Interceptor for AmbientLoggerFactory

[nickrandolph]

Add the ability to intercept when the AmbientLoggerFactory is set by an app

[Copilot]

Pull request overview

This PR adds a new extension point to Uno.Extensions.LogExtensionPoint allowing hosts to intercept and potentially wrap/replace the AmbientLoggerFactory whenever an app sets it, along with a new MSTest suite validating the expected behaviors.

Changes:

• Added a configurable RegisterFactoryInterceptor(...) hook invoked when AmbientLoggerFactory is set.
• Updated the AmbientLoggerFactory setter to apply the interceptor result before storing.
• Added LogExtensionPointTests and updated the tests project to reference the singleton logging extensions project.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/Uno.Core.Tests/Uno.Core.Tests.csproj	Adds project reference needed to test the new singleton logging extension behavior.
src/Uno.Core.Tests/LogExtensionPointTests.cs	Introduces new tests covering interceptor registration and AmbientLoggerFactory behavior.
src/Uno.Core.Extensions.Logging.Singleton/LogExtensionPoint.cs	Adds interceptor API and wires it into the ambient factory setter.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[nickrandolph]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied all changes from the review threads in commit 04bd533:

• Thread 1 (multiple interceptor invocations): switched the setter from Transactional.Update to Volatile.Read/Volatile.Write, so the interceptor runs exactly once per assignment.
• Thread 2 (ambiguous contract): changed the interceptor delegate to Func<ILoggerFactory?, ILoggerFactory, ILoggerFactory>? — both proposed and the return type are non-nullable, enforced at compile time.
• Thread 3 (inaccurate test): replaced RegisterFactoryInterceptor_InterceptorCanReturnNull_FallsBackToGetFactory with RegisterFactoryInterceptor_InterceptorMustReturnNonNull (validates the non-null contract) and added AmbientLoggerFactory_Set_InterceptorRunsOnceEvenUnderContention to validate the single-invocation behavior.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ nickrandolph
❌ Copilot
_{You have signed the CLA already but the status is still pending? Let us recheck it.}