[TrimmableTypeMap] Runtime-only trimmable typemap support by simonrozsival · Pull Request #11090 · dotnet/android

simonrozsival · 2026-04-08T19:06:19Z

JNIEnv.TypemapManagedToJava uses managed JNI-name resolution from TrimmableTypeMap for the trimmable path
JNIEnvInit publishes the current JniRuntime before trimmable typemap initialization so managed JNI services and native registration work correctly
legacy TypeManager.GetJavaToManagedType is now explicitly unreachable in trimmable mode; lookups should flow through TrimmableTypeMapTypeManager
JavaMarshalValueManager + TrimmableTypeMap handle the remaining runtime peer creation/JNI-name resolution after the split and now fail fast if required proxy coverage is missing

Rebuild the remaining runtime-only portion of PR 11090 on top of main. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove the accidental fallback chain from TryGetJniName while preserving the cache. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Keep the trimmable peer path on TrimmableTypeMapTypeManager/JavaMarshalValueManager, make any legacy TypeManager lookup in trimmable mode fail fast, and tighten the proxy caches/state handling for parity with the existing activation flow. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Stop silently falling back when trimmable peer activation cannot resolve a generated JavaPeerProxy. In trimmable mode, missing proxy coverage should surface as an explicit runtime error so generator gaps are fixed at the source. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Collapse the trimmable managed-to-JNI lookup back to a single internal API by keeping TryGetJniNameForManagedType() and removing the duplicate TryGetJniName() entry point. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Reduce TrimmableTypeMap surface area by making purely local proxy helpers private and removing the unused TryCreatePeer() wrapper. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Rename GetProxyForPeer() to GetProxyForJavaObject() so the helper more clearly describes what it actually inspects and resolves. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival

🤖 AI Review Summary

Verdict: ⚠️ Needs Changes

Found 1 issue, and the PR is not mergeable yet because the required dotnet-android checks are still pending.

⚠️ Error handling: JavaMarshalValueManager.CreatePeer() now bypasses the base JniValueManager guards for disposed managers and invalid JniObjectReference values, so the trimmable path can throw the new NotSupportedException where the inherited contract would return null or raise ObjectDisposedException (src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs:510).

👍 Nice cleanup overall: the runtime-only split is much clearer now, especially the removal of the legacy TypeManager redirect and the narrower TrimmableTypeMap surface.

Review generated by android-reviewer from review guidelines.

src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs

Preserve the inherited JniValueManager.CreatePeer() preconditions for disposed managers and invalid JNI references before the trimmable fail-fast proxy check. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Adds runtime-side support for the trimmable typemap path in Mono.Android, shifting managed↔JNI name/type resolution and peer creation away from legacy typemap codepaths and ensuring JniRuntime is published early enough for trimmable initialization.

Changes:

Route JNIEnv.TypemapManagedToJava to managed TrimmableTypeMap when RuntimeFeature.TrimmableTypeMap is enabled.
Publish the current JniRuntime earlier in JNIEnvInit and initialize TrimmableTypeMap post-runtime creation.
Make legacy TypeManager.GetJavaToManagedTypeCore explicitly unreachable in trimmable mode and centralize peer creation via TrimmableTypeMap.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs	Adds caches and new logic for resolving proxies/JNI names and creating peers for Java objects in trimmable mode.
src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs	Switches peer creation in trimmable mode to `TrimmableTypeMap.CreatePeer` and fails fast when proxy coverage is missing.
src/Mono.Android/Java.Interop/TypeManager.cs	Throws an `UnreachableException` if legacy java→managed lookup is used while trimmable typemap is enabled.
src/Mono.Android/Android.Runtime/JNIEnvInit.cs	Sets the current `JniRuntime` earlier and again after constructing `AndroidRuntime`, before typemap initialization.
src/Mono.Android/Android.Runtime/JNIEnv.cs	Uses managed trimmable typemap resolution for managed→Java type mapping when enabled.

src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs

Copilot · 2026-04-10T11:34:53Z

src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs

+					var cached = _peerProxyCache.GetOrAdd (className, static (name, self) => {
+						if (!self._typeMap.TryGetValue (name, out var mappedType)) {
+							return null;
+						}
+
+						return mappedType.GetCustomAttribute<JavaPeerProxy> (inherit: false);
+					}, this);
+


_peerProxyCache.GetOrAdd can return null when the Java type isn't present in _typeMap, but ConcurrentDictionary cannot store null values. This will throw during hierarchy walking for unknown Java types. Consider caching only successful lookups, or use a non-null sentinel/wrapper to represent a miss.

