Extract out helper code to a common location.

src/EditorFeatures/Core/EditorFeatures.csproj

@@ -109,6 +109,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="FindUsages\FindUsagesContext.cs" />
+    <Compile Include="FindUsages\FindUsagesHelpers.cs" />
     <Compile Include="FindUsages\IFindUsagesContext.cs" />
     <Compile Include="Implementation\NavigateTo\AbstractNavigateToItemDisplay.cs" />
     <Compile Include="CommandArgs.cs" />

src/EditorFeatures/Core/FindReferences/AbstractFindReferencesService.cs

@@ -3,13 +3,12 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editor.FindUsages;
 using Microsoft.CodeAnalysis.Editor.Host;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
-using Microsoft.CodeAnalysis.Editor.SymbolMapping;
-using Microsoft.CodeAnalysis.FindUsages;
 using Microsoft.CodeAnalysis.FindSymbols;
+using Microsoft.CodeAnalysis.FindUsages;
 using Microsoft.CodeAnalysis.Navigation;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Roslyn.Utilities;
@@ -30,54 +29,20 @@ internal abstract partial class AbstractFindReferencesService :
             _navigableItemPresenters = navigableItemPresenters;
         }
 
-        /// <summary>
-        /// Common helper for both the synchronous and streaming versions of FAR. 
-        /// It returns the symbol we want to search for and the solution we should
-        /// be searching.
-        /// 
-        /// Note that the <see cref="Solution"/> returned may absolutely *not* be
-        /// the same as <code>document.Project.Solution</code>.  This is because 
-        /// there may be symbol mapping involved (for example in Metadata-As-Source
-        /// scenarios).
-        /// </summary>
-        private async Task<Tuple<ISymbol, Project>> GetRelevantSymbolAndProjectAtPositionAsync(
-            Document document, int position, CancellationToken cancellationToken)
-        {
-            cancellationToken.ThrowIfCancellationRequested();
-
-            var symbol = await SymbolFinder.FindSymbolAtPositionAsync(document, position, cancellationToken: cancellationToken).ConfigureAwait(false);
-            if (symbol == null)
-            {
-                return null;
-            }
-
-            // If this document is not in the primary workspace, we may want to search for results
-            // in a solution different from the one we started in. Use the starting workspace's
-            // ISymbolMappingService to get a context for searching in the proper solution.
-            var mappingService = document.Project.Solution.Workspace.Services.GetService<ISymbolMappingService>();
-
-            var mapping = await mappingService.MapSymbolAsync(document, symbol, cancellationToken).ConfigureAwait(false);
-            if (mapping == null)
-            {
-                return null;
-            }
-
-            return Tuple.Create(mapping.Symbol, mapping.Project);
-        }
-
         private async Task<Tuple<IEnumerable<ReferencedSymbol>, Solution>> FindReferencedSymbolsAsync(
             Document document, int position, IWaitContext waitContext)
         {
             var cancellationToken = waitContext.CancellationToken;
 
-            var symbolAndProject = await GetRelevantSymbolAndProjectAtPositionAsync(document, position, cancellationToken).ConfigureAwait(false);
+            var symbolAndProject = await FindUsagesHelpers.GetRelevantSymbolAndProjectAtPositionAsync(
+                document, position, cancellationToken).ConfigureAwait(false);
             if (symbolAndProject == null)
             {
                 return null;
             }
 
-            var symbol = symbolAndProject.Item1;
-            var project = symbolAndProject.Item2;
+            var symbol = symbolAndProject?.symbol;
+            var project = symbolAndProject?.project;
 
             var displayName = GetDisplayName(symbol);
 
@@ -164,15 +129,15 @@ private bool TryDisplayReferences(Tuple<IEnumerable<ReferencedSymbol>, Solution>
             cancellationToken.ThrowIfCancellationRequested();
 
             // Find the symbol we want to search and the solution we want to search in.
-            var symbolAndProject = await GetRelevantSymbolAndProjectAtPositionAsync(
+            var symbolAndProject = await FindUsagesHelpers.GetRelevantSymbolAndProjectAtPositionAsync(
                 document, position, cancellationToken).ConfigureAwait(false);
             if (symbolAndProject == null)
             {
                 return null;
             }
 
