Refactor CompletionTriggerAndCommitCharacters

This change transforms CompletionTriggerAndCommitCharacters from being a partly static and partly instance service to being fully instance-based. Here is a summary of the changes:

- All collections are now private and operations on them are exposed via instance methods.
- I've switched from FrozenSet<string> to HashSet<char>. Honestly, I doubt we were getting much value from FrozenSet<string> for strings with the same length.
- All initialization is performed in the constructor.
- Accessing AllTriggerCharacters or AllCommitCharacters returns a new array each time to avoid modifying the original array.
- The Razor transition character ('@') is now a constant rather than a set with a single element.

Author: DustinCampbell

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Completion/RazorCompletionEndpoint.cs

@@ -25,7 +25,7 @@ internal class RazorCompletionEndpoint(
     : IRazorRequestHandler<CompletionParams, VSInternalCompletionList?>, ICapabilitiesProvider
 {
     private readonly CompletionListProvider _completionListProvider = completionListProvider;
-    private readonly CompletionTriggerAndCommitCharacters _completionTriggerAndCommitCharacters = completionTriggerAndCommitCharacters;
+    private readonly CompletionTriggerAndCommitCharacters _triggerAndCommitCharacters = completionTriggerAndCommitCharacters;
     private readonly ITelemetryReporter? _telemetryReporter = telemetryReporter;
     private readonly RazorLSPOptionsMonitor _optionsMonitor = optionsMonitor;
 
@@ -40,8 +40,8 @@ public void ApplyCapabilities(VSInternalServerCapabilities serverCapabilities, V
         serverCapabilities.CompletionProvider = new CompletionOptions()
         {
             ResolveProvider = true,
-            TriggerCharacters = _completionTriggerAndCommitCharacters.AllTriggerCharacters,
-            AllCommitCharacters = CompletionTriggerAndCommitCharacters.AllCommitCharacters
+            TriggerCharacters = _triggerAndCommitCharacters.AllTriggerCharacters,
+            AllCommitCharacters = _triggerAndCommitCharacters.AllCommitCharacters
         };
     }
 

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Completion/CompletionTriggerAndCommitCharacters.cs

@@ -1,76 +1,117 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-using System.Collections.Frozen;
-using System.Linq;
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.Razor.Workspaces;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.Razor.Completion;
 
-internal class CompletionTriggerAndCommitCharacters(LanguageServerFeatureOptions languageServerFeatureOptions)
+internal class CompletionTriggerAndCommitCharacters
 {
     /// <summary>
     ///  Trigger character that can trigger both Razor and Delegation completion
     /// </summary>
-    private const string RazorDelegationTriggerCharacter = "@";
+    private const char TransitionCharacter = '@';
 
-    private readonly LanguageServerFeatureOptions _languageServerFeatureOptions = languageServerFeatureOptions;
+    private static readonly char[] s_vsHtmlTriggerCharacters = [':', '#', '.', '!', '*', ',', '(', '[', '-', '<', '&', '\\', '/', '\'', '"', '=', ':', ' ', '`'];
+    private static readonly char[] s_vsCodeHtmlTriggerCharacters = ['#', '.', '!', ',', '-', '<'];
+    private static readonly char[] s_razorTriggerCharacters = ['<', ':', ' '];
+    private static readonly char[] s_csharpTriggerCharacters = [' ', '(', '=', '#', '.', '<', '[', '{', '"', '/', ':', '~'];
+    private static readonly char[] s_commitCharacters = [' ', '>', ';', '='];
 
-    private static readonly FrozenSet<string> s_vsHtmlTriggerCharacters = new[] { RazorDelegationTriggerCharacter, ":", "#", ".", "!", "*", ",", "(", "[", "-", "<", "&", "\\", "/", "'", "\"", "=", ":", " ", "`" }.ToFrozenSet();
-    private static readonly FrozenSet<string> s_vsCodeHtmlTriggerCharacters = new[] { RazorDelegationTriggerCharacter, "#", ".", "!", ",", "-", "<", }.ToFrozenSet();
-    private FrozenSet<string>? _allDelegationTriggerCharacters;
-    private string[]? _allTriggerCharacters;
+    private readonly HashSet<char> _csharpTriggerCharacters;
+    private readonly HashSet<char> _delegationTriggerCharacters;
+    private readonly HashSet<char> _htmlTriggerCharacters;
+    private readonly HashSet<char> _razorTriggerCharacters;
+    private readonly ImmutableArray<string> _allTriggerCharacters;
+    private readonly ImmutableArray<string> _allCommitCharacters;
 
