[r8-obfuscation] Rewrite trimmable typemap JNI metadata

[simonrozsival]

Related to #12535

Depends on #12630

Layer 4 of 6 in the replacement stack for PR #12575. Build-pipeline activation follows in layers 5 and 6.

[simonrozsival]

/azp run

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[simonrozsival]

/azp run

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[simonrozsival]

/azp run

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[simonrozsival]

/azp run

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/azp run

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[simonrozsival]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

Generated by Android PR Reviewer for #12631

[Copilot]

Copilot review overview

🟡 Changes recommended

The new custom-attribute string-array rewriter reads the array length using host endianness and doesn’t validate the required attribute prolog, which can misparse blobs and should be fixed before merge.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review tier: Lite
Findings: 1 · 1

New issues introduced by this change (2)

Severity	Finding
	src/​Xamarin.Android.Build.Tasks/​Utilities/​JniRemapping/​CustomAttributeStringRewriter.cs — ❌ The custom attribute string-array rewriter doesn’t validate the 0x0001 prolog and reads the array…
	tests/​Microsoft.Android.Sdk.TrimmableTypeMap.Tests/​Generator/​TypeMapAssemblyGeneratorTests.cs — 💡 ReadInlineMethodTokens is now used for ldsflda (field) tokens as well as method tokens, so…

What changed in this PR

This PR extends the R8 JNI name remapping pipeline to cover trimmable typemap metadata that is stored outside simple ldstr strings, so managed JNI metadata stays consistent with R8 mappings when obfuscation is enabled.

Changes:

• Add support for rewriting FieldRVA-backed null-terminated UTF-8 JNI data (method names and descriptors) using R8 mappings, with conflict detection when shared data would require incompatible rewrites.
• Extend custom-attribute rewriting to cover TypeMapAttribute<T> keys and JavaPeerAliasesAttribute string arrays.
• Update the trimmable typemap generator to deduplicate signatures but not method names, since R8 member renames are owner-specific.

File	Description
tests/​Microsoft.Android.Sdk.TrimmableTypeMap.Tests/​Generator/​TypeMapAssemblyGeneratorTests.cs	Updates generator tests to reflect signature-only deduplication and adds field-token assertions.
src/​Xamarin.Android.Build.Tasks/​Utilities/​MetadataExtensions.cs	Improves GetCustomAttributeFullName handling for generic TypeSpecification parents (TypeRef/TypeDef).
src/​Xamarin.Android.Build.Tasks/​Utilities/​JniRemapping/​JniRewritePlanner.cs	Plans rewrites for FieldRVA UTF-8 data, TypeMapAttribute keys, and JavaPeerAliasesAttribute arrays; adds JavaPeerProxy owner resolution via .ctor IL.
src/​Xamarin.Android.Build.Tasks/​Utilities/​JniRemapping/​JniAssemblyRewriter.cs	Plumbs FieldRvaTable into rewrite planning and reverse-scan validation.
src/​Xamarin.Android.Build.Tasks/​Utilities/​JniRemapping/​CustomAttributeStringRewriter.cs	Documents expanded scope and adds a helper to rewrite string-array fixed arguments.
src/​Xamarin.Android.Build.Tasks/​Tests/​Xamarin.Android.Build.Tests/​Utilities/​JniRemapping/​JniAssemblyRewriterTests.cs	Adds coverage for typemap key/alias rewriting and FieldRVA UTF-8 rewrite behavior and failure modes.
src/​Microsoft.Android.Sdk.TrimmableTypeMap/​Generator/​TypeMapAssemblyEmitter.cs	Filters registrations to those with wrappers and prepares UTF-8 fields as (shared signatures, unique method names).
src/​Microsoft.Android.Sdk.TrimmableTypeMap/​Generator/​PEAssemblyBuilder.cs	Splits UTF-8 FieldRVA preparation into shared vs unique caches and exposes GetUniqueUtf8Field.

[github-actions]

Reviewed the JNI metadata rewrite, owner-specific FieldRVA allocation, reverse-scan behavior, alias rewriting, wrapper reuse, and the accompanying regression coverage. I found no actionable issues in the changed lines.

CI build #1580573 is still in progress; the currently visible checks show no failures, so this is not yet a green-build determination.

Generated by Android PR Reviewer for #12631 · gpt56 · 322.2 AIC · ⌖ 12.9 AIC · ⊞ 25.7K
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