilsplugin2 (36011)
+ wikipedia (605)


=== REPORTED CRASH DATA ===
BugReportExceptionHandler#handleException:
No data collected.

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: Timer-0 (99)
java.lang.NullPointerException
	at org.openstreetmap.josm.plugins.continuosDownload.AbstractDownloadStrategy.getExisting(AbstractDownloadStrategy.java:117)
	at org.openstreetmap.josm.plugins.continuosDownload.AbstractDownloadStrategy.fetch(AbstractDownloadStrategy.java:45)
	at org.openstreetmap.josm.plugins.continuosDownload.AbstractDownloadStrategy.fetch(AbstractDownloadStrategy.java:35)
	at org.openstreetmap.josm.plugins.continuosDownload.DownloadPlugin$Task.run(DownloadPlugin.java:221)
	at java.util.TimerThread.mainLoop(Unknown Source)
	at java.util.TimerThread.run(Unknown Source)

[taylor.smock]

This seems really odd -- the NPE location is in MainApplication.getMap().mapView.getLayerManager().getLayers(). We cannot be getting the NPE at MainApplication.getMap() or .mapView -- both of those are checked 4 lines above, with !MainApplication.isDisplayingMapView(), and then 2 lines previous with MainApplication.getMap().mapView.getLayerManager().getEditLayer() (which also means that the null value is not from getLayerManager()).

As such, I'm going to guess that this is a race condition, especially since this occurred in a timer thread. Fixing this might be as easy as moving the actual method calls to the worker thread.

[gaben]

I received the same stack trace again. What I did is a layer deletion just milliseconds before the plugin fired the download tasks.

Cannot reproduce the bug, so I stand with the race condition suspicion as well.

[taylor.smock]

The NPE is (hopefully) fixed in ​83fccdd9b056c5cfed11d4307ae08a055e0d7215.

[gaben]

Thank you!

[taylor.smock]

Like I said, it is hopefully fixed. I'm 90% confident it is, since I got rid of a few NPE possibilities. Please reopen this ticket if it happens again.