Document breaking change: FileConfigurationSource.OnLoadException now observes IO errors

[Copilot]

In .NET 11 Preview 7, a bug fix unified error handling in FileConfigurationProvider and its derivatives, so IO errors (e.g., from AddJsonFile, AddXmlFile, AddIniFile, or file reloads) are now forwarded to FileConfigurationSource.OnLoadException instead of only being observable via TaskScheduler.UnobservedTaskException. Code that unconditionally casts the exception in OnLoadException to InvalidDataException or FileNotFoundException can now throw InvalidCastException.

Changes

• Added new breaking change article docs/core/compatibility/extensions/11/fileconfigurationsource-onloadexception-io-errors.md covering previous/new behavior, reason for change, and recommended action.
• Registered the article in docs/core/compatibility/toc.yml under .NET 11 > Extensions.
• Added a row for the article in the .NET 11 breaking changes index (docs/core/compatibility/11.md).

Example from the article

options.OnLoadException = context =>
{
    // Handle any exception type, not just InvalidDataException or FileNotFoundException.
    if (context.Exception is IOException ioException)
    {
        // Handle IO errors.
    }
    else if (context.Exception is InvalidDataException invalidDataException)
    {
        // Handle parsing errors.
    }

    context.Ignore = true;
};

• Fixes [Breaking change]: FileConfigurationSource.OnLoadException callback is called for IO errors #55022

---

Internal previews

File	Preview link
docs/core/compatibility/11.md	docs/core/compatibility/11
docs/core/compatibility/extensions/11/fileconfigurationsource-onloadexception-io-errors.md	docs/core/compatibility/extensions/11/fileconfigurationsource-onloadexception-io-errors
docs/core/compatibility/toc.yml	docs/core/compatibility/toc

[Copilot]

Copilot wasn't able to review any files in this pull request.