Deduplicate code to generate the symbol display string for navigation

src/EditorFeatures/Core/Extensibility/Navigation/NavigableItemFactory.DeclaredSymbolNavigableItem.cs

@@ -44,20 +44,7 @@ public DeclaredSymbolNavigableItem(Document document, DeclaredSymbolInfo declare
                             return null;
                         }
 
-                        var symbolDisplayService = Document.GetLanguageService<ISymbolDisplayService>();
-                        switch (Symbol.Kind)
-                        {
-                            case SymbolKind.NamedType:
-                                return symbolDisplayService.ToDisplayString(Symbol, s_shortFormatWithModifiers);
-
-                            case SymbolKind.Method:
-                                return Symbol.IsStaticConstructor()
-                                    ? symbolDisplayService.ToDisplayString(Symbol, s_shortFormatWithModifiers)
-                                    : symbolDisplayService.ToDisplayString(Symbol, s_shortFormat);
-
-                            default:
-                                return symbolDisplayService.ToDisplayString(Symbol, s_shortFormat);
-                        }
+                        return GetSymbolDisplayString(Document.Project, Symbol);
                     }
                     catch (Exception e) when (FatalError.Report(e))
                     {

src/EditorFeatures/Core/Extensibility/Navigation/NavigableItemFactory.SymbolLocationNavigableItem.cs

@@ -28,21 +28,7 @@ private class SymbolLocationNavigableItem : INavigableItem
 
                 _lazyDisplayName = new Lazy<string>(() =>
                 {
-                    var symbolDisplayService = this.Document.Project.LanguageServices.GetService<ISymbolDisplayService>();
-
-                    switch (symbol.Kind)
-                    {
-                        case SymbolKind.NamedType:
-                            return symbolDisplayService.ToDisplayString(_symbol, s_shortFormatWithModifiers);
-
-                        case SymbolKind.Method:
-                            return _symbol.IsStaticConstructor()
-                                ? symbolDisplayService.ToDisplayString(_symbol, s_shortFormatWithModifiers)
-                                : symbolDisplayService.ToDisplayString(_symbol, s_shortFormat);
-
-                        default:
-                            return symbolDisplayService.ToDisplayString(_symbol, s_shortFormat);
-                    }
+                    return GetSymbolDisplayString(Document.Project, _symbol);
                 });
             }
 

src/EditorFeatures/Core/Extensibility/Navigation/NavigableItemFactory.cs

@@ -2,8 +2,10 @@
 
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using Microsoft.CodeAnalysis.FindSymbols;
 using Microsoft.CodeAnalysis.GeneratedCodeRecognition;
+using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Roslyn.Utilities;
 
@@ -21,6 +23,7 @@ public static INavigableItem GetItemFromDeclaredSymbolInfo(DeclaredSymbolInfo de
             return new DeclaredSymbolNavigableItem(document, declaredSymbolInfo);
         }
 
+
         public static IEnumerable<INavigableItem> GetItemsFromPreferredSourceLocations(Solution solution, ISymbol symbol)
         {
             var locations = GetPreferredSourceLocations(solution, symbol);
@@ -57,6 +60,24 @@ private static IEnumerable<Location> GetPreferredSourceLocations(ISymbol symbol)
                 : locations.Where(loc => loc.IsInSource);
         }
 
+        public static string GetSymbolDisplayString(Project project, ISymbol symbol)
+        {
+            var symbolDisplayService = project.LanguageServices.GetRequiredService<ISymbolDisplayService>();
+            switch (symbol.Kind)
+            {
+                case SymbolKind.NamedType:
+                    return symbolDisplayService.ToDisplayString(symbol, s_shortFormatWithModifiers);
+
+                case SymbolKind.Method:
+                    return symbol.IsStaticConstructor()
+                        ? symbolDisplayService.ToDisplayString(symbol, s_shortFormatWithModifiers)
+                        : symbolDisplayService.ToDisplayString(symbol, s_shortFormat);
+
+                default:
+                    return symbolDisplayService.ToDisplayString(symbol, s_shortFormat);
+            }
+        }
+
         private static readonly SymbolDisplayFormat s_shortFormat =
             new SymbolDisplayFormat(
                 globalNamespaceStyle: SymbolDisplayGlobalNamespaceStyle.OmittedAsContaining,

src/EditorFeatures/Test/TestExportProvider.cs

@@ -96,6 +96,8 @@ private static Type[] GetNeutralAndCSharpAndVisualBasicTypes()
                 typeof(Microsoft.CodeAnalysis.VisualBasic.VisualBasicSyntaxFactsService),
                 typeof(CodeAnalysis.CSharp.CSharpSymbolDeclarationService),
                 typeof(CodeAnalysis.VisualBasic.VisualBasicSymbolDeclarationService),
+                typeof(CodeAnalysis.Editor.CSharp.LanguageServices.CSharpSymbolDisplayServiceFactory),
+                typeof(CodeAnalysis.Editor.VisualBasic.LanguageServices.VisualBasicSymbolDisplayServiceFactory),
                 typeof(CodeAnalysis.CSharp.Simplification.CSharpSimplificationService),
                 typeof(CodeAnalysis.VisualBasic.Simplification.VisualBasicSimplificationService),
                 typeof(CodeAnalysis.CSharp.Rename.CSharpRenameConflictLanguageService),