End of File exception when opening completion in empty file

[datho7561]

jdt.ls: 0.71.0
VSCode:
1.51.1
e5a624b788d92b8d34d1392e4c4d9789406efe8f
x64

When opening completion at the end of a file with only whitespace, an Exception gets logged:

End Of File
org.eclipse.core.runtime.CoreException: End Of File
	at org.eclipse.jdt.internal.corext.dom.TokenScanner.readNext(TokenScanner.java:153)
	at org.eclipse.jdt.internal.corext.dom.TokenScanner.readNext(TokenScanner.java:191)
	at org.eclipse.jdt.ls.core.internal.contentassist.SnippetCompletionProposal$SnippetCompletionContext.needsPublic(SnippetCompletionProposal.java:116)
	at org.eclipse.jdt.ls.core.internal.contentassist.SnippetCompletionProposal$SnippetCompletionContext.needsPublic(SnippetCompletionProposal.java:97)
	at org.eclipse.jdt.ls.core.internal.contentassist.SnippetCompletionProposal.getClassSnippet(SnippetCompletionProposal.java:336)
	at org.eclipse.jdt.ls.core.internal.contentassist.SnippetCompletionProposal.getTypeDefinitionSnippets(SnippetCompletionProposal.java:273)
	at org.eclipse.jdt.ls.core.internal.contentassist.SnippetCompletionProposal.getSnippets(SnippetCompletionProposal.java:191)
	at org.eclipse.jdt.ls.core.internal.handlers.CompletionHandler.computeContentAssist(CompletionHandler.java:156)
	at org.eclipse.jdt.ls.core.internal.handlers.CompletionHandler.completion(CompletionHandler.java:79)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$4(JDTLanguageServer.java:514)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:75)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:642)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:479)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

I was able to reproduce this in a Maven project and also with a standalone Java file. The snippets appear to work file though.

[rgrunber]

I'm also able to reproduce.

The problem seems to be a mismatch between what TokenScanner does and what JDT-LS expects. JDT-LS wants to read the token, and if ITerminalSymbols.TokenNameEOF is returned , then it will perform some other actions. However, TokenScanner doesn't seem to ever return ITerminalSymbols.TokenNameEOF. If it encounters EOF it simply throws a CoreException with status code TokenScanner.END_OF_FILE .

We can probably just adjust the segment where we catch the CoreException to verify if it is due to EOF and recover accordingly.