fix(BootstrapBlazorErrorBoundary): improve BuildRenderTree logic to render error or fallback content (#6113)

- Only renders ChildContent when there is no exception.
- Renders custom ErrorContent if provided, otherwise renders default error content.

Author: flyliononline

src/BootstrapBlazor/Components/ErrorLogger/BootstrapBlazorErrorBoundary.cs

@@ -12,7 +12,7 @@ namespace BootstrapBlazor.Components;
 /// <summary>
 /// 内部使用 自定义异常组件
 /// </summary>
-class BootstrapBlazorErrorBoundary : ErrorBoundaryBase
+public class BootstrapBlazorErrorBoundary : ErrorBoundaryBase
 {
     [Inject]
     [NotNull]
@@ -68,19 +68,18 @@ protected override async Task OnErrorAsync(Exception exception)
     /// <param name="builder"></param>
     protected override void BuildRenderTree(RenderTreeBuilder builder)
     {
-#if DEBUG
-        // DEBUG 模式下显示异常堆栈信息到 UI 页面方便开发人员调试
-        if (OnErrorHandleAsync == null)
+        if (CurrentException is null)
         {
-            var ex = CurrentException ?? _exception;
-            if (ex != null)
-            {
-                _exception = null;
-                builder.AddContent(0, ExceptionContent(ex));
-            }
+            builder.AddContent(0, ChildContent);
+        }
+        else if (ErrorContent is not null)
+        {
+            builder.AddContent(1, ErrorContent(CurrentException));
+        }
+        else
+        {
+            builder.AddContent(2, ExceptionContent(CurrentException));
         }
-#endif
-        builder.AddContent(1, ChildContent);
     }
 
     private Exception? _exception = null;

test/UnitTest/Components/BootstrapBlazorErrorBoundaryTest.cs

@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License
+// See the LICENSE file in the project root for more information.
+// Maintainer: Argo Zhang([email protected]) Website: https://www.blazor.zone
+
+namespace UnitTest.Components;
+
+public class BootstrapBlazorErrorBoundaryTest : BootstrapBlazorTestBase
+{
+    // 1. Test rendering of child content when there is no exception
+    [Fact]
+    public void ShouldRenderChildContent_WhenNoException()
+    {
+        var cut = Context.RenderComponent<BootstrapBlazorErrorBoundary>(parameters => parameters
+            .AddChildContent("<p>Normal Content</p>")
+        );
+        cut.MarkupMatches("<p>Normal Content</p>");
+    }
+
+    // 2. Test rendering custom error content when an exception is thrown and ErrorContent is set
+    [Fact]
+    public void ShouldRenderCustomErrorContent_WhenExceptionOccurs()
+    {
+        var errorContentRendered = false;
+
+        var cut = Context.RenderComponent<BootstrapBlazorErrorBoundary>(parameters => parameters
+            .Add(p => p.ErrorContent, ex => builder =>
+            {
+                errorContentRendered = true;
+                builder.OpenElement(0, "div");
+                builder.AddAttribute(1, "class", "custom-error");
+                builder.AddContent(2, $"Custom error caught: {ex.Message}");
+                builder.CloseElement();
+            })
+            .AddChildContent<ExceptionThrowingComponent>()
+        );
+
+        cut.MarkupMatches("""<div class="custom-error">Custom error caught: Boom!</div>""");
+        Assert.True(errorContentRendered);
+    }
+
+    // 3. Test rendering default error content when an exception is thrown and ErrorContent is null
+    [Fact]
+    public void ShouldRenderDefaultExceptionContent_WhenExceptionOccurs_AndErrorContentIsNull()
+    {
+        var cut = Context.RenderComponent<BootstrapBlazorErrorBoundary>(parameters => parameters
+            .AddChildContent<ExceptionThrowingComponent>()
+        );
+        Assert.Contains("Boom!", cut.Markup);
+    }
+
+    private class ExceptionThrowingComponent : ComponentBase
+    {
+        protected override void OnInitialized()
+        {
+            throw new InvalidOperationException("Boom!");
+        }
+    }
+}
+