Suggested change

var cached = _peerProxyCache.GetOrAdd (className, static (name, self) => {

if (!self._typeMap.TryGetValue (name, out var mappedType)) {

return null;

}

return mappedType.GetCustomAttribute<JavaPeerProxy> (inherit: false);

}, this);

JavaPeerProxy? cached = null;

if (!_peerProxyCache.TryGetValue (className, out cached)) {

if (_typeMap.TryGetValue (className, out var mappedType)) {

cached = mappedType.GetCustomAttribute<JavaPeerProxy> (inherit: false);

if (cached != null) {

cached = _peerProxyCache.GetOrAdd (className, cached);

}

}

}

Copilot · 2026-04-10T11:34:53Z

src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs

+			if (proxy is not null && TryGetJniNameForManagedType (targetType, out var targetJniName)) {
+				var selfRef = new JniObjectReference (handle);
+				var objClass = JniEnvironment.Types.GetObjectClass (selfRef);
+				var targetClass = JniEnvironment.Types.FindClass (targetJniName);
+				try {
+					if (!JniEnvironment.Types.IsAssignableFrom (objClass, targetClass)) {
+						proxy = null;
+					}
+				} finally {
+					JniObjectReference.Dispose (ref objClass);
+					JniObjectReference.Dispose (ref targetClass);
+				}


In CreatePeer(), objClass is acquired before FindClass(). If FindClass(targetJniName) throws (e.g., class missing), objClass won't be disposed because the try/finally is entered only after both locals are initialized. Refactor so objClass is always disposed (initialize targetClass to default and assign within the try).

Copilot · 2026-04-10T11:34:53Z

src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs

+			var targetName = targetType?.AssemblyQualifiedName ?? "<null>";
+			var javaType = JniEnvironment.Types.GetJniTypeNameFromInstance (reference);
+			throw new NotSupportedException (
+				$"No generated {nameof (JavaPeerProxy)} was found for Java type '{javaType}' " +
+				$"with targetType '{targetName}' while {nameof (RuntimeFeature.TrimmableTypeMap)} is enabled. " +
+				$"This indicates a missing trimmable typemap proxy or association and should be fixed in the generator.");
 		}


When trimmable typemap peer creation fails, this code throws without disposing reference using the provided transfer option. That can leak JNI references on error paths. Dispose reference (or otherwise ensure ownership is released) before throwing.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival

🤖 AI Review Summary

Verdict: ⚠️ Needs Changes

Found 1 issue, and the internal dotnet-android pipeline is also currently red due to a CS0234 compile error in JavaMarshalValueManager.cs.

❌ API design: TryGetTargetType() now throws for generated typemap alias entries, so a normal Java→managed lookup on an alias such as jni/name[1] will fail before the #10788 follow-up lands (src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs:81).

👍 The split between proxy resolution in TrimmableTypeMap and peer activation in JavaMarshalValueManager is a nice cleanup.

Review generated by android-reviewer from review guidelines.

simonrozsival · 2026-04-10T14:20:14Z

src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs

+		if (proxy is null) {
+			// Alias typemap entries (for example "jni/name[1]") are not implemented yet.
+			// Support for them will be added in a follow-up for https://github.com/dotnet/android/issues/10788.
+			throw new NotImplementedException (


🤖 ❌ API design — TryGetTargetType() is part of the probe path used during Java→managed resolution, but this branch now throws NotImplementedException for alias slots like jni/name[1]. Since those aliases are emitted by the typemap generator, a normal lookup will now crash before the follow-up PR lands. Can we keep alias entries non-fatal here (for example, return false until #10788 is implemented) instead of throwing?

Rule: API design

Thanks — this is intentional for now. We are still in the middle of the trimmable typemap rollout, and alias handling is explicitly being deferred to the follow-up in #10788. I would prefer to keep that work out of this PR rather than expand the scope further.