-            var symbol = symbolAndProject.Item1;
-            var project = symbolAndProject.Item2;
+            var symbol = symbolAndProject?.symbol;
+            var project = symbolAndProject?.project;
 
             var displayName = GetDisplayName(symbol);
             context.SetSearchLabel(displayName);

src/EditorFeatures/Core/FindUsages/FindUsagesHelpers.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editor.SymbolMapping;
+using Microsoft.CodeAnalysis.FindSymbols;
+
+namespace Microsoft.CodeAnalysis.Editor.FindUsages
+{
+    internal static class FindUsagesHelpers
+    {
+        /// <summary>
+        /// Common helper for both the synchronous and streaming versions of FAR. 
+        /// It returns the symbol we want to search for and the solution we should
+        /// be searching.
+        /// 
+        /// Note that the <see cref="Solution"/> returned may absolutely *not* be
+        /// the same as <code>document.Project.Solution</code>.  This is because 
+        /// there may be symbol mapping involved (for example in Metadata-As-Source
+        /// scenarios).
+        /// </summary>
+        public static async Task<(ISymbol symbol, Project project)?> GetRelevantSymbolAndProjectAtPositionAsync(
+            Document document, int position, CancellationToken cancellationToken)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            var symbol = await SymbolFinder.FindSymbolAtPositionAsync(document, position, cancellationToken: cancellationToken).ConfigureAwait(false);
+            if (symbol == null)
+            {
+                return null;
+            }
+
+            // If this document is not in the primary workspace, we may want to search for results
+            // in a solution different from the one we started in. Use the starting workspace's
+            // ISymbolMappingService to get a context for searching in the proper solution.
+            var mappingService = document.Project.Solution.Workspace.Services.GetService<ISymbolMappingService>();
+
+            var mapping = await mappingService.MapSymbolAsync(document, symbol, cancellationToken).ConfigureAwait(false);
+            if (mapping == null)
+            {
+                return null;
+            }
+
+            return (mapping.Symbol, mapping.Project);
+        }
+    }
+}
\ No newline at end of file

src/Features/Core/Portable/Shared/TestHooks/FeatureAttribute_Names.cs

@@ -9,15 +9,20 @@ internal partial class FeatureAttribute
         public const string BraceHighlighting = nameof(BraceHighlighting);
         public const string CallHierarchy = nameof(CallHierarchy);
         public const string Classification = nameof(Classification);
+        public const string CodeModel = nameof(CodeModel);
         public const string CompletionSet = nameof(CompletionSet);
         public const string DesignerAttribute = nameof(DesignerAttribute);
-        public const string ErrorSquiggles = nameof(ErrorSquiggles);
+        public const string DiagnosticService = nameof(DiagnosticService);
         public const string ErrorList = nameof(ErrorList);
-        public const string FindReferences = nameof(FindReferences);
-        public const string TodoCommentList = nameof(TodoCommentList);
+        public const string ErrorSquiggles = nameof(ErrorSquiggles);
         public const string EventHookup = nameof(EventHookup);
+        public const string FindReferences = nameof(FindReferences);
+        public const string GlobalOperation = nameof(GlobalOperation);
+        public const string GoToImplementation = nameof(GoToImplementation);
         public const string GraphProvider = nameof(GraphProvider);
+        public const string InfoBar = nameof(InfoBar);
         public const string KeywordHighlighting = nameof(KeywordHighlighting);
+        public const string LightBulb = nameof(LightBulb);
         public const string LineSeparators = nameof(LineSeparators);
         public const string NavigateTo = nameof(NavigateTo);
         public const string NavigationBar = nameof(NavigationBar);
@@ -26,15 +31,11 @@ internal partial class FeatureAttribute
         public const string ReferenceHighlighting = nameof(ReferenceHighlighting);
         public const string Rename = nameof(Rename);
         public const string RenameTracking = nameof(RenameTracking);
+        public const string RuleSetEditor = nameof(RuleSetEditor);
         public const string SignatureHelp = nameof(SignatureHelp);
         public const string Snippets = nameof(Snippets);
         public const string SolutionCrawler = nameof(SolutionCrawler);
+        public const string TodoCommentList = nameof(TodoCommentList);
         public const string Workspace = nameof(Workspace);
-        public const string LightBulb = nameof(LightBulb);
-        public const string CodeModel = nameof(CodeModel);
-        public const string GlobalOperation = nameof(GlobalOperation);
-        public const string DiagnosticService = nameof(DiagnosticService);
-        public const string RuleSetEditor = nameof(RuleSetEditor);
-        public const string InfoBar = nameof(InfoBar);
     }
 }