Fixed the ErrorBoundary multiple errors bug

[dariatiurina]

Fixed the ErrorBoundary multiple errors bug

Description

This pull request enhances error handling in Blazor components, especially around error boundaries and faulted tasks during component initialization and rendering. It introduces new tests and supporting components to ensure that exceptions thrown in lifecycle methods or during rendering are correctly captured by error boundaries, and that error boundaries can handle multiple simultaneous errors.

Changes:

• Modified ComponentBase to avoid calling StateHasChanged when the initialization task is faulted, preventing unnecessary state updates after errors.
• Added new test in ComponentBaseTest.cs to verify that error boundary capture exceptions from faulted tasks in OnInitializedAsync and during rendering, and that these errors are surfaced correctly.
• Introduced TestErrorBoundary and TestComponentErrorBuildRenderTree test components to simulate and verify error boundary behavior with faulted tasks and rendering errors.

Fixes #39814

[Copilot]

Pull Request Overview

This pull request fixes a bug in Blazor's ErrorBoundary handling where multiple simultaneous errors could cause issues. The fix prevents unnecessary state updates when component initialization tasks are faulted, improving error boundary behavior.

Key changes:

• Modified ComponentBase to skip StateHasChanged() calls when initialization tasks are faulted
• Added comprehensive test coverage for error boundary scenarios with multiple errors
• Created test components to simulate and verify error boundary behavior with faulted tasks

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Components/Components/src/ComponentBase.cs	Added condition to prevent StateHasChanged when initialization task is faulted
src/Components/Components/test/ComponentBaseTest.cs	Added unit test and helper components for error boundary testing
src/Components/test/testassets/BasicTestApp/ErrorBoundaryTest/MultipleErrorsChild.razor	New test component that throws errors in both OnInitializedAsync and BuildRenderTree
src/Components/test/testassets/BasicTestApp/ErrorBoundaryTest/ErrorBoundaryCases.razor	Added UI test case for multiple errors scenario
src/Components/test/E2ETest/Tests/ErrorBoundaryTest.cs	Added E2E test for multiple errors handling

[javiercn]

Looks great, minor comments about a case we missed and a couple extra tests to capture the new behavior.

Good job!

[ScarletKuro]

This probably should be marked as breaking change, see MudBlazor/MudBlazor#12098 (comment)
This change affects userspace, since some frameworks depended on the previous behavior, which effectively made it a feature rather than a bug. This change should be documented in https://learn.microsoft.com/en-us/dotnet/core/compatibility/10.0 if there are no plans to reverse it.

[javiercn]

@ScarletKuro please file a new issue with the problem. We won't effectively track comments on closed PRs. Please also detail the concrete use case in which this change represents a problem with MudBlazor