This was referenced Apr 8, 2026

[TrimmableTypeMap] Test plumbing and CI lane for Mono.Android.NET-Tests #11091

Draft

Enable trimmable typemap for Mono.Android.NET-Tests #11087

Closed

simonrozsival added trimmable-type-map copilot `copilot-cli` or other AIs were used to author this labels Apr 9, 2026

simonrozsival force-pushed the dev/simonrozsival/trimmable-uco-inline branch from b676200 to c19872c Compare April 9, 2026 15:58

[TrimmableTypeMap] Runtime trimmable typemap support

3a8d509

Rebuild the remaining runtime-only portion of PR 11090 on top of main. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the dev/simonrozsival/trimmable-runtime-fixes branch from d5aefaa to 3a8d509 Compare April 10, 2026 09:49

simonrozsival changed the title ~~[TrimmableTypeMap] Runtime trimmable typemap support~~ [TrimmableTypeMap] Runtime-only trimmable typemap support Apr 10, 2026

simonrozsival changed the base branch from dev/simonrozsival/trimmable-uco-inline to main April 10, 2026 09:49

simonrozsival and others added 6 commits April 10, 2026 11:53

[TrimmableTypeMap] Keep cached proxy-only JNI lookup

d4152df

Remove the accidental fallback chain from TryGetJniName while preserving the cache. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

[TrimmableTypeMap] Prune internal peer helpers

aa33e56

Reduce TrimmableTypeMap surface area by making purely local proxy helpers private and removing the unused TryCreatePeer() wrapper. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

[TrimmableTypeMap] Clarify Java object proxy lookup

47089ad

Rename GetProxyForPeer() to GetProxyForJavaObject() so the helper more clearly describes what it actually inspects and resolves. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival commented Apr 10, 2026

View reviewed changes

src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs Show resolved Hide resolved

[TrimmableTypeMap] Restore CreatePeer guard semantics

c4b567c

Preserve the inherited JniValueManager.CreatePeer() preconditions for disposed managers and invalid JNI references before the trimmable fail-fast proxy check. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival marked this pull request as ready for review April 10, 2026 11:27

simonrozsival requested a review from jonathanpeppers as a code owner April 10, 2026 11:27

Copilot AI review requested due to automatic review settings April 10, 2026 11:27

Copilot started reviewing on behalf of simonrozsival April 10, 2026 11:28 View session

Copilot AI reviewed Apr 10, 2026

View reviewed changes

simonrozsival and others added 8 commits April 10, 2026 14:10

Fix trimmable typemap review issues

9c5672b

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Refine trimmable typemap cleanup

4a68393

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Inline sentinel cache handling

2897a08

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Reuse managed proxy lookup

7a7c186

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Rename typemap target lookup

48102b6

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Extract Java proxy cache helper

530b2b2

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Separate proxy lookup from activation

0bad300

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Refactor Java proxy resolution

f626700

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival and others added 3 commits April 10, 2026 15:16

Inline typemap cache resolution

79ddbfb

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Tidy typemap helper flow

cb32b91

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Fail fast on typemap aliases

af4a2df

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival commented Apr 10, 2026

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[TrimmableTypeMap] Runtime-only trimmable typemap support#11090

[TrimmableTypeMap] Runtime-only trimmable typemap support#11090
simonrozsival wants to merge 19 commits intomainfrom
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simonrozsival commented Apr 8, 2026 •

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-					var cached = _peerProxyCache.GetOrAdd (className, static (name, self) => {
-						if (!self._typeMap.TryGetValue (name, out var mappedType)) {
-							return null;
-						}
-						return mappedType.GetCustomAttribute<JavaPeerProxy> (inherit: false);
-					}, this);
+					JavaPeerProxy? cached = null;
+					if (!_peerProxyCache.TryGetValue (className, out cached)) {
+						if (_typeMap.TryGetValue (className, out var mappedType)) {
+							cached = mappedType.GetCustomAttribute<JavaPeerProxy> (inherit: false);
+							if (cached != null) {
+								cached = _peerProxyCache.GetOrAdd (className, cached);
+							}
+						}
+					}

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simonrozsival commented Apr 8, 2026 •

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