Lucene errors after update to 4.31

[gvl2023]

Getting the following error after updating to the 4.31 simultaneous release. Happens on startup and task list synchronization. More of a nuisance as it doesn't appear to affect basic functionalities. Any workarounds?

An internal error occurred during: "Task List Indexer".

java.lang.IllegalArgumentException: Could not load codec 'Lucene95'. Did you forget to add lucene-backward-codecs.jar?
	at org.apache.lucene.index.SegmentInfos.readCodec(SegmentInfos.java:520)
	at org.apache.lucene.index.SegmentInfos.parseSegmentInfos(SegmentInfos.java:409)
	at org.apache.lucene.index.SegmentInfos.readCommit(SegmentInfos.java:368)
	at org.apache.lucene.index.SegmentInfos.readCommit(SegmentInfos.java:304)
	at org.apache.lucene.index.SegmentInfos$1.doBody(SegmentInfos.java:546)
	at org.apache.lucene.index.SegmentInfos$1.doBody(SegmentInfos.java:543)
	at org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:820)
	at org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:770)
	at org.apache.lucene.index.SegmentInfos.readLatestCommit(SegmentInfos.java:548)
	at org.apache.lucene.index.SegmentInfos.readLatestCommit(SegmentInfos.java:532)
	at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:1011)
	at org.eclipse.mylyn.internal.tasks.index.core.TaskListIndex.createIndexWriter(TaskListIndex.java:1282)
	at org.eclipse.mylyn.internal.tasks.index.core.TaskListIndex.rebuildIndexCompletely(TaskListIndex.java:1228)
	at org.eclipse.mylyn.internal.tasks.index.core.TaskListIndex.maintainIndex(TaskListIndex.java:1095)
	at org.eclipse.mylyn.internal.tasks.index.core.TaskListIndex$MaintainIndexJob.run(TaskListIndex.java:184)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
	Suppressed: org.apache.lucene.index.CorruptIndexException: checksum passed (9cd13f06). possibly transient resource issue, or a Lucene or JVM bug (resource=BufferedChecksumIndexInput(NIOFSIndexInput(path="/home/vladg/workspace/eclipse-workspace/.metadata/.mylyn/.taskListIndex/segments_1a")))
		at org.apache.lucene.codecs.CodecUtil.checkFooter(CodecUtil.java:501)
		at org.apache.lucene.index.SegmentInfos.readCommit(SegmentInfos.java:375)
		... 13 more
Caused by: java.lang.IllegalArgumentException: An SPI class of type org.apache.lucene.codecs.Codec with name 'Lucene95' does not exist.  You need to add the corresponding JAR file supporting this SPI to your classpath.  The current classpath supports the following names: [Lucene99]
	at org.apache.lucene.util.NamedSPILoader.lookup(NamedSPILoader.java:113)
	at org.apache.lucene.codecs.Codec.forName(Codec.java:118)
	at org.apache.lucene.index.SegmentInfos.readCodec(SegmentInfos.java:516)
	... 15 more

[gvl2023]

Solved this by deleting all files in eclipse-workspace/.metadata/.mylyn/.taskListIndex and restarting Eclipse. Looks like Mylyn can't gracefully handle Lucene version upgrade between Eclipse releases. Perhaps the Refresh Search Index operation should verify that index is valid with respect to available lucene versions and rebuild from scratch as needed.

[ruspl-afed]

Thanks you for the suggested workaround @gvl2023 I added codecs just before the release but had no chance to verify the fix.

[mjmeijer]

See #464