[TrimmableTypeMap] Fix String and nullable array proxies by simonrozsival · Pull Request #12017 · dotnet/android

simonrozsival · 2026-07-08T07:51:50Z

Summary

Independent trimmable typemap array-proxy fixes extracted from #11822, so the NativeAOT default-flip PR can stay focused.

Emit built-in array proxy entries for System.String and boxed Nullable<T> value types, including Java.Interop GetType coverage for boxed nullable arrays.
Split array proxy rank defaults: primitive arrays keep _AndroidTrimmableTypeMapMaxArrayRank (3 under AOT), while reference-like arrays use _AndroidTrimmableTypeMapMaxReferenceArrayRank (1 under AOT) to avoid generating/compiling large rank-2/3 reference-array closures by default.
Fix nullable value type proxy codegen and make JavaPeerProxy's base constructor accessible to generated typemap proxy assemblies.

Testing

dotnet test tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests.csproj → 613 passed

Notes

Extracted from #11822. This does not change the NativeAOT default; it only fixes the opt-in trimmable typemap array behavior.

Issue references

Contributes to #10933 and #10793.

…pping GetTypes ("[Ljava/lang/String;") dropped the System.String array family (System.String[], JavaObjectArray<string>, JavaArray<string>) on NativeAOT. The runtime enumerates array element types via GetTypesForSimpleReference, which injects System.String for java/lang/String through GetBuiltInTypeForSimpleReference. But System.String is neither a scanned Java peer (EmitArrayEntriesForPeer) nor a primitive (EmitPrimitiveArrayEntries), so no array proxy was generated for it. On NativeAOT the array path relies on the pre-generated proxy map (TryGetArrayProxy), so the System.String element type yielded nothing. (CoreCLR fabricates the types dynamically, so it was fine.) Emit a System.String array proxy alongside the primitives in the _Java.Interop.TypeMap assembly, using the reference-array family (Primitive is null). The proxy map key "System.String, System.Runtime" matches TrimmableTypeMap.TryGetManagedTypeKey (typeof (string)). Fixes the System.String portion of Java.InteropTests.JniTypeManagerTests.GetType on the trimmable/NativeAOT path. Boxed-nullable element types (bool?/int?/... via java/lang/Boolean etc.) have the same shape and will be covered/verified by follow-up test coverage. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JniTypeManagerTests.GetType covered primitive keyword arrays ([Z..[D) and the System.String reference array ([Ljava/lang/String;), but not the boxed nullable counterparts. Add assertions for [Ljava/lang/Boolean;, [Ljava/lang/Byte;, [Ljava/lang/Character;, [Ljava/lang/Short;, [Ljava/lang/Integer;, [Ljava/lang/Long;, [Ljava/lang/Float;, [Ljava/lang/Double;. Each boxed reference maps to Nullable<T> (JniBuiltinSimpleReferenceToType / GetBuiltInTypeForSimpleReference), and the non-keyword array path yields JavaObjectArray<T?> and T?[] (no JavaArray<T>/JavaPrimitiveArray<T>). The expected types match the default ReflectionJniTypeManager behavior. These pass on the default typemap. On the trimmable typemap they exercise the same array-proxy gap just fixed for System.String; if the boxed element types lack pre-generated array proxies on NativeAOT they will fail, driving the follow-up implementation fix. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

