Do not call FindReferencesAsync for null symbol

[filipw]

At the moment, on finding references, when the requested symbol is null, we still call Roslyn reference finder API which then results in an ugly unhandled exception.

System.InvalidOperationException: Unexpected null\r\n at Roslyn.Utilities.Contract.Fail(String message)\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.MapToAppropriateSymbol(ISymbol symbol)\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.d__20.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.d__19.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.CodeAnalysis.FindSymbols.SymbolFinder.d__34.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.CodeAnalysis.FindSymbols.SymbolFinder.d__37.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at OmniSharp.Roslyn.CSharp.Services.Navigation.FindUsagesService.d__2.MoveNext() in D:\\a\\1\\s\\src\\OmniSharp.Roslyn.CSharp\\Services\\Navigation\\FindUsagesService.cs:line 41

This happens automatically when the member is invalid and in VS Code shows up in a horrible way:

This also happens when you click anywhere in the code on a non-symbol e.g. the "public" keyword and try to use "find references"

Fixes dotnet/vscode-csharp#4382
Fixes #2054

[VincentDondain]

Hey @filipw, how do I know if this has been released? I'm using the C# extension v1.23.9 and I still see that issue.

[filipw]

it was not integrated into the C# extension yet