fix: allow XAML HR when debugging with mono runtime

[spouliot]

GitHub Issue: closes https://github.com/unoplatform/uno.vscode/issues/1240

PR Type:

• 🐞 Bugfix

What is the current behavior? 🤔

When debugging with the mono runtime (e.g. iOS and Android) Hot Reload might not always work, e.g. modifying XAML.

What is the new behavior? 🚀

Hot Reload should always work, when debugging or not, whatever the runtime.

PR Checklist ✅

Please check if your PR fulfills the following requirements:

• 📝 Commits must be following the Conventional Commits specification.
• 🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
• 📚 Docs have been added/updated which fit documentation template (for bug fixes / features)
• 🖼️ Validated PR Screenshots Compare Test Run results.
• ❗ Contains NO breaking changes

Other information ℹ️

• use AsSpan instead of ToArray to reduce memory allocations
• skip the creation of a MemoryStream and a BinaryWriter when the array is empty
• needs more testing so it's a draft for the moment

[Copilot]

Pull request overview

This pull request fixes Hot Reload for XAML when debugging with the mono runtime (specifically iOS and Android) in VS Code. The fix introduces a dual-channel approach where metadata deltas are applied through the debugger channel while updated type information is sent through the regular Hot Reload channel. The PR also includes memory optimizations using AsSpan() instead of ToArray() and eliminates unnecessary object allocations for empty arrays.

Changes:

• Extracted metadata update handler logic into a separate ApplyUpdatedTypes method in HotReloadAgent to allow independent invocation
• Modified validation logic to allow null metadata deltas when running with VSCode extension and mono debugger
• Implemented dual-channel approach: metadata deltas via IDE channel, updated types via regular channel when debugging with mono runtime
• Applied memory optimizations using AsSpan() for ImmutableArray<byte> conversions and early return for empty arrays

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Uno.UI.RemoteControl/HotReload/MetadataUpdater/HotReloadAgent.cs	Extracted ApplyUpdatedTypes method to enable separate invocation of metadata update handlers from delta application
src/Uno.UI.RemoteControl/HotReload/Messages/AssemblyDeltaReload.cs	Updated validation to conditionally allow null delta properties when running with VSCode extension
src/Uno.UI.RemoteControl/HotReload/ClientHotReloadProcessor.Agent.cs	Implemented conditional logic to skip delta application when debugging with mono runtime, while still applying updated types
src/Uno.UI.RemoteControl.Server.Processors/HotReload/ServerHotReloadProcessor.MetadataUpdate.cs	Refactored to send deltas through IDE channel and types through regular channel when debugging; applied memory optimizations with AsSpan()

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

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[Copilot]

@spouliot I've opened a new pull request, #22727, to work on those changes. Once the pull request is ready, I'll request review from you.

[unodevops]

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[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ spouliot
❌ Copilot
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[Copilot]

@spouliot I've opened a new pull request, #22768, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

src/Uno.UI.RemoteControl/HotReload/MetadataUpdater/HotReloadAgent.cs:241

• GetMetadataUpdateTypes(...) returns a non-null Type[], but it’s stored in a nullable local (Type[]? updatedTypes). This unnecessarily widens the nullability and makes it easier to accidentally introduce null handling later. Consider using a non-null local (var updatedTypes = ...) to match the method contract.

			Type[]? updatedTypes = GetMetadataUpdateTypes(deltas);

			handlerActions.ClearCache.ForEach(a => a(updatedTypes));
			handlerActions.UpdateApplication.ForEach(a => a(updatedTypes));

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[Copilot]

@spouliot I've opened a new pull request, #22771, to work on those changes. Once the pull request is ready, I'll request review from you.

[unodevops]

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22696/wasm-skia-net9/index.html

[unodevops]

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22696/wasm-skia-net9/index.html

[unodevops]

⚠️⚠️ The build 199540 has failed on Uno.UI - CI.