GetTypes ("[Ljava/lang/Boolean;") and the other boxed value-type array signatures dropped the Nullable<T> array family (bool?[], JavaObjectArray<bool?>) on NativeAOT. Like System.String, Nullable<T> is a built-in reference mapping injected at runtime by GetBuiltInTypeForSimpleReference, so it is neither a scanned Java peer nor a primitive and had no pre-generated array proxy. Unlike String, the proxy map key is the tricky part: at runtime TryGetManagedTypeKey (typeof (bool?)) keyed on Type.FullName, whose type argument carries the full versioned assembly-qualified name (System.Nullable`1[[System.Boolean, System.Private.CoreLib, Version=...]]), which the generator can't stably reproduce. Normalize the generic key on both sides: * Runtime (BuildManagedTypeKey): build closed-generic keys from the open definition's FullName plus each type argument's normalized key (simple assembly name, no Version/Culture/PublicKeyToken), and treat Nullable<T> as a System.Runtime type. typeof (bool?) -> "System.Nullable`1[[System.Boolean, System.Runtime]], System.Runtime". * Generator (ModelBuilder): emit reference-array proxies for the eight Nullable<primitive> types that have a boxed java/lang mapping, keyed with the same normalized string. Normalizing (rather than emitting version-qualified duplicates) keeps a single canonical proxy per logical type. Fixes the boxed-nullable portion of JniTypeManagerTests.GetType on trimmable NativeAOT (added in the preceding test-coverage commit). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The trimmable typemap generates array-proxy types (JavaObjectArray<T>, T[], nested closures) up to a configurable rank so that array types can be resolved without Array.CreateInstance under NativeAOT. Emitting these uniformly at rank 3 caused a NativeAOT ILC type explosion: on an AppCompat app ILC compiled/preinitialized ~129,320 types and IlcCompile took 333s, which pushed the heaviest CI apps past the 30-min DefaultBuildTimeOut. Reference-type array proxies (scanned Java peers, System.String, boxed Nullable<T>) are now capped at a separate, lower rank (_AndroidTrimmableTypeMapMaxReferenceArrayRank, default 1 for NativeAOT) while primitive arrays keep the higher rank (default 3). Jagged reference arrays (Foo[][]) are rare, and each nesting level multiplies the JavaObjectArray<T> closure ILC must process, so this trims the bulk of the cost while preserving the common Foo[] and int[][][] cases. The anchor matrix (model.MaxArrayRank) stays uniform at max(primitive, reference) across all typemap assemblies so RootTypeMapAssemblyGenerator's rectangular [assembly][rank] sentinel layout is unchanged; only the emitted entries per rank differ. Measured on the same AppCompat NativeAOT app: ILC types 129,320 -> 22,673 (5.7x fewer) IlcCompile 333s -> 91s (3.65x faster) TypeMap DLLs 19.7MB -> 9.7MB (~2x smaller) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…ment The split-rank change capped all reference-type array proxies at rank 1, which regressed multidimensional string arrays: GetTypes("[[Ljava/lang/String;") no longer yielded System.String[][] / JavaObjectArray<JavaObjectArray<string>>. That expectation is baseline Java.Interop behavior (JniTypeManagerTests.GetType, since #517) that the managed/llvm-ir/reflection type maps all satisfy, so the trimmable type map must satisfy it too now that it is the default. System.String is a single, fixed built-in element type (injected at runtime by GetBuiltInTypeForSimpleReference), not part of the scanned-peer population that drives the NativeAOT ILC type explosion. Emit its array proxies up to the primitive maxArrayRank instead of maxReferenceArrayRank, exactly like the keyword primitives. The cost is negligible: on the AppCompat NativeAOT app ILC types went from 22,673 -> 22,717 (+44) and IlcCompile stayed ~60-90s (vs rank-3's 129,320 types / 333s). Scanned Java peers stay capped at maxReferenceArrayRank (1); boxed Nullable<T> built-ins likewise stay at rank 1 (no baseline coverage requires multidim boxed arrays). Also drop TryGetArrayProxy_ObjectLeaf_ReturnsAllRankTypes: its additionalRank:2 assertions expected Object[][] etc., which is exactly the reference-rank-2 case that split-rank intentionally no longer generates. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…lements Follow-up to promoting System.String: the boxed Nullable<T> value types (java/lang/Boolean, java/lang/Integer, ...) are built-in element mappings just like System.String and the keyword primitives — a small, fixed set that is not part of the scanned-peer population driving the NativeAOT ILC type explosion. Emit their array proxies up to maxArrayRank instead of maxReferenceArrayRank so all built-in element types are treated uniformly and multidimensional boxed arrays (int?[][], "[[Ljava/lang/Integer;") resolve. Only scanned Java peers remain capped at maxReferenceArrayRank (1). Cost stays negligible on the AppCompat NativeAOT app: ILC types 22,717 -> 23,101 (+384) and IlcCompile ~56s (vs rank-3's 129,320 types / 333s). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Generated typemap proxy types can derive directly from the non-generic JavaPeerProxy base when they need to represent interfaces or open generic definitions. Make the base constructor protected so those generated proxies can call it from typemap assemblies. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR improves the trimmable typemap’s array-proxy support by adding missing built-in proxies (notably System.String and boxed Nullable<T>), normalizing runtime array-proxy keys for closed generics, and introducing separate rank caps for reference vs primitive array proxies to reduce NativeAOT build-time/size costs.

