Remove directive attribute completions from element completion list.

- This removes the excess amount of directive attribute completions that show up when completing a component.
- Added a test to verify directive attributes no longer show up in element completions.

dotnet/aspnetcore#9133

Author: N. Taylor Mullen

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/DefaultTagHelperCompletionService.cs

@@ -243,6 +243,14 @@ public override ElementCompletionResult GetElementCompletions(ElementCompletionC
 
             void UpdateCompletions(string tagName, TagHelperDescriptor possibleDescriptor)
             {
+                if (possibleDescriptor.BoundAttributes.Any(boundAttribute => boundAttribute.IsDirectiveAttribute()))
+                {
+                    // This is a TagHelper that ultimately represents a DirectiveAttribute. In classic Razor TagHelper land TagHelpers with bound attribute descriptors
+                    // were valuable to show in the completion list to understand what was possible for a certain tag; however, with Blazor directive attributes stand
+                    // on their own and shouldn't be indicated at the element level completion.
+                    return;
+                }
+
                 if (!elementCompletions.TryGetValue(tagName, out var existingRuleDescriptors))
                 {
                     existingRuleDescriptors = new HashSet<TagHelperDescriptor>();

src/Razor/test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/DefaultTagHelperCompletionServiceTest.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Components;
 using Microsoft.CodeAnalysis.Razor;
 using Xunit;
 
@@ -597,6 +598,42 @@ public void GetAttributeCompletions_NoDescriptorsForTagReturnsExistingCompletion
             AssertCompletionsAreEquivalent(expectedCompletions, completions);
         }
 
+        [Fact]
+        public void GetElementCompletions_IgnoresDirectiveAttributes()
+        {
+            // Arrange
+            var documentDescriptors = new[]
+            {
+                TagHelperDescriptorBuilder.Create("BindAttribute", "TestAssembly")
+                    .TagMatchingRuleDescriptor(rule => rule.RequireTagName("input"))
+                    .BoundAttributeDescriptor(builder =>
+                    {
+                        builder.Name = "@bind";
+                        builder.AddMetadata(ComponentMetadata.Common.DirectiveAttribute, bool.TrueString);
+                    })
+                    .TagOutputHint("table")
+                    .Build(),
+            };
+            var expectedCompletions = ElementCompletionResult.Create(new Dictionary<string, HashSet<TagHelperDescriptor>>()
+            {
+                ["table"] = new HashSet<TagHelperDescriptor>(),
+            });
+
+            var existingCompletions = new[] { "table" };
+            var completionContext = BuildElementCompletionContext(
+                documentDescriptors,
+                existingCompletions,
+                containingTagName: "body",
+                containingParentTagName: null);
+            var service = CreateTagHelperCompletionFactsService();
+
+            // Act
+            var completions = service.GetElementCompletions(completionContext);
+
+            // Assert
+            AssertCompletionsAreEquivalent(expectedCompletions, completions);
+        }
+
         [Fact]
         public void GetElementCompletions_TagOutputHintDoesNotFallThroughToSchemaCheck()
         {