[Mono.Android] Release transferred JNI inputs on exceptions - #13015

Refs #13010 (finding 2). Independent, non-stacked fix; this does not close the investigation tracker.

Transferred JNI inputs leaked when peer construction, lookup, Throwable metadata extraction, or generated Java.Interop activation threw before success-path JNIEnv.DeleteRef(). Release the original input in finally at boundaries that retain its ownership while nested construction receives Copy/CopyAndDoNotRegister.

Java.Lang.Throwable reads message, cause, and stack before SetHandle(). A new borrowed-only protected Java.Interop.JavaException initialization overload releases a typed transferred input only on initialization failure; success leaves normal transfer consumption to SetHandle(). Existing constructors retain their behavior; Java.Interop has no Android ownership dependency. Wrapper-owned copied GREFs remain separate from the input.

Generated Java.Interop leaf/invoker activation uses try/finally IL with the return outside the EH region. Xamarin-style proxies still delegate transfer to their IntPtr constructors, without a second cleanup owner. Unsupported inherited class-constructor activation stays null; supported inherited-interface invokers are tested. No registration-order, finalizer suppression, control-block, bridge-synchronization, or Throwable DoNotRegister policy changes.

Regression evidence

Restoring the original unsafe Object/Throwable boundaries and post-constructor-only generated cleanup, rebuilding the SDK, and cleaning/rebuilding the APK produced 20 failures / 26 passes in the 46-case matrix. Each failure expected one deletion of the original transferred handle and observed zero. Covered failures: local/global construction, unmapped lookup, GetObject/direct leaf/invoker activation, independent message/cause/first-stack/second-stack extraction.

With fixes restored, 46 regressions + 5 existing invoker tests passed twice on CoreCLR/trimmable arm64 and all 51 passed on Release NativeAOT/trimmable arm64, zero ignored. Coverage includes success, existing-peer return, incompatible/null result, borrowing, local/global transfer, DoNotRegister, and separately disposed partial-wrapper copies. The test-only forwarding observer checks exact handle/type/local-thread deletion, delegates native operations/counts/logging, leaves the bridge's cached manager unchanged, and restores the runtime manager in finally. Its preserved private-setter access executed under NativeAOT. Source-object copied GREFs are independently tracked and asserted disposed.

Generator regressions originally found zero EH regions; fixed emitted-shape and related coverage passed 19/19. The non-Android JVM fixture, its Java fixture, and unused TestJVM observation hook were removed at user request in 3c230eb. Android and generator regressions remain unchanged. Historical JVM results are not claimed as retained coverage.

Local validation

Commands use this branch's own source-built SDK. Validation-only RuntimeFrameworkVersion=10.0.0 worked around unavailable host reference pack 10.0.13; no product pins changed and Android app builds did not use that override.

• ./dotnet-local.sh build build-tools/scripts/Prepare.proj -t:Prepare -p:RuntimeFrameworkVersion=10.0.0 — passed; default preparation initially failed on missing Microsoft.NETCore.App.Ref 10.0.13.
• RuntimeFrameworkVersion=10.0.0 DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh build src/Mono.Android/Mono.Android.csproj -p:AndroidApiLevel=37.1 -p:AndroidPlatformId=37.1 -p:AndroidFrameworkVersion=v17.1 -v minimal — passed, 39 existing warnings, zero errors.
• RuntimeFrameworkVersion=10.0.0 DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh build src/Mono.Android/Mono.Android.csproj -p:AndroidApiLevel=37.2 -p:AndroidPlatformId=37.2 -p:AndroidFrameworkVersion=v17.2 -v minimal — passed, 39 existing warnings, zero errors.
• RuntimeFrameworkVersion=10.0.0 DOTNET_ROLL_FORWARD=Major make all — passed, including workload configuration; repeated after restoring all fixes.
• DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh test src/Microsoft.Android.Build.Tasks/Tests/Microsoft.Android.Build.Tasks.Tests/Microsoft.Android.Build.Tasks.Tests.csproj -p:RuntimeFrameworkVersion=10.0.0 --filter 'FullyQualifiedName~TransferredReferenceActivationTests|FullyQualifiedName~GenerateTrimmableTypeMapTests' -v minimal — 19 passed, zero failed/skipped.

CoreCLR build/install:
ANDROID_SERIAL=emulator-5556 DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh build -t:Install -c Debug tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj -p:AndroidTypeMapImplementation=trimmable -p:AdbTarget='-s emulator-5556' -p:IncludeCategories=TransferredReferences%3BInvokerActivation — passed, zero warnings/errors.

From tests/Mono.Android-Tests/Mono.Android-Tests:
ANDROID_SERIAL=emulator-5556 DOTNET_ROLL_FORWARD=Major ../../../dotnet-local.sh test Mono.Android.NET-Tests.csproj --no-build -c Debug -p:AndroidTypeMapImplementation=trimmable -p:AdbTarget='-s emulator-5556' -p:IncludeCategories=TransferredReferences%3BInvokerActivation --device emulator-5556 --report-trx --results-directory ../../../bin/TestDebug/TestResults — 51 selected/executed/passed, zero failed/ignored, twice. Original-behavior negative control used only category TransferredReferences: 20 failed / 26 passed.

NativeAOT build/install:
ANDROID_SERIAL=emulator-5556 DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh build -t:Install -c Release tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj -p:PublishAot=true -p:RuntimeIdentifier=android-arm64 -p:AndroidTypeMapImplementation=trimmable -p:AdbTarget='-s emulator-5556' -p:IncludeCategories=TransferredReferences%3BInvokerActivation — passed, 13 experimental/trim/AOT warnings, zero errors; verified native application .so payload.

From the same test-project directory:
ANDROID_SERIAL=emulator-5556 DOTNET_ROLL_FORWARD=Major ../../../dotnet-local.sh test Mono.Android.NET-Tests.csproj --no-build -c Release -p:PublishAot=true -p:RuntimeIdentifier=android-arm64 -p:AndroidTypeMapImplementation=trimmable -p:AdbTarget='-s emulator-5556' -p:IncludeCategories=TransferredReferences%3BInvokerActivation --device emulator-5556 --report-trx --results-directory ../../../bin/TestRelease/TestResults — 51 selected/executed/passed, zero failed/ignored.

After removing non-Android scaffolding:
DOTNET_ROLL_FORWARD=Major ./dotnet-local.sh build tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj -c Debug -p:AndroidTypeMapImplementation=trimmable -p:IncludeCategories=TransferredReferences%3BInvokerActivation -v minimal — passed, zero warnings/errors. Device tests were not rerun for this removal-only follow-up; no Android fixture or product behavior changed.

git diff --check — passed. Device runs used a dedicated API35 arm64 emulator, now shut down.

Remaining uncertainty and scope

Four initial VM-wide GREF-count assertions observed +1, including borrowed cases. These remain unattributed, not dismissed as unrelated. Final handle-level observer runs had no outstanding observed GREF acquisitions and separately checked peer copies. This exceptional-path defect is not established as the cause of the intermittent successful-activation leak check.

MonoVM, other ABIs, and full suites were not run. Unsupported inherited class activation remains unchanged.

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