Changes:

Generate array proxy entries/associations for System.String and boxed Nullable<T> (including updated unit tests validating metadata emission and signature decoding).
Add a separate reference-array rank property (MaxReferenceArrayRank / _AndroidTrimmableTypeMapMaxReferenceArrayRank) and plumb it through the MSBuild task + generator.
Normalize runtime managed-type keys for closed generics (e.g., Nullable<bool>) so runtime lookups match generator-emitted keys; relax JavaPeerProxy ctor visibility for generated proxy assemblies.

Show a summary per file

File	Description
Configuration.OperatingSystem.props	Adds a host-specific props file (appears to be a local artifact).
tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/TrimmableTypeMapTypeManagerTests.cs	Removes a reference-array proxy runtime test (coverage gap).
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TypeMapModelBuilderTests.cs	Expands generator tests for built-in String/Nullable proxies and split-rank behavior.
src/Xamarin.Android.Build.Tasks/Tasks/GenerateTrimmableTypeMap.cs	Adds `MaxReferenceArrayRank` task input and passes it to the generator.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets	Introduces default `_AndroidTrimmableTypeMapMaxReferenceArrayRank` and passes it to the task.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.CoreCLR.targets	Plumbs `MaxReferenceArrayRank` for the post-trim generator pass.
src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMap.cs	Normalizes managed-type keys for closed generics to match generated typemap keys.
src/Mono.Android/Java.Interop/JavaPeerProxy.cs	Makes the base constructor `protected` so generated typemap proxy assemblies can derive from it.
src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs	Adds `maxReferenceArrayRank` parameter and uses max rank for the root anchor matrix.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/TypeMapAssemblyGenerator.cs	Passes split-rank settings into `ModelBuilder`.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/ModelBuilder.cs	Emits built-in proxies for `System.String` and boxed `Nullable<T>`; caps scanned-peer arrays by reference rank.
external/Java.Interop/tests/Java.Interop-Tests/Java.Interop/JniTypeManagerTests.cs	Adds signature-to-type coverage for boxed `Nullable<T>` reference arrays.

Copilot's findings

Files reviewed: 12/12 changed files
Comments generated: 6

Restore object-leaf array proxy coverage for rank 1 and split the rank-2 reference-array assertions into an ignored test until higher-rank reference array proxy generation is revisited. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove the accidental host-specific Configuration.OperatingSystem.props file from the PR. Clarify that MaxReferenceArrayRank applies only to scanned Java peer arrays, while built-in primitives, System.String, and boxed Nullable<T> use MaxArrayRank. Drop the unused maxReferenceArrayRank parameter from EmitPrimitiveArrayEntries. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add _AndroidTrimmableTypeMapMaxReferenceArrayRank to the build property cache so changing the reference-array rank invalidates _GenerateTrimmableTypeMap just like the primitive/built-in rank does. Add a regression test for the property-cache invalidation and clarify the TypeMapAssemblyGenerator parameter docs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival · 2026-07-10T05:08:39Z

/review

github-actions · 2026-07-10T05:09:27Z

✅ Android PR Reviewer completed successfully!

github-actions

🤖 Review — ⚠️ Needs Changes (CI pending)

Solid, well-scoped change that splits the built-in element array rank (_AndroidTrimmableTypeMapMaxArrayRank) from the scanned-peer reference array rank (_AndroidTrimmableTypeMapMaxReferenceArrayRank), and adds explicit System.String and boxed Nullable<T> array proxies. I verified the key correctness path end-to-end:

