[Java.Interop] Decouple built-in proxies from ManagedPeer

[simonrozsival]

Summary

• register JavaProxyObject's native equals, hashCode, and toString callbacks with UTF-8 JniNativeMethod entries and [UnmanagedCallersOnly] function pointers
• remove the ManagedPeer.registerNativeMembers() Java initializers from JavaProxyObject and JavaProxyThrowable
• preserve the separate trimmable proxy's Java identity semantics
• add focused JVM coverage for managed equality, hash code, and string delegation

Context

This is the first implementation phase of #11727.

JavaProxyObject was using ManagedPeer only as a generic native-registration trampoline. It can register its three callbacks directly while retaining the existing non-trimmable/standalone behavior. Raw UCO function pointers avoid delegate marshaling, delegate lifetime management, and AOT suppressions. JNI jboolean is an unsigned 8-bit value, so the equals(Object) callback returns C# byte through a delegate* unmanaged<IntPtr, IntPtr, IntPtr, byte> function pointer; 0 and 1 map directly to JNI_FALSE and JNI_TRUE.

JavaProxyThrowable passed an empty registration string and has no managed native-registration callback, so its ManagedPeer call registered nothing and needs no replacement.

ManagedPeer itself remains for the existing JavaInterop1 JCW path. Removing that path and deleting ManagedPeer will happen separately after the supported consumers migrate to XAJavaInterop1.

Testing

• git diff --check
• Java.Interop JVM tests not run because the local dotnet/android SDK is not built

[Copilot]

Pull request overview

This PR is the first phase of decoupling Java.Interop’s built-in proxy types from ManagedPeer, by moving native registration for JavaProxyObject’s equals/hashCode/toString callbacks into managed code and removing the (now unnecessary) Java-side ManagedPeer.registerNativeMembers() initializers. It keeps the trimmable proxy’s identity semantics distinct, and adds focused JVM tests to validate delegation behavior.

Changes:

• Register JavaProxyObject native callbacks (equals, hashCode, toString) directly from the managed JavaProxyObject static constructor.
• Remove ManagedPeer.registerNativeMembers() static initializers from Java JavaProxyObject and JavaProxyThrowable.
• Add JVM test coverage verifying that JavaProxyObject’s Java method calls delegate to the wrapped managed object.

Show a summary per file

File	Description
src/java-runtime/java-trimmable/net/dot/jni/internal/JavaProxyObject.java	Clarifies trimmable proxy identity semantics vs the non-trimmable native-callback proxy behavior.
external/Java.Interop/tests/Java.Interop-Tests/Java.Interop/JniValueMarshalerContractTests.cs	Adds JVM coverage asserting proxy equals/hashCode/toString delegate to the managed wrapped value.
external/Java.Interop/src/Java.Interop/java/net/dot/jni/internal/JavaProxyThrowable.java	Removes no-op ManagedPeer.registerNativeMembers() initializer.
external/Java.Interop/src/Java.Interop/java/net/dot/jni/internal/JavaProxyObject.java	Removes ManagedPeer.registerNativeMembers() initializer; relies on managed-side native registration.
external/Java.Interop/src/Java.Interop/Java.Interop/JavaProxyObject.cs	Implements managed static-constructor native registration for equals/hashCode/toString.

Copilot's findings

• Files reviewed: 5/5 changed files
• Comments generated: 0

[simonrozsival]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

⚠️ Needs Changes (1 question to confirm)

Nice, focused change. Decoupling the built-in proxies from ManagedPeer and registering the three callbacks directly with blittable JniNativeMethod + [UnmanagedCallersOnly] function pointers is the right direction for AOT and avoids delegate marshaling/lifetime concerns.

Positive callouts:

• Returning byte (not bool) for the equals jboolean callback is actually more correct than the old delegate — default bool marshaling is a 4-byte Windows BOOL, whereas JNI jboolean is an unsigned 8-bit value. Good catch, and the 0/1 mapping is clean.
• Lazy registration under the existing CachedValues lock, before the first peer is allocated, is a tidy way to guarantee the natives are in place before Java can call them.
• Good JVM coverage in ProxyObjectMethodsDelegateToManagedValue exercising equality, hash code, and toString delegation to the wrapped managed value.
• The trimmable-copy comment is clearer than before.

To confirm / consider (see inline):

• ⚠️ The process-wide static bool nativeMethodsRegistered replaces a per-class-load Java static initializer. Please confirm no runtime-recreation / classloader-reload path can observe a stale true and skip registration.
• 💡 Duplicate JavaProxyObject type-name literal vs the existing JniTypeName const.

CI: checks are still pending (no failures yet); the PR notes JVM tests weren't run locally since the SDK wasn't built, so rely on pipeline results before merge.

Generated by Android PR Reviewer for #12152 · 118.5 AIC · ⌖ 13.1 AIC · ⊞ 6.8K
_{Comment /review to run again}

[github-actions]

🤖 ⚠️ JNI interop — nativeMethodsRegistered is a process-wide static flag, but the previous approach registered the callbacks from a Java static { ManagedPeer.registerNativeMembers(...) } initializer, which re-runs every time the class is loaded (e.g., under a fresh classloader / recreated runtime). With this flag, if a second JniRuntime is created in the same process — or the class is reloaded under a new classloader — registration is skipped and the new class's equals/hashCode/toString natives are left unregistered, leading to UnsatisfiedLinkError at runtime. On Android this is fine (single runtime per process), but please confirm no test/runtime-restart scenario reuses this stale flag. If reuse is possible, key the flag off the runtime instance rather than a plain bool.

(Rule: JNI native registration lifecycle)

[simonrozsival]

This is fine, we are only targeting Android.