NPE while loading a save-file

[Dirk-c-Walter]

Environment

Linux Megamek 0.49.10, java 11.0.13

Description

Loading a save game fails. After some digging through the logs and the error message it seems to be unhappy about some Arrow IV attacks made by infantry.

Files

night.sav.gz

Log message bellow;
19:35:13,427 INFO [megamek.MegaMek] {main}
megamek.MegaMek.initializeLogging(MegaMek.java:115) - Starting MegaMek v0.49.10
Build Date: N/A
Today: 2022-12-04
Origin Project: MegaMek
Java Vendor: Ubuntu
Java Version: 11.0.13
Platform: Linux 5.11.0-49-generic (amd64)
System Locale: en_US
Total memory available to MegaMek: 2 GB

19:35:13,429 INFO [megamek.MegaMek] {main}
megamek.MegaMek.handleLegacyLogging(MegaMek.java:128) - Redirecting System.out, System.err, and Throwable::printStackTrace output to legacy.log

19:35:13,546 INFO [megamek.client.ui.preferences.SuitePreferences] {main}
megamek.client.ui.preferences.SuitePreferences.loadFromFile(SuitePreferences.java:118) - Loading user preferences from: mmconf/mm.preferences

19:35:13,583 INFO [megamek.client.ui.preferences.SuitePreferences] {main}
megamek.client.ui.preferences.SuitePreferences.loadFromFile(SuitePreferences.java:138) - Finished loading user preferences

19:35:13,815 INFO [megamek.MegaMek] {main}
megamek.MegaMek.startGUI(MegaMek.java:315) - Starting MegaMekGUI.

19:35:21,528 ERROR [megamek.client.ui.swing.MegaMekGUI] {AWT-EventQueue-0}
megamek.client.ui.swing.MegaMekGUI.loadGame(MegaMekGUI.java:548) - Unable to load file: /home/dirk/apps/mekhq-0.49.10/savegames/night.sav.gz
com.thoughtworks.xstream.converters.ConversionException: Failed calling method
---- Debugging information ----
message : Failed calling method
cause-exception : java.lang.NullPointerException
cause-message : null
method : megamek.common.weapons.ArtilleryWeaponIndirectFireHandler.readObject()
class : megamek.common.weapons.ArtilleryWeaponIndirectFireHandler
required-type : megamek.common.weapons.ArtilleryWeaponIndirectFireHandler
converter-type : com.thoughtworks.xstream.converters.reflection.SerializableConverter
line number : 545411
class[1] : java.util.Vector
required-type[1] : java.util.Vector
converter-type[1] : com.thoughtworks.xstream.converters.collections.CollectionConverter
class[2] : megamek.common.Game
required-type[2] : megamek.common.Game
converter-type[2] : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version : 1.4.14

at com.thoughtworks.xstream.core.util.SerializationMembers.callReadObject(SerializationMembers.java:136)
at com.thoughtworks.xstream.converters.reflection.SerializableConverter.doUnmarshal(SerializableConverter.java:443)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:277)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readBareItem(AbstractCollectionConverter.java:132)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:117)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.addCurrentElementToCollection(CollectionConverter.java:98)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:91)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:85)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.unmarshal(CollectionConverter.java:80)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshallField(AbstractReflectionConverter.java:499)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:425)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:277)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1404)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1383)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1277)
at megamek.client.ui.swing.MegaMekGUI.loadGame(MegaMekGUI.java:546)
at megamek.client.ui.swing.MegaMekGUI.lambda$new$0(MegaMekGUI.java:935)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$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.Component.processMouseEvent(Component.java:6635)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at megamek.client.ui.swing.widget.MegamekButton.processMouseEvent(MegamekButton.java:242)
at java.desktop/java.awt.Component.processEvent(Component.java:6400)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5011)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4843)
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:4843)
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)

Caused by: java.lang.NullPointerException
at megamek.common.weapons.WeaponHandler.readObject(WeaponHandler.java:435)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at com.thoughtworks.xstream.core.util.SerializationMembers.callReadObject(SerializationMembers.java:132)
... 65 more

[Windchild292]

Can you please post the full log files (legacy, MM, and, if related, MHQ) from loading this file? This appears to be a critical bug at first read.

[Dirk-c-Walter]

I've tracked down the issue, it;s a race condition during loadign the save.

megamek/megamek/src/megamek/common/weapons/WeaponHandler.java

Line 435 in 81231b4

gameManager = (GameManager) Server.getServerInstance().getGameManager();

The Server Instance is still null when that is being accsessed, However after several tries I was able to get it to load.

[Dirk-c-Walter]

If you still need the logs I can post them, but I'll see if I can write a patch for this over christmas vacation.

[Windchild292]

The error message in question normally originates from different game versions, which is why I wanted the log to check. However, I've found a location where this state of affairs can occur, namely

megamek/megamek/src/megamek/client/ui/swing/MegaMekGUI.java

Lines 543 to 552 in 7772631

	Game newGame;
	try (InputStream is = new FileInputStream(fc.getSelectedFile()); InputStream gzi = new GZIPInputStream(is)) {
	XStream xstream = SerializationHelper.getXStream();
	newGame = (Game) xstream.fromXML(gzi);
	} catch (Exception e) {
	LogManager.getLogger().error("Unable to load file: " + fc.getSelectedFile().getAbsolutePath(), e);
	JOptionPane.showMessageDialog(frame, Messages.getFormattedString("MegaMek.LoadGameAlert.message", fc.getSelectedFile().getAbsolutePath()),
	Messages.getString("MegaMek.LoadGameAlert.title"), JOptionPane.ERROR_MESSAGE);
	return;
	}

This was added in #2458, and started showing as an issue with #3652.