fix: Handle Diagnostic with null severity

[FlorianKroiss]

Handle case null for Diagnostic::severity. We encountered several NPEs due to this:

ERROR 2026-01-13 16:28:43.442 [Text Viewer Hover Presenter] org.eclipse.equinox.logger - Unexpected runtime error while computing a text hover
java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.DiagnosticSeverity.ordinal()" because the return value of "org.eclipse.lsp4j.Diagnostic.getSeverity()" is null
	at org.eclipse.lsp4e.operations.diagnostics.DiagnosticAnnotation.getType(DiagnosticAnnotation.java:32)
	at org.eclipse.ui.texteditor.AnnotationPreferenceLookup.getAnnotationPreference(AnnotationPreferenceLookup.java:51)
	at org.eclipse.ui.internal.genericeditor.AnnotationHoverDelegate$1.isIncluded(AnnotationHoverDelegate.java:44)
	at org.eclipse.jface.text.DefaultTextHover.getHoverInfo(DefaultTextHover.java:60)
	at org.eclipse.ui.internal.genericeditor.AnnotationHoverDelegate.getHoverInfo(AnnotationHoverDelegate.java:68)
	at org.eclipse.ui.internal.genericeditor.hover.CompositeTextHover.getHoverInfo2(CompositeTextHover.java:60)
	at org.eclipse.jface.text.TextViewerHoverManager$1.run(TextViewerHoverManager.java:155)

and

java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.DiagnosticSeverity.ordinal()" because the return value of "org.eclipse.lsp4j.Diagnostic.getSeverity()" is null
	at org.eclipse.lsp4e.operations.diagnostics.DiagnosticAnnotation.getType(DiagnosticAnnotation.java:32)
	at org.eclipse.jface.text.source.OverviewRuler$InternalListener.modelChanged(OverviewRuler.java:108)
	at org.eclipse.jface.text.source.AnnotationModel.fireModelChanged(AnnotationModel.java:592)
	at org.eclipse.jface.text.source.AnnotationModel$InternalModelListener.modelChanged(AnnotationModel.java:256)
	at org.eclipse.jface.text.source.AnnotationModel.fireModelChanged(AnnotationModel.java:592)
	at org.eclipse.jface.text.source.AnnotationModel.fireModelChanged(AnnotationModel.java:558)
	at org.eclipse.jface.text.source.AnnotationModel.replaceAnnotations(AnnotationModel.java:409)
	at org.eclipse.jface.text.source.AnnotationModel.replaceAnnotations(AnnotationModel.java:374)
	at org.eclipse.lsp4e.operations.diagnostics.LSPDiagnosticsToMarkers.updateEditorAnnotations(LSPDiagnosticsToMarkers.java:137)
	at org.eclipse.lsp4e.operations.diagnostics.LSPDiagnosticsToMarkers.accept(LSPDiagnosticsToMarkers.java:102)
	at org.eclipse.lsp4e.operations.diagnostics.LSPDiagnosticsToMarkers.accept(LSPDiagnosticsToMarkers.java:1)
	at org.eclipse.lsp4e.client.DefaultLanguageClient.publishDiagnostics(DefaultLanguageClient.java:110)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$recursiveFindRpcMethods$0(GenericEndpoint.java:65)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.notify(GenericEndpoint.java:160)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleNotification(RemoteEndpoint.java:231)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:198)
	at org.eclipse.lsp4e.LanguageServerWrapper.lambda$3(LanguageServerWrapper.java:449)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:185)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:97)
	at org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:114)
	at java.base/java.util.concurrent.Executors$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)

[FlorianKroiss]

I redirected the case for null to super.getType() which should always return org.eclipse.text.annotation.unknown. I just had another look at the LSP Spec, which actually says that an absent severity should be treated as error severity. Should we use that instead?

[rubenporras]

I redirected the case for null to super.getType() which should always return org.eclipse.text.annotation.unknown. I just had another look at the LSP Spec, which actually says that an absent severity should be treated as error severity. Should we use that instead?

Yes, I would follow the spec.

[rubenporras]

let us follow the spec and use error.