-    private static readonly FrozenSet<string> s_razorTriggerCharacters = new[] { RazorDelegationTriggerCharacter, "<", ":", " " }.ToFrozenSet();
-    private static readonly FrozenSet<string> s_razorDelegationTriggerCharacters = new[] { RazorDelegationTriggerCharacter }.ToFrozenSet();
-    private static readonly FrozenSet<string> s_csharpTriggerCharacters = new[] { " ", "(", "=", "#", ".", "<", "[", "{", "\"", "/", ":", "~" }.ToFrozenSet();
-
-    private FrozenSet<string> HtmlTriggerCharacters =>
-        _languageServerFeatureOptions.UseVsCodeCompletionTriggerCharacters ? s_vsCodeHtmlTriggerCharacters : s_vsHtmlTriggerCharacters;
-
-    private FrozenSet<string> AllDelegationTriggerCharacters => _allDelegationTriggerCharacters
-        ??= s_razorDelegationTriggerCharacters.Union(s_csharpTriggerCharacters).Union(HtmlTriggerCharacters).ToFrozenSet();
-
-    public string[] AllTriggerCharacters => _allTriggerCharacters ??= [.. s_razorTriggerCharacters.Union(AllDelegationTriggerCharacters)];
+    // Note: Create a new array each time to avoid modifying the original array.
+    public string[] AllTriggerCharacters => [.. _allTriggerCharacters];
 
     /// <summary>
     /// This is the intersection of C# and HTML commit characters.
     /// </summary>
     // We need to specify it so that platform can correctly calculate ApplicableToSpan in
     // https://devdiv.visualstudio.com/DevDiv/_git/VSLanguageServerClient?path=/src/product/RemoteLanguage/Impl/Features/Completion/AsyncCompletionSource.cs&version=GBdevelop&line=855&lineEnd=855&lineStartColumn=9&lineEndColumn=49&lineStyle=plain&_a=contents
     // This is needed to fix https://github.com/dotnet/razor/issues/10787 in particular
-    public static string[] AllCommitCharacters = [" ", ">", ";", "="];
-
-    public static bool IsValidTrigger(FrozenSet<string> triggerCharacters, CompletionContext completionContext)
-        => completionContext.TriggerKind != CompletionTriggerKind.TriggerCharacter ||
-           completionContext.TriggerCharacter is null ||
-           triggerCharacters.Contains(completionContext.TriggerCharacter);
+    // Note: Create a new array each time to avoid modifying the original array.
+    public string[] AllCommitCharacters => [.. _allCommitCharacters];
+
+    public CompletionTriggerAndCommitCharacters(LanguageServerFeatureOptions languageServerFeatureOptions)
+    {
+        // C# trigger characters (do NOT include '@')
+        var csharpTriggerCharacters = new HashSet<char>();
+        csharpTriggerCharacters.UnionWith(s_csharpTriggerCharacters);
+
+        // HTML trigger characters (include '@' + HTML trigger characters)
+        var htmlTriggerCharacters = new HashSet<char>() { TransitionCharacter };
+
+        if (languageServerFeatureOptions.UseVsCodeCompletionTriggerCharacters)
+        {
+            htmlTriggerCharacters.UnionWith(s_vsCodeHtmlTriggerCharacters);
+        }
+        else
+        {
+            htmlTriggerCharacters.UnionWith(s_vsHtmlTriggerCharacters);
+        }
+
+        // Delegation trigger characters (include '@' + C# and HTML trigger characters)
+        var delegationTriggerCharacters = new HashSet<char> { TransitionCharacter };
+        delegationTriggerCharacters.UnionWith(csharpTriggerCharacters);
+        delegationTriggerCharacters.UnionWith(htmlTriggerCharacters);
+
+        // Razor trigger characters (include '@' + Razor trigger characters)
+        var razorTriggerCharacters = new HashSet<char>() { TransitionCharacter };
+        razorTriggerCharacters.UnionWith(s_razorTriggerCharacters);
+
+        // All trigger characters (include Razor + Delegation trigger characters)
+        var allTriggerCharacters = new HashSet<char>();
+        allTriggerCharacters.UnionWith(razorTriggerCharacters);
+        allTriggerCharacters.UnionWith(delegationTriggerCharacters);
+
+        var commitCharacters = new HashSet<char>();
+        commitCharacters.UnionWith(s_commitCharacters);
+
+        _csharpTriggerCharacters = csharpTriggerCharacters;
+        _htmlTriggerCharacters = htmlTriggerCharacters;
+        _razorTriggerCharacters = razorTriggerCharacters;
+        _delegationTriggerCharacters = delegationTriggerCharacters;
+        _allTriggerCharacters = allTriggerCharacters.SelectAsArray(static c => c.ToString());
+        _allCommitCharacters = commitCharacters.SelectAsArray(static c => c.ToString());
+    }
 
