[HybridWebView] Bubble up exceptions in JS into .NET

[mattleibow]

Description of Change

Previously an exception in JS would just fail to return to .NET, leaving the tasks unfinished.

This PR makes sure to catch the exception in JS and then send it back to .NET where it is re-thrown as a .NET exception.

There is additional work to remove the task manager from the handler definition and move the logic into a new service that is registered. This will allow for better testing and/or a new handler that does not need to also use the internal interface.

By default there is no behavior change, but you can enable this AppContext Switch with one line of code in your app's MauiProgram.cs:

AppContext.SetSwitch("HybridWebView.InvokeJavaScriptThrowsExceptions", isEnabled: true);

Issues Fixed

Fixes #27097

Copilot reviewed 5 out of 9 changed files in this pull request and generated no comments.

Files not reviewed (4)

• src/Controls/tests/DeviceTests/Resources/Raw/HybridTestRoot/index.html: Language not supported
• src/Controls/src/Core/Hosting/AppHostBuilderExtensions.cs: Evaluated as low risk
• src/Controls/tests/DeviceTests/Elements/HybridWebView/HybridWebViewTests.cs: Evaluated as low risk
• src/Core/src/Handlers/HybridWebView/HybridWebViewTaskManager.cs: Evaluated as low risk

Comments suppressed due to low confidence (2)

src/Core/src/Handlers/HybridWebView/HybridWebViewHandler.cs:115

• Ensure that the new exception handling logic for '__InvokeJavaScriptFailed' is covered by tests.

case "__InvokeJavaScriptFailed":

src/Core/src/Handlers/HybridWebView/HybridWebViewTask.cs:5

• [nitpick] The term 'TaskId' is clear, but ensure that all new symbols follow the same clarity and consistency.

internal record struct HybridWebViewTask(string TaskId, TaskCompletionSource<string?> TaskCompletionSource);

[Eilon]

The code and tests look good to me. Please note my 2 comments.

[mattleibow]

/rebase

[mattleibow]

This should be behind a flag. I need to create an issue for net10 to make the switch by default to throw.