NPE in XMLTextDocumentService.computeDOMAsync

[apupier]

spotted in log:

Jan 07, 2021 1:55:18 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint fallbackResponseError
SEVERE: Internal error: java.lang.reflect.InvocationTargetException
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$null$0(GenericEndpoint.java:67)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.request(GenericEndpoint.java:120)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleRequest(RemoteEndpoint.java:261)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:190)
	at org.eclipse.lemminx.commons.ParentProcessWatcher.lambda$apply$0(ParentProcessWatcher.java:143)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:194)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:94)
	at org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:113)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.reflect.InvocationTargetException
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$null$0(GenericEndpoint.java:65)
	... 12 more
Caused by: java.lang.NullPointerException
	at org.eclipse.lemminx.XMLTextDocumentService.computeDOMAsync(XMLTextDocumentService.java:546)
	at org.eclipse.lemminx.XMLTextDocumentService.foldingRange(XMLTextDocumentService.java:316)
	... 17 more

I do not have steps to reproduce.
I'm using org.eclipse.wildwebdeveloper.xml 0.9.1.202007231627

[angelozerr]

Indeed I noticed this problem, but it occurs only in WWD (not in vscode).

To reproduce the problem it's easy, you open a XML file and you should see this error (sometimes).

The main reason is that LSP foldingRange request is called BEFORE the LSP didOpen. LSP4E folding reconcilier is processed before the didOpen //cc @mickaelistria .

We should take care of this NPE like other language server like JSON in vscode https://github.com/vscode-langservers/vscode-json-languageserver/blob/a24ff2be8707c1a9c82a699db1033de6c7215f45/src/jsonServer.ts#L464