Add MetadataUpdateDeletedAttribute

[steveisok]

This attribute is intended to be emitted only by Roslyn. The plan is for it to be used by reflection as a filter to "remove" types and members that have been deleted during a hot reload session.

Implements #118903

[Copilot]

Pull Request Overview

This PR introduces a new MetadataUpdateDeletedAttribute that will be emitted by Roslyn to mark types and members as deleted during hot reload sessions. This attribute is designed to be used by reflection as a filter to "remove" types and members that have been deleted.

Key changes:

• Adds the new MetadataUpdateDeletedAttribute class to the runtime
• Updates reference assemblies to include the new attribute
• Includes various compatibility suppressions that appear unrelated to the main change

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/libraries/System.Runtime.Loader/ref/System.Runtime.Loader.cs	Adds the reference definition of MetadataUpdateDeletedAttribute
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/MetadataUpdateDeletedAttribute.cs	Implements the actual MetadataUpdateDeletedAttribute class with documentation
src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems	Adds the new source file to the build
src/libraries/System.Collections.Specialized/src/CompatibilitySuppressions.xml	Removes a comment line (unrelated to main change)
src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml	Adds various compatibility suppressions (unrelated to main change)
src/coreclr/System.Private.CoreLib/CompatibilitySuppressions.xml	Adds compatibility suppressions for CoreCLR (unrelated to main change)

[steveisok]

Even though the API was approved, this change should not be merged until dotnet/roslyn#80125 goes into Roslyn.

[jkotas]

Even though the API was approved, this change should not be merged until dotnet/roslyn#80125 goes into Roslyn.

I do not think this PR needs to wait for that. The support for this attribute is in Roslyn already.

Is the actual implementation of the filtering and tests coming to this PR?

[steveisok]

Is the actual implementation of the filtering and tests coming to this PR?

I can - would prefer that actually. Wasn't sure if the preference was separate so started this way.

[jkotas]

Yes, we prefer to have the API exposed, implemented and tested all in one PR.

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[tmat]

@jkotas @steveisok I pushed a commit addressing Jan's feedback.

A few hurdles:

• I need to update Roslyn version that the tool that generates the deltas is using.
• Roslyn currently doesn't support any changes to interface or virtual methods, so we can't easily test deleting overrides. I included them in the tests anyways so that it's easy to enable in future.
• I was not able to build the runtime on my devbox, so wasn't able to actually run the tests and validate the impl. The linker hangs :(

[jkotas]

I was not able to build the runtime on my devbox, so wasn't able to actually run the tests and validate the impl. The linker hangs :(

Yes, it is https://developercommunity.visualstudio.com/t/C-compiling-hangs-building-checked-bui/10974056 . It would help if you can comment on it to motivate folks to get it fixed faster.

It can be worked around by using debug build of the runtime (-rc debug) that is super slow for running libraries tests.

[tmat]

Updated HotReload utils to new Roslyn version: dotnet/hotreload-utils#619

[tmat]

HotReloadUtils update: [release/10.0] Update dependencies from dotnet/hotreload-utils by dotnet-maestro[bot] · Pull Reques…

[steveisok]

@jkotas can you give this another pass? I think we're down to mono reflection quirks.

[jkotas]

Looks good to me ... once all tests are green.