[Language server] The C# Language server does not validate a code properly in certain cases

[musienko-maxim]

Description

Steps to reproduce:

• Create a workspace based on .Net stack.
• Open the workspace and create dotnet-web-simple project from wizard
• Open Program.cs file and wait language server initialization.

Expected result: The code validation should start. We should see inform markers.
Actual result: There are no markers.

Failed test: CSharpFileEditingTest

Additional information
If we delete for example symbol ; from .Build(); fragment, the codevalidation works properly.
But if we do some mistake in the code - we will get exception in the dev. console like:

at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292)
at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647)
at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265)
at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)java.util.concurrent.CompletionException: java.util.concurrent.CancellationException	
at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308)	
at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116)

After that the main LS features (codevalidation, codecompletion, etc.) do not work.

Hover feature

Steps to reproduce:

• Create a workspace based on .Net stack.
• Open the workspace and create dotnet-web-simple project from wizard.
• Open Program.cs file and wait language server initialization.
• Reopen Program.cs file(for now it need because of issue with language server install dependencies). Inform markers should be visible.
• Move mouse pointer to WebHost.CreateDefaultBuilder(args) code in line 21 and wait to hover popup.
• Move mouse pointer from this line and return.

Expected result: Hover popup is visible again.

Actual result: There are exceptions in the "dev-machine" console(see logs below) and the main LS features (codevalidation, codecompletion, etc.) do not work.

2018-09-14 08:08:10,748[equestProcessor]  [INFO ] [o.e.c.a.l.util.OperationUtil 91]     - Exception occurred in request
java.util.concurrent.CompletionException: java.util.concurrent.CancellationException
	at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292)
	at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308)
	at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647)
	at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632)
	at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
	at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116)
	at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115)
	at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390)
	at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76)
	at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351)
	at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335)
	at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224)
	at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265)
	at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308)
	at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52)
	at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98)
	at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73)
	at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.util.concurrent.CancellationException: null
	at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263)
	... 14 common frames omitted

Additional information

Screencast:

Screenshots:

dev-machine console logs

``` java 2018-09-14 08:08:10,748[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.util.concurrent.CancellationException: null at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) ... 14 common frames omitted Caused by: java.util.concurrent.CancellationException: null 2018-09-14 08:08:12,052[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ... 14 common frames omitted at java.lang.Thread.run(Thread.java:748) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) 2018-09-14 08:08:12,059[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request Caused by: java.util.concurrent.CancellationException: null java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.lang.Thread.run(Thread.java:748) Caused by: java.util.concurrent.CancellationException: null at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) ... 14 common frames omitted 2018-09-14 08:08:12,072[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.util.concurrent.CancellationException: null at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) ... 14 common frames omitted java.util.concurrent.CompletionException: java.util.concurrent.CancellationException 2018-09-14 08:08:12,074[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.util.concurrent.CancellationException: null ... 14 common frames omitted 2018-09-14 08:08:12,075[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) ... 14 common frames omitted at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) Caused by: java.util.concurrent.CancellationException: null at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) 2018-09-14 08:08:12,083[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at java.lang.Thread.run(Thread.java:748) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) Caused by: java.util.concurrent.CancellationException: null at java.lang.Thread.run(Thread.java:748) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) ... 14 common frames omitted at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) ... 14 common frames omitted 2018-09-14 08:08:12,485[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at java.lang.Thread.run(Thread.java:748) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) Caused by: java.util.concurrent.CancellationException: null 2018-09-14 08:08:12,494[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at java.lang.Thread.run(Thread.java:748) Caused by: java.util.concurrent.CancellationException: null ... 14 common frames omitted at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) Caused by: java.util.concurrent.CancellationException: null java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at java.lang.Thread.run(Thread.java:748) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) 2018-09-14 08:08:12,510[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) 2018-09-14 08:08:12,505[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) ... 14 common frames omitted at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.commons.lang.concurrent.CopyThreadLocalRunnable.run(CopyThreadLocalRunnable.java:38) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) ... 14 common frames omitted java.util.concurrent.CompletionException: java.util.concurrent.CancellationException at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.processRequest(JsonRpcMessageReceiver.java:98) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) 2018-09-14 08:08:12,519[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) Caused by: java.util.concurrent.CancellationException: null at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:647) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) Caused by: java.util.concurrent.CancellationException: null 2018-09-14 08:08:12,523[equestProcessor] [INFO ] [o.e.c.a.l.util.OperationUtil 91] - Exception occurred in request ... 14 common frames omitted at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at java.lang.Thread.run(Thread.java:748) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.reception.FunctionConfiguratorOneToOne.lambda$withFunction$0(FunctionConfiguratorOneToOne.java:76) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292) at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) at java.lang.Thread.run(Thread.java:748) at org.eclipse.che.api.languageserver.util.OperationUtil.doInParallel(OperationUtil.java:115) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager.handle(RequestHandlerManager.java:224) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.core.jsonrpc.commons.JsonRpcMessageReceiver.lambda$receive$0(JsonRpcMessageReceiver.java:73) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2265) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint$1.cancel(RemoteEndpoint.java:116) at org.eclipse.che.api.core.jsonrpc.commons.RequestDispatcher.dispatch(RequestDispatcher.java:52) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.access$1000(RequestHandlerManager.java:335) at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308) at java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2263) at org.eclipse.che.api.core.jsonrpc.commons.RequestHandlerManager$OneToOneHandler.handle(RequestHandlerManager.java:351) at org.eclipse.che.api.languageserver.TextDocumentService.hover(TextDocumentService.java:390) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ```

[musienko-maxim]

After fixing we should remove try/catch block from CSharpFileEditingTest

[SkorikSergey]

It looks like that main reason is opening Program.cs file before language server is fully initialized. When we are trying to open this file we have 30 sec for the language server to initialize and after that file will be opened in the Editor. But, mostly, this timeout is too short for initializing and the file will be opened in the Editor when the language server not started yet. So the language server will not work with opened file until this file reopening.

[SkorikSergey]

Not relevant anymore. Closing.