NullPointerException when using WorkspaceFolders in LSP initialization request

[jnt0r]

As soon as I set the WorkspaceFolders Property in the LSP initialization request, I get a NullPointerException in the xtext LSP server.
I tried different values for the property in different formats, but I always get the same exception.

java.util.concurrent.CompletionException: java.lang.NullPointerException
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:331)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:346)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:632)
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
	at java.base/java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:2088)
	at org.eclipse.xtext.ide.server.concurrent.AbstractRequest.logAndCompleteExceptionally(AbstractRequest.java:73)
	at org.eclipse.xtext.ide.server.concurrent.WriteRequest.run(WriteRequest.java:55)
	at java.base/java.util.concurrent.Executors$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:829)

Caused by: java.lang.NullPointerException
	at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
	at java.base/java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
	at org.eclipse.xtext.resource.impl.ChunkedResourceDescriptions.setContainer(ChunkedResourceDescriptions.java:92)
	at org.eclipse.xtext.ide.server.ProjectManager.createNewResourceSet(ProjectManager.java:145)
	at org.eclipse.xtext.ide.server.ProjectManager.createFreshResourceSet(ProjectManager.java:155)
	at org.eclipse.xtext.ide.server.ProjectManager.newBuildRequest(ProjectManager.java:124)
	at org.eclipse.xtext.ide.server.ProjectManager.doBuild(ProjectManager.java:106)
	at org.eclipse.xtext.ide.server.ProjectManager.doInitialBuild(ProjectManager.java:98)
	at org.eclipse.xtext.ide.server.BuildManager.doInitialBuild(BuildManager.java:164)
	at org.eclipse.xtext.ide.server.WorkspaceManager.refreshWorkspaceConfig(WorkspaceManager.java:254)
	at org.eclipse.xtext.ide.server.WorkspaceManager.initialize(WorkspaceManager.java:173)
	at org.eclipse.xtext.ide.server.LanguageServerImpl.lambda$0(LanguageServerImpl.java:239)
	at org.eclipse.xtext.ide.server.concurrent.WriteRequest.run(WriteRequest.java:50)
	... 5 more

[cdietrich]

Can you provide a reproducer unit test

[jnt0r]

I try to. I don't have a working xtext workspace yet and have to set it up first.
I tested it with the simple greetings starter DSL and the ballerina/lsp4intellij Plugin (newest version from master).

[cdietrich]

you should be able to create a test in a new mydsl project
alternatively you can try to debug the server and find out why it creates project with no names e.g.
MultiRootWorkspaceConfigFactory

[jnt0r]

I created a sample project https://github.com/jnt0r/xtext-npe-reproducable
Test is located here https://github.com/jnt0r/xtext-npe-reproducable/blob/master/org.xtext.example.mydsl.tests/src/org/xtext/example/mydsl/tests/MyLSPWorkspaceFoldersTest.java

I created multiple tests and figured out that it seems to depend on the name of the WorkspaceFolder.
Is this field really required? Wouldn't it be more convenient to throw dedicated errors instead of a NullPointerException?
I read that the WorkspaceFolder name defaults to the name of the specified folder in the provided uri.

[cdietrich]

Xtext try’s to provide a project name from a folder name and currently we at lease need some name
I don’t know why we don’t throw a dedicated error. Needs to be looked at

[cdietrich]

Reading
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspaceFolder
I don’t see the name to be optional

[jnt0r]

I got the optional thing from the LSP4J documentation: https://www.javadoc.io/static/org.eclipse.lsp4j/org.eclipse.lsp4j/0.21.0/org/eclipse/lsp4j/WorkspaceFolder.html
I will also address this at the lsp4intellij project to also send the name, as it is not optional in the LSP specification.

[cdietrich]

maybe should be fixed in lsp4j

[cdietrich]

created eclipse-lsp4j/lsp4j#741

[jnt0r]

eclipse-lsp4j/lsp4j#741 has been fixed and closed.