Infinite 'Scanning for files to index' due to "UTFDataFormatException: encoded string (^(?:[^/]...ll\);/?$) too long: 618597 bytes" from IgnoreEntryOccurrence

[lj-replicate]

Reported from https://youtrack.jetbrains.com/issue/IJPL-218171.

After loading a huge project, I'm always facing the same problem: an endless loop: "Scanning for files to index". From the log, a exception throws from mobi.hsz.idea.gitignore.indexing.IgnoreEntryOccurrence$Companion.serialize.

After disabling the .ignore plugin, the issue disappears.

2025-11-17 14:35:16,559 [2501588]   INFO - #c.i.u.i.i.MapReduceIndex - An exception during updateWithMap(). Index IgnoreFilesIndex will be rebuilt.
com.intellij.util.indexing.StorageException: Processing of UpdateData[IgnoreFilesIndex: #3602] failed
	at com.intellij.util.indexing.impl.MapReduceIndex.updateWith(MapReduceIndex.java:421)
	at com.intellij.util.indexing.impl.MapReduceIndex$IndexStorageUpdate.update(MapReduceIndex.java:449)
	at com.intellij.util.indexing.FileBasedIndexImpl.lambda$runUpdateForPersistentData$22(FileBasedIndexImpl.java:1745)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeUnderProgress(CoreProgressManager.java:705)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$computeInNonCancelableSection$4(CoreProgressManager.java:298)
	at com.intellij.openapi.progress.Cancellation.computeInNonCancelableSection(Cancellation.java:135)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeInNonCancelableSection(CoreProgressManager.java:298)
	at com.intellij.util.indexing.FileBasedIndexImpl.lambda$runUpdateForPersistentData$23(FileBasedIndexImpl.java:1745)
	at com.intellij.util.indexing.StorageBufferingHandler.runUpdate(StorageBufferingHandler.java:22)
	at com.intellij.util.indexing.FileBasedIndexImpl.runUpdateForPersistentData(FileBasedIndexImpl.java:1743)
	at com.intellij.util.indexing.SingleIndexValueApplier.doApply(SingleIndexValueApplier.java:69)
	at com.intellij.util.indexing.SingleIndexValueApplier.apply(SingleIndexValueApplier.java:57)
	at com.intellij.util.indexing.contentQueue.dev.MultiThreadedWithSuspendIndexWriter.applyModificationsInExecutor(IndexWriter.kt:663)
	at com.intellij.util.indexing.contentQueue.dev.MultiThreadedWithSuspendIndexWriter.writeChangesToIndexes$lambda$5(IndexWriter.kt:643)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$executeNonCancelableSection$3(CoreProgressManager.java:290)
	at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:756)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeUnderProgress(CoreProgressManager.java:712)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$computeInNonCancelableSection$4(CoreProgressManager.java:298)
	at com.intellij.openapi.progress.Cancellation.computeInNonCancelableSection(Cancellation.java:139)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeInNonCancelableSection(CoreProgressManager.java:298)
	at com.intellij.openapi.progress.impl.CoreProgressManager.executeNonCancelableSection(CoreProgressManager.java:289)
	at com.intellij.util.indexing.contentQueue.dev.MultiThreadedWithSuspendIndexWriter.scheduleIndexWriting$lambda$11(IndexWriter.kt:725)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
	at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.io.UTFDataFormatException: encoded string (^(?:[^/]...ll\);/?$) too long: 618597 bytes
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:363)
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:327)
	at mobi.hsz.idea.gitignore.indexing.IgnoreEntryOccurrence$Companion.serialize(IgnoreEntryOccurrence.kt:41)
	at mobi.hsz.idea.gitignore.indexing.IgnoreFilesIndexKt$DATA_EXTERNALIZER$1.save(IgnoreFilesIndex.kt:81)
	at mobi.hsz.idea.gitignore.indexing.IgnoreFilesIndexKt$DATA_EXTERNALIZER$1.save(IgnoreFilesIndex.kt:78)
	at com.intellij.util.indexing.InputMapExternalizer.save(InputMapExternalizer.java:79)
	at com.intellij.util.indexing.InputMapExternalizer.save(InputMapExternalizer.java:26)
	at com.intellij.util.indexing.impl.forward.AbstractForwardIndexAccessor.serializeToByteSeq(AbstractForwardIndexAccessor.java:113)
	at com.intellij.util.indexing.impl.forward.AbstractForwardIndexAccessor.serializeValueToByteSeq(AbstractForwardIndexAccessor.java:99)
	at com.intellij.util.indexing.impl.forward.AbstractForwardIndexAccessor.serializeIndexedData(AbstractForwardIndexAccessor.java:50)
	at com.intellij.util.indexing.impl.forward.AbstractForwardIndexAccessor.serializeIndexedData(AbstractForwardIndexAccessor.java:75)
	at com.intellij.util.indexing.impl.MapReduceIndex.updateForwardIndex(MapReduceIndex.java:331)
	at com.intellij.util.indexing.impl.storage.TransientFileContentIndex.updateForwardIndex(TransientFileContentIndex.java:85)
	at com.intellij.util.indexing.impl.MapReduceIndex.lambda$prepareUpdate$4(MapReduceIndex.java:308)
	at com.intellij.util.indexing.impl.UpdateData.updateForwardIndex(UpdateData.java:55)
	at com.intellij.util.indexing.impl.MapReduceIndex.updateWith(MapReduceIndex.java:413)
	... 24 more
2025-11-17 14:35:16,563 [2501592]   WARN - #c.i.u.i.FileBasedIndexImpl - Suppressed a frequent exception logged for the 2nd time: Processing of UpdateData[IgnoreFilesIndex: #3602] failed