     public bool IsValidCSharpTrigger(CompletionContext completionContext)
-        => IsValidTrigger(s_csharpTriggerCharacters, completionContext);
+        => IsValidTrigger(completionContext, _csharpTriggerCharacters);
 
     public bool IsValidDelegationTrigger(CompletionContext completionContext)
-        => IsValidTrigger(AllDelegationTriggerCharacters, completionContext);
+        => IsValidTrigger(completionContext, _delegationTriggerCharacters);
 
     public bool IsValidHtmlTrigger(CompletionContext completionContext)
-        => IsValidTrigger(HtmlTriggerCharacters, completionContext);
+        => IsValidTrigger(completionContext, _htmlTriggerCharacters);
 
     public bool IsValidRazorTrigger(CompletionContext completionContext)
-        => IsValidTrigger(s_razorTriggerCharacters, completionContext);
+        => IsValidTrigger(completionContext, _razorTriggerCharacters);
+
+    private static bool IsValidTrigger(CompletionContext completionContext, HashSet<char> triggerCharacters)
+        => completionContext.TriggerKind != CompletionTriggerKind.TriggerCharacter ||
+           completionContext.TriggerCharacter is not [var c] ||
+           triggerCharacters.Contains(c);
 
     public bool IsCSharpTriggerCharacter(string ch)
-        => s_csharpTriggerCharacters.Contains(ch);
+        => ch is [var c] && _csharpTriggerCharacters.Contains(c);
 
     public bool IsDelegationTriggerCharacter(string ch)
-        => AllDelegationTriggerCharacters.Contains(ch);
+        => ch is [var c] && _delegationTriggerCharacters.Contains(c);
 
     public bool IsHtmlTriggerCharacter(string ch)
-        => HtmlTriggerCharacters.Contains(ch);
+        => ch is [var c] && _htmlTriggerCharacters.Contains(c);
 
     public bool IsRazorTriggerCharacter(string ch)
-        => s_razorTriggerCharacters.Contains(ch);
+        => ch is [var c] && _razorTriggerCharacters.Contains(c);
 
-    public bool IsRazorDelegationTriggerCharacter(string ch)
-        => ch == RazorDelegationTriggerCharacter;
+    public bool IsTransitionCharacter(string ch)
+        => ch is [TransitionCharacter];
 }

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

@@ -80,7 +80,7 @@ internal static class DelegatedCompletionHelper
         };
 
         if (languageKind == RazorLanguageKind.CSharp
-            && triggerAndCommitCharacters.IsRazorDelegationTriggerCharacter(triggerCharacter))
+            && triggerAndCommitCharacters.IsTransitionCharacter(triggerCharacter))
         {
             // The C# language server will not return any completions for the '@' character unless we
             // send the completion request explicitly.

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentCompletionEndpoint.cs

@@ -69,7 +69,7 @@ public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilitie
                 {
                     ResolveProvider = false, // TODO - change to true when Resolve is implemented
                     TriggerCharacters = _triggerAndCommitCharacters.AllTriggerCharacters,
-                    AllCommitCharacters = CompletionTriggerAndCommitCharacters.AllCommitCharacters
+                    AllCommitCharacters = _triggerAndCommitCharacters.AllCommitCharacters
                 }
             }];
         }