Handle completion items with leading/trailing decorative text

Leading/trailing decorative text can interfere with the pattern
matcher's ability to find/bold matching spans and add redundant items to
the MRU list.

src/EditorFeatures/Core.Wpf/Completion/Presentation/RoslynCompletionSet.cs

-using System.Collections.Generic;
+// 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.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
 using Microsoft.CodeAnalysis.Completion;
@@ -29,6 +33,8 @@ internal class RoslynCompletionSet : CompletionSet2
         protected Dictionary<CompletionItem, VSCompletion> CompletionItemMap;
         protected CompletionItem SuggestionModeItem;
 
+        private readonly Dictionary<string, string> _displayTextToBoldingTextMap = new Dictionary<string, string>();
+
         protected string FilterText;
 
         public RoslynCompletionSet(
@@ -90,6 +96,14 @@ public override void Recalculate()
         {
             _foregroundThread.AssertIsForeground();
 
+            foreach (var item in completionItems)
+            {
+                if (!_displayTextToBoldingTextMap.ContainsKey(item.DisplayText))
+                {
+                    _displayTextToBoldingTextMap.Add(item.DisplayText, CompletionHelper.GetDisplayTextForMatching(item));
+                }
+            }
+
             // Initialize the completion map to a reasonable default initial size (+1 for the builder)
             CompletionItemMap = CompletionItemMap ?? new Dictionary<CompletionItem, VSCompletion>(completionItems.Count + 1);
             FilterText = filterText;
@@ -215,6 +229,9 @@ public override IReadOnlyList<Span> GetHighlightedSpansInDisplayText(string disp
                 return null;
             }
 
+            var textForBolding = _displayTextToBoldingTextMap.TryGetValue(displayText, out var matchingText) ? matchingText : displayText;
+            Debug.Assert(displayText.Contains(textForBolding));
+
             var pattern = this.FilterText;
             if (_highlightMatchingPortions && !string.IsNullOrWhiteSpace(pattern))
             {
@@ -222,9 +239,9 @@ public override IReadOnlyList<Span> GetHighlightedSpansInDisplayText(string disp
                 if (completionHelper != null)
                 {
                     var highlightedSpans = completionHelper.GetHighlightedSpans(
-                        displayText, pattern, CultureInfo.CurrentCulture);
+                        textForBolding, pattern, CultureInfo.CurrentCulture);
 
-                    return highlightedSpans.SelectAsArray(s => s.ToSpan());
+                    return highlightedSpans.SelectAsArray(s => new Span(s.Start + Math.Max(0, displayText.IndexOf(textForBolding)), s.Length));
                 }
             }
 

src/EditorFeatures/Core/Implementation/IntelliSense/Completion/Controller.Session_FilterModel.cs

@@ -498,7 +498,7 @@ private bool IsBetterDeletionMatch(FilterResult result1, FilterResult result2)
 
             private static int GetRecentItemIndex(ImmutableArray<string> recentItems, CompletionItem item)
             {
-                var index = recentItems.IndexOf(item.DisplayText);
+                var index = recentItems.IndexOf(CompletionHelper.GetDisplayTextForMatching(item));
                 return -index;
             }
 

src/EditorFeatures/Core/Implementation/IntelliSense/Completion/Controller_Commit.cs

@@ -174,7 +174,7 @@ private CompletionProvider GetCompletionProvider(CompletionItem item)
             }
 
             // Let the completion rules know that this item was committed.
-            this.MakeMostRecentItem(item.DisplayText);
+            this.MakeMostRecentItem(CompletionHelper.GetDisplayTextForMatching(item));
         }
 
         private void SetCaretPosition(int desiredCaretPosition)

src/Features/Core/Portable/Completion/CompletionHelper.cs

@@ -19,6 +19,11 @@ internal sealed class CompletionHelper
         private static readonly CultureInfo EnUSCultureInfo = new CultureInfo("en-US");
         private readonly bool _isCaseSensitive;
 
+        // Support for completion items with extra decorative characters in their DisplayText.
+        // This allows bolding and MRU to operate on the "real" display text (without text
+        // decorations). This should be a substring of the corresponding DisplayText.
+        private static string DisplayTextForMatching = nameof(DisplayTextForMatching);
+
         public CompletionHelper(bool isCaseSensitive)
         {
             _isCaseSensitive = isCaseSensitive;
@@ -252,5 +257,8 @@ private int ComparePreselection(CompletionItem item1, CompletionItem item2)
 
             return 0;
         }
+
+        internal static string GetDisplayTextForMatching(CompletionItem item)
+            => item.Properties.TryGetValue(DisplayTextForMatching, out var displayText) ? displayText : item.DisplayText;
     }
 }