Fixing override completion in VSCode when LSP is enabled (#12039)

* Fixing override completion in VSCode when LSP is enbaled

Existing code worked for the most part. The main issue was that parameters for the complex edit command come in as JsonElements in this case and need to be deserialized.

* CR suggestion - simplify logic

Author: alexgav

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Completion/Delegation/DelegatedCompletionHelper.cs

@@ -6,6 +6,7 @@
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
+using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
@@ -317,6 +318,14 @@ public static async Task<VSInternalCompletionItem> FormatCSharpCompletionItemAsy
         // rather than the one LSP knows about.
         if (resolvedCompletionItem.Command is { CommandIdentifier: Constants.CompleteComplexEditCommand, Arguments: var args })
         {
+            // In LSP case, command parameters will be JsonElement objects and will need to be deserialized first
+            if (args is [JsonElement textDocumentIdentifierData, JsonElement complexEditData, _, _])
+            {
+                args[0] = textDocumentIdentifierData.Deserialize<TextDocumentIdentifier>() ?? args[0];
+                args[1] = complexEditData.Deserialize<TextEdit>() ?? args[1];
+            }
+
+            // In cohosting case, command parameters will be of the correct types (or deserialized by now in LSP case)
             if (args is [TextDocumentIdentifier, TextEdit complexEdit, _, int nextCursorPosition])
             {
                 var formattedTextEdit = await FormatTextEditsAsync([complexEdit], documentContext, options, formattingService, cancellationToken).ConfigureAwait(false);