Address review comments

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/CompletionSource.cs

@@ -408,9 +408,13 @@ static void AddPropertiesToSession(IAsyncCompletionSession session, CompletionLi
         /// calculation cost for cached Roslyn completion items.
         /// FilterSetData is the bit vector value from the FilterSet of this item.
         /// </summary>
-        private readonly record struct VSCompletionItemData
-            (string DisplayText, ImageElement Icon, ImmutableArray<AsyncCompletionData.CompletionFilter> Filters,
-                int FilterSetData, ImmutableArray<ImageElement> AttributeIcons, string InsertionText);
+        private readonly record struct VSCompletionItemData(
+            string DisplayText,
+            ImageElement Icon,
+            ImmutableArray<AsyncCompletionData.CompletionFilter> Filters,
+            int FilterSetData,
+            ImmutableArray<ImageElement> AttributeIcons,
+            string InsertionText);
 
         private VSCompletionItem Convert(
             Document document,

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/ItemManager.CompletionListUpdater.cs

@@ -407,11 +407,6 @@ private void AddCompletionItems(List<MatchResult<VSCompletionItem>> list, Cancel
 
             private ImmutableArray<CompletionItemWithHighlight> GetHighlightedList(IReadOnlyList<MatchResult<VSCompletionItem>> items, CancellationToken cancellationToken)
             {
-                if (items.IsEmpty())
-                {
-                    return ImmutableArray<CompletionItemWithHighlight>.Empty;
-                }
-
                 using var _ = ArrayBuilder<CompletionItemWithHighlight>.GetInstance(items.Count, out var builder);
                 builder.AddRange(items.Select(matchResult =>
                 {

src/EditorFeatures/TestUtilities/Completion/AbstractCompletionProviderTests.cs

@@ -74,7 +74,7 @@ private CompletionOptions GetCompletionOptions()
                 options = options with { ShowItemsFromUnimportedNamespaces = ShowImportCompletionItemsOptionValue.Value };
 
             if (ForceExpandedCompletionIndexCreation.HasValue)
-                options = options with { ForceExpandedCompletionIndexCreation = true };
+                options = options with { ForceExpandedCompletionIndexCreation = ForceExpandedCompletionIndexCreation.Value };
 
             if (HideAdvancedMembers.HasValue)
                 options = options with { HideAdvancedMembers = HideAdvancedMembers.Value };

src/Features/Core/Portable/Completion/CompletionServiceWithProviders.ProviderManager.cs

@@ -24,18 +24,17 @@ public abstract partial class CompletionServiceWithProviders
         private sealed class ProviderManager : IEqualityComparer<ImmutableHashSet<string>>
         {
             private readonly object _gate = new();
+            private readonly Dictionary<string, CompletionProvider?> _nameToProvider = new();
+            private readonly Dictionary<ImmutableHashSet<string>, ImmutableArray<CompletionProvider>> _rolesToProviders;
 
-            private readonly ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, StrongBox<ImmutableArray<CompletionProvider>>> _projectCompletionProvidersMap
-                 = new();
-
-            private readonly ConditionalWeakTable<AnalyzerReference, ProjectCompletionProvider> _analyzerReferenceToCompletionProvidersMap
-                = new();
+            // Following CWTs are used to cache completion providers from projects' references,
+            // so we can avoid the slow path unless there's any change to the references.
+            private readonly ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, StrongBox<ImmutableArray<CompletionProvider>>> _projectCompletionProvidersMap = new();
+            private readonly ConditionalWeakTable<AnalyzerReference, ProjectCompletionProvider> _analyzerReferenceToCompletionProvidersMap = new();
 
             private readonly ConditionalWeakTable<AnalyzerReference, ProjectCompletionProvider>.CreateValueCallback _createProjectCompletionProvidersProvider
                 = new(r => new ProjectCompletionProvider(r));
 
-            private readonly Dictionary<string, CompletionProvider?> _nameToProvider = new();
-            private readonly Dictionary<ImmutableHashSet<string>, ImmutableArray<CompletionProvider>> _rolesToProviders;
             private readonly Func<ImmutableHashSet<string>, ImmutableArray<CompletionProvider>> _createRoleProviders;
             private readonly Func<string, CompletionProvider?> _getProviderByName;