[PATCH] junctionchecking may try to add itself two or more times to the activelayerchangelisteners

[taylor.smock]

What steps will reproduce the problem?

1. Start JOSM
2. Download/Open an area (see the attached file for what I was looking at if not reproducible otherwise)
3. Create the ChannelDiGraphLayer
4. Delete the ChannelDiGraphLayer
5. Crash occurs

What is the expected result?

No crash

What happens instead?

Crash

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

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-03-03 00:16:03 +0100 (Sun, 03 Mar 2019)
Revision:14824
Build-Date:2019-03-02 23:16:53
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (14824 en) Mac OS X 10.14.4
OS Build number: Mac OS X 10.14.4 (18E226)
Memory Usage: 368 MB / 2048 MB (143 MB allocated, but free)
Java version: 11.0.1+13, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: Display 188945226 1920x1080, Display 69978068 2048x1152
Maximum Screen Size: 2048x1152
VM arguments: [-Djosm.pref=./tmp]
Dataset consistency test: No problems found

Plugins:
+ junctionchecking (34678)

Last errors/warnings:
- E: java.io.IOException: java.util.concurrent.ExecutionException: [security, find-certificate, -c, Government Root Certification Authority, -p, /System/Library/Keychains/SystemRootCertificates.keychain]. Cause: java.util.concurrent.ExecutionException: [security, find-certificate, -c, Government Root Certification Authority, -p, /System/Library/Keychains/SystemRootCertificates.keychain]
- W: Update plugins - org.openstreetmap.josm.plugins.PluginHandler$UpdatePluginsMessagePanel[,0,0,0x0,invalid,layout=java.awt.GridBagLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=]
- W: No configuration settings found.  Using hardcoded default values for all pools.
- E: Thread main-worker-0 raised ReportedException [thread=Thread[main-worker-0,5,main], exception=java.lang.reflect.InvocationTargetException, methodWarningFrom=null]
- E: Handled by bug report queue: java.lang.IllegalArgumentException: Attempted to add listener that was already in list: org.openstreetmap.josm.plugins.JunctionChecker.JunctionCheckerMapMode@400f8d4d


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (19) of main
java.lang.IllegalArgumentException: Attempted to add listener that was already in list: org.openstreetmap.josm.plugins.JunctionChecker.JunctionCheckerMapMode@400f8d4d
	at org.openstreetmap.josm.gui.layer.MainLayerManager.addActiveLayerChangeListener(MainLayerManager.java:177)
	at org.openstreetmap.josm.plugins.JunctionChecker.JunctionCheckerMapMode.enterMode(JunctionCheckerMapMode.java:44)
	at org.openstreetmap.josm.gui.MapFrame.activeOrEditLayerChanged(MapFrame.java:846)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.fireActiveLayerChange(MainLayerManager.java:271)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.setActiveLayer(MainLayerManager.java:264)
	at org.openstreetmap.josm.gui.layer.MainLayerManager.realRemoveSingleLayer(MainLayerManager.java:304)
	at org.openstreetmap.josm.gui.layer.LayerManager.realRemoveLayer(LayerManager.java:266)
	at org.openstreetmap.josm.gui.layer.LayerManager.lambda$removeLayer$1(LayerManager.java:248)
	at org.openstreetmap.josm.gui.util.GuiHelper.runInEDTAndWaitWithException(GuiHelper.java:238)
	at org.openstreetmap.josm.gui.layer.LayerManager.removeLayer(LayerManager.java:248)
	at org.openstreetmap.josm.gui.dialogs.layer.DeleteLayerAction.actionPerformed(DeleteLayerAction.java:52)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
	at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
	at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297)
	at java.desktop/java.awt.Component.processMouseEvent(Component.java:6632)
	at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
	at java.desktop/java.awt.Component.processEvent(Component.java:6397)
	at java.desktop/java.awt.Container.processEvent(Container.java:2263)
	at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5008)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
	at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
	at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
	at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
	at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

[taylor.smock]

Possible fix for crash

[taylor.smock]

Example data area

[Don-vip]

I would prefer a proper patch that addresses the root cause.

[Don-vip]

Ticket #16670 has been marked as a duplicate of this ticket.

[taylor.smock]

Actually fix the issue (remove listener when leaving the layer -- this may not be what the original author intended).

[Don-vip]

Fixed in [o34951:34952].