[TrimmableTypeMap] Add trimmable [Export] and [ExportField] callback support

[simonrozsival]

Summary

Add UCO (UnmanagedCallersOnly) wrapper codegen for [Export] methods and [ExportField] fields in the trimmable typemap pipeline, plus test pruning and stabilization for the CoreCLRTrimmable test lane.

Part of #10788

Changes

Export support

• Scanner: Detect [Export] and [ExportField] attributes, resolve JNI signatures for non-primitive Java-bound parameter types, collect Java access modifiers and throws clauses
• Model: MarshalMethodInfo.IsExport / JavaAccess / ThrownNames / SuperArgumentsString carry all export metadata
• JCW Java codegen: Generate Java native methods with correct access modifiers and throws clauses for [Export] methods; generate Java field declarations for [ExportField]
• UCO wrappers + RegisterNatives: Export methods get the same UCO wrapper + JNI native registration as [Register] methods
• Mono.Android.Export exclusion: Exclude Mono.Android.Export from trimmable packages (its dynamic DynamicMethod codegen is incompatible with AOT/trimming)

Test stabilization

• Prune and reorganize CoreCLRTrimmable test exclusions
• Propagate deferred registerNatives to base classes
• Fix test plumbing for trimmable test lane

[Copilot]

Pull request overview

This PR extends the TrimmableTypeMap pipeline to support legacy [Export] / [ExportField] callbacks (including UCO wrapper + RegisterNatives generation and richer signature/metadata scanning), and adjusts test/build plumbing to stabilize the CoreCLRTrimmable test lane (including excluding Mono.Android.Export from app packaging on the trimmable path).

Changes:

• Add scanner + model support for [Export] / [ExportField], including signature resolution for Java-bound types and [ExportParameter] legacy marshalling shapes.
• Add generator support for direct-dispatch UCO wrappers for [Export] (new ExportMethodDispatchEmitter) and align typemap/manifest generation behavior.
• Stabilize CI/test lanes: introduce CoreCLRTrimmable flavor + categories, defer registerNatives up base class chains, and ensure Mono.Android.Export isn’t packaged on the trimmable path.

Reviewed changes

Copilot reviewed 31 out of 31 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaPeerScanner.cs	Detect/export [Export] metadata, compute JNI signatures with legacy marshalling shapes, and record precise managed type/assembly info.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/ExportMethodDispatchEmitter.cs	New emitter that generates UCO wrappers which dispatch directly to managed [Export] targets (avoids legacy dynamic callback generation).
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/TypeMapAssemblyEmitter.cs	Integrate export dispatch emitter, refactor RegisterNatives emission, and adjust proxy/UCO emission flow.
src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs	Manifest rooting rewrite + propagation of deferred registration flags to base classes; pass prepared manifest through generation.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets	Mark Mono.Android.Export references with AndroidSkipAddToPackage=true for trimmable typemap builds.
src/Xamarin.Android.Build.Tasks/Tasks/GenerateNativeApplicationConfigSources.cs	Skip assemblies marked AndroidSkipAddToPackage when generating native app config sources.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/*	New/updated fixtures and assertions covering export scanning, export dispatch generation, manifest rewriting, and instrumentation defaults.
tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj	Add CoreCLRTrimmable configuration defaults (runtime selection, categories, constants).
build-tools/automation/yaml-templates/stage-package-tests.yaml	Add CoreCLRTrimmable instrumentation lane and adjust CoreCLR lane args.

[Copilot]

_baseCtorRef is assigned but never used, and the encoded .ctor signature here doesn’t match JavaPeerProxy<T> (it encodes two System.Type parameters instead of string + Type). This should be removed to avoid dead/incorrect metadata and to prevent future accidental use of a wrong member reference.

Suggested change

	_baseCtorRef = _pe.AddMemberRef (_javaPeerProxyRef, ".ctor",
	sig => sig.MethodSignature (isInstanceMethod: true).Parameters (2,
	rt => rt.Void (),
	p => {
	p.AddParameter ().Type ().Type (_systemTypeRef, false);
	p.AddParameter ().Type ().Type (_systemTypeRef, false);
	}));

[simonrozsival]

🤖 Code Review — PR #11123

Verdict: ⚠️ Needs Changes (1 warning, 2 suggestions; CI still pending)

Summary

Solid implementation of [Export]/[ExportField] for the trimmable typemap pipeline. The static UCO dispatch via [UnmanagedCallersOnly] + RegisterNatives is correct, the IL generation handles all primitive/object/array/stream/XML marshalling shapes, and the test coverage is thorough (162 new test assertions across scanner, model builder, assembly generator, JCW codegen, and build integration). The Mono.Android.Export.dll exclusion from the packaged APK is properly wired.

Positive callouts

• ExportMethodDispatchEmitterContext factory — single-allocation, reused for the entire emit pass. Clean separation from the parent emitter.
• ExportParameterKind support — properly resolves InputStream, OutputStream, XmlPullParser, XmlResourceParser marshalling in both directions (JNI→managed and managed→JNI return).
• Array copy-back with null guards — the Brfalse_s skip pattern correctly avoids null-array copy-back crashes.
• Cross-assembly type resolution — TypeRefSignatureTypeProvider + MetadataTypeNameResolver properly chase ResolutionScope to the correct assembly reference, and the test Generate_ExportProxy_UsesExactCrossAssemblyTypeReferences validates it end-to-end.

CI (Xamarin.Android-PR) is still pending — review is based on code analysis only.