Runtime/generator key symmetry ✅ — TrimmableTypeMap.BuildManagedTypeKey now emits the normalized, version-independent generic form (System.Nullable\1[[System.Boolean, System.Runtime]], System.Runtime) that exactly matches ModelBuilder.AssemblyQualify (TypeRefData). GetAssemblyNameForManagedTypeKeycorrectly normalizesNullable(T)(and its element) toSystem.Runtime`, matching the emitter.
Rank matrix ✅ — carrying Math.Max (maxArrayRank, maxReferenceArrayRank) into MaxArrayRank/the root generator keeps the __ArrayMapRank{N} anchor matrix rectangular while peers get only reference-rank entries. Covered by the new Build_ReferenceRankLowerThanPrimitiveRank_* tests.
Boxed mappings ✅ — sbyte? for java/lang/Byte (signed) is correct; the 8 boxed types are the right set.
Incremental build ✅ — new property is added to _PropertyCacheItems and both targets, with a regeneration test.
Test coverage ✅ — generator, full-pipeline round-trip, JniTypeManagerTests, and build tests all extended.

Findings

2 × 💡 suggestions (code consolidation + proxy-name convention) posted inline. No bugs or correctness issues found.

Notes

CI shows no combined status yet (pending). Per review policy this can't be marked LGTM until the Azure DevOps pipeline is green — please confirm CI passes before merge.
The removed maxArrayRank > 0 && guard before EmitPrimitiveArrayEntries is safe: the inner 1..maxArrayRank loops make it a no-op at rank 0.

Nice work — the extensive inline comments explaining the boxed-nullable/String rationale are genuinely helpful for future readers.

Generated by Android PR Reviewer for #12017 · 116.5 AIC · ⌖ 18.9 AIC · ⊞ 6.8K
_{Comment /review to run again}

github-actions · 2026-07-10T05:14:34Z

+		// signature. Like the primitives and System.String, these are a small fixed set of built-in
+		// element types (not the scanned-peer explosion), so they go up to maxArrayRank and keep
+		// multidim boxed arrays resolvable.
+		foreach (var nullablePrimitive in NullableArrayProxies) {


🤖 💡 Code organization — The three emission blocks in EmitPrimitiveArrayEntries (primitive, System.String, and Nullable<T>) repeat the same ~7 lines of boilerplate: build ArrayProxyData, model.ArrayProxyTypes.Add, build proxyReference, add the TypeMapAttributeData entry, and AddArrayProxyAssociations. Consider extracting a small local helper like EmitBuiltinArrayProxy (model, proxy) that takes the constructed ArrayProxyData and performs the add/entry/association steps. It would remove the duplication and ensure the three call sites stay in sync if the entry shape changes.

Rule: Code duplication / consolidation

github-actions · 2026-07-10T05:14:34Z

+		foreach (var nullablePrimitive in NullableArrayProxies) {
+			for (int rank = 1; rank <= maxArrayRank; rank++) {
+				var proxy = new ArrayProxyData {
+					TypeName = $"Nullable_{nullablePrimitive.Name}_ArrayProxy{rank}",


🤖 💡 Naming — The System.String block above uses the ManagedTypeNameToArrayProxyTypeName ("System.String", rank) helper to derive the proxy type name, while this Nullable<T> block hand-rolls $"Nullable_{nullablePrimitive.Name}_ArrayProxy{rank}" (and the primitive block hand-rolls $"Primitive_{...}_ArrayProxy{rank}"). Consider routing all three through the same helper (or documenting why the nullable names intentionally diverge) so the proxy-type-name convention has a single source of truth.

Rule: Consistency

simonrozsival and others added 8 commits July 8, 2026 09:50

Fix nullable value type codegen

63fd113

Copilot AI review requested due to automatic review settings July 8, 2026 07:51

simonrozsival requested a review from jonathanpeppers as a code owner July 8, 2026 07:51

Copilot started reviewing on behalf of simonrozsival July 8, 2026 07:52 View session

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simonrozsival and others added 2 commits July 8, 2026 09:58

simonrozsival added the trimmable-type-map label Jul 8, 2026

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[TrimmableTypeMap] Fix String and nullable array proxies#12017

[TrimmableTypeMap] Fix String and nullable array proxies#12017
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simonrozsival commented Jul 8, 2026

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