Append aria-describedby tokens instead of overwriting

- Add TagHelperOutputExtensions.AppendAriaDescribedby helper that preserves caller-supplied tokens (space-separated id list) and dedupes
- Replace SetAttribute calls in AddInfoTextId/GetInfoAsHtml of abp-input/abp-select with the helper
- Cover the consumer-provided aria-describedby case with a new test

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/TagHelperOutputExtensions.cs

@@ -1,5 +1,7 @@
 using Microsoft.AspNetCore.Razor.TagHelpers;
+using System;
 using System.IO;
+using System.Linq;
 using System.Text.Encodings.Web;
 
 namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Extensions;
@@ -14,4 +16,34 @@ public static class TagHelperOutputExtensions
             return writer.ToString();
         }
     }
+
+    /// <summary>
+    /// Appends an id token to the space-separated <c>aria-describedby</c> attribute,
+    /// preserving any tokens that were already present (e.g. provided by the consumer)
+    /// and skipping the token when it is already in the list.
+    /// </summary>
+    public static void AppendAriaDescribedby(this TagHelperOutput output, string token)
+    {
+        if (string.IsNullOrEmpty(token))
+        {
+            return;
+        }
+
+        var existing = output.Attributes
+            .FirstOrDefault(a => a.Name == "aria-describedby")?.Value?.ToString();
+
+        if (string.IsNullOrEmpty(existing))
+        {
+            output.Attributes.SetAttribute("aria-describedby", token);
+            return;
+        }
+
+        var tokens = existing.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+        if (tokens.Any(t => t == token))
+        {
+            return;
+        }
+
+        output.Attributes.SetAttribute("aria-describedby", existing + " " + token);
+    }
 }

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelperService.cs

@@ -266,7 +266,7 @@ public class AbpInputTagHelperService : AbpTagHelperService<AbpInputTagHelper>
             return;
         }
 
-        inputTagHelperOutput.Attributes.SetAttribute("aria-describedby", idValue + "InfoText");
+        inputTagHelperOutput.AppendAriaDescribedby(idValue + "InfoText");
     }
 
     protected virtual bool IsInputCheckbox(TagHelperContext context, TagHelperOutput output, TagHelperAttributeList attributes)
@@ -365,7 +365,7 @@ public class AbpInputTagHelperService : AbpTagHelperService<AbpInputTagHelper>
         if (!string.IsNullOrEmpty(idValue))
         {
             div.Attributes.Add("id", idValue + "InfoText");
-            inputTag.Attributes.SetAttribute("aria-describedby", idValue + "InfoText");
+            inputTag.AppendAriaDescribedby(idValue + "InfoText");
         }
 
         return div.ToHtmlString();

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelperService.cs

@@ -223,7 +223,7 @@ public class AbpSelectTagHelperService : AbpTagHelperService<AbpSelectTagHelper>
             return;
         }
 
-        inputTagHelperOutput.Attributes.SetAttribute("aria-describedby", idValue + "InfoText");
+        inputTagHelperOutput.AppendAriaDescribedby(idValue + "InfoText");
     }
 
     protected virtual string GetInfoAsHtml(TagHelperContext context, TagHelperOutput output, TagHelperOutput inputTag)
@@ -258,7 +258,7 @@ public class AbpSelectTagHelperService : AbpTagHelperService<AbpSelectTagHelper>
         if (!string.IsNullOrEmpty(idValue))
         {
             div.Attributes.Add("id", idValue + "InfoText");
-            inputTag.Attributes.SetAttribute("aria-describedby", idValue + "InfoText");
+            inputTag.AppendAriaDescribedby(idValue + "InfoText");
         }
 
         return div.ToHtmlString();

framework/test/Volo.Abp.AspNetCore.Mvc.UI.Tests/Volo/Abp/AspNetCore/Mvc/UI/Bootstrap/TagHelpers/Form/AbpSelectTagHelperService_Tests.cs

@@ -78,6 +78,25 @@ public class AbpSelectTagHelperService_Tests
         service.LastSelectTag!.Attributes.ContainsName("aria-describedby").ShouldBeFalse();
     }
 
+    [Fact]
+    public async Task Aria_describedby_should_preserve_existing_value_set_by_caller()
+    {
+        var service = new TestAbpSelectTagHelperService(existingAriaDescribedby: "custom-id");
+        var tagHelper = new AbpSelectTagHelper(service)
+        {
+            AspFor = CreateModelExpression(),
+            InfoText = "Description"
+        };
+
+        var output = CreateOutput();
+
+        await tagHelper.ProcessAsync(CreateContext(), output);
+
+        service.LastSelectTag.ShouldNotBeNull();
+        service.LastSelectTag!.Attributes["aria-describedby"].Value.ToString().ShouldBe("custom-id TestSelectInfoText");
+        service.LastGroupHtml.ShouldContain("aria-describedby=\"custom-id TestSelectInfoText\"");
+    }
+
     [Fact]
     public async Task InputInfoText_attribute_should_render_info_text_with_single_aria_describedby()
     {
@@ -143,15 +162,17 @@ public class AbpSelectTagHelperService_Tests
     private sealed class TestAbpSelectTagHelperService : AbpSelectTagHelperService
     {
         private readonly string? _selectId;
+        private readonly string? _existingAriaDescribedby;
 
         public string LastGroupHtml { get; private set; } = string.Empty;
 
         public TagHelperOutput? LastSelectTag { get; private set; }
 
-        public TestAbpSelectTagHelperService(string? selectId = "TestSelect")
+        public TestAbpSelectTagHelperService(string? selectId = "TestSelect", string? existingAriaDescribedby = null)
             : base(null!, HtmlEncoder.Default, new FakeTagHelperLocalizer(), null!, null!)
         {
             _selectId = selectId;
+            _existingAriaDescribedby = existingAriaDescribedby;
         }
 
         protected override Task<TagHelperOutput> GetSelectTagAsync(TagHelperContext context, TagHelperOutput output, TagHelperContent childContent)
@@ -161,6 +182,10 @@ public class AbpSelectTagHelperService_Tests
             {
                 attributes.Add("id", _selectId);
             }
+            if (!string.IsNullOrEmpty(_existingAriaDescribedby))
+            {
+                attributes.Add("aria-describedby", _existingAriaDescribedby);
+            }
 
             LastSelectTag = new TagHelperOutput(
                 "select",