Xtext LSP vscode integration exception thrown on content assist

[srinivasiyermv]

Hello all,

I am trying to integrate a simple DSL based on xtext with vscode .. I followed the demo application .. While integrating into my sample everything works apart from content assist. We get below error . Any idea what needs to be fixed here

Using the latest lsp4j and language client as described in demo .

47734688 [pool-1-thread-5] ERROR t.antlr.ContentAssistContextFactory  - java.lang.RuntimeException: java.lang.NullPointerException
java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.NullPointerException
	at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.ContentAssistContextFactory.doCreateContexts(ContentAssistContextFactory.java:181)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.ContentAssistContextFactory.create(ContentAssistContextFactory.java:131)
	at org.eclipse.xtext.ide.server.contentassist.ContentAssistService.createProposals(ContentAssistService.java:106)
	at org.eclipse.xtext.ide.server.contentassist.ContentAssistService.createCompletionList(ContentAssistService.java:78)
	at org.eclipse.xtext.ide.server.LanguageServerImpl.lambda$26(LanguageServerImpl.java:587)
	at org.eclipse.xtext.ide.server.WorkspaceManager.doRead(WorkspaceManager.java:458)
	at org.eclipse.xtext.ide.server.LanguageServerImpl.completion(LanguageServerImpl.java:586)
	at org.eclipse.xtext.ide.server.LanguageServerImpl.lambda$25(LanguageServerImpl.java:572)
	at org.eclipse.xtext.ide.server.concurrent.ReadRequest.lambda$1(ReadRequest.java:66)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
	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.lang.RuntimeException: java.lang.NullPointerException
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:246)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:237)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:232)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.AbstractContentAssistParser.getFollowElements(AbstractContentAssistParser.java:49)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.AbstractContentAssistParser.getFollowElements(AbstractContentAssistParser.java:1)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:264)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.ContentAssistContextFactory.handleLastCompleteNodeIsAtEndOfDatatypeNode(ContentAssistContextFactory.java:230)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.ContentAssistContextFactory$2.call(ContentAssistContextFactory.java:161)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.ContentAssistContextFactory$2.call(ContentAssistContextFactory.java:1)
	... 4 more
Caused by: java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:233)
	at java.base/java.lang.Class.getMethod(Class.java:2387)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:169)
	at org.eclipse.xtext.ide.editor.contentassist.antlr.BaseContentAssistParser.getFollowElements(BaseContentAssistParser.java:242)
	... 12 more

[cdietrich]

hi, i propose you debug what is null. why is the method not found?
also: do you have a reproducer?
maybe you are doing something unexpected in grammar.

[srinivasiyermv]

Thanks Christian for quick response .. I dont have reproducer . However debugging found out that rule object id are different which is causing null

org.eclipse.xtext.xtext.RuleNames

public String getAntlrRuleName(AbstractRule rule) {
		return antlrNameToRule.inverse().get(rule);
	}

Object id are different as compared to the antlrNameToRule.inverse() however the rule names are present . Looks like the parse which we inject from IDE is different .. Correct me is this right understanding .Thanks

[cdietrich]

yes but the question is why.
do you have customized any bindings?
do you have multiple file extension?

[srinivasiyermv]

We have custom Class<? extends IdeContentProposalProvider> bindIdeContentProposalProvider() this is only customized bindings which is added in ide .

We dont have multiple file extension

[cdietrich]

and what did you customize?

[cdietrich]

i really need a reproducer

[srinivasiyermv]

Thanks Christian .. Will try to create a reproducer and check if its reproducible with similar scenario and get back to you. May be you could close this issue as its more relevant for our use case. Thanks again