Ensure action is only offered on the name portion of the attribute

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/Razor/UnboundDirectiveAttributeAddUsingCodeActionProvider.cs

@@ -49,6 +49,13 @@ public Task<ImmutableArray<RazorVSInternalCodeAction>> ProvideAsync(RazorCodeAct
             return SpecializedTasks.EmptyImmutableArray<RazorVSInternalCodeAction>();
         }
 
+        // Make sure the cursor is actually on the name part, since the attribute block is the whole attribute, including
+        // value and even some whitespace
+        if (!attributeBlock.Name.Span.Contains(context.StartAbsoluteIndex))
+        {
+            return SpecializedTasks.EmptyImmutableArray<RazorVSInternalCodeAction>();
+        }
+
         // Try to find the missing namespace for this directive attribute
         if (!TryGetMissingDirectiveAttributeNamespace(context.CodeDocument, attributeBlock, out var missingNamespace))
         {

src/Razor/test/Microsoft.VisualStudioCode.RazorExtension.Test/Endpoints/Shared/CodeActions/UnboundDirectiveAttributeAddUsingTests.cs

@@ -93,6 +93,16 @@ public async Task NoCodeAction_WhenNotOnDirectiveAttribute()
         await VerifyCodeActionAsync(input, expected: null, LanguageServerConstants.CodeActions.AddUsing, addDefaultImports: false);
     }
 
+    [Fact]
+    public async Task NoCodeAction_WhenNotOnAttributeName()
+    {
+        var input = """
+            <input @onchange="HandleCha[||]nge" />
+            """;
+
+        await VerifyCodeActionAsync(input, expected: null, LanguageServerConstants.CodeActions.AddUsing, addDefaultImports: false);
+    }
+
     [Fact]
     public async Task AddUsing_Bind()
     {