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[r8-obfuscation] Rewrite managed JNI metadata from R8 mappings - #12630
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Copilot review overview
🟡 Changes recommended
There are a couple of correctness issues in newly added code paths (custom-attribute prolog validation and Windows-safe in-place path detection) that should be addressed before merge.
Once you've addressed the issues Copilot identified, you can request another Copilot review.
Review tier: Lite
Findings: 3
New issues introduced by this change (3)
| Severity | Finding |
|---|---|
 | src/Xamarin.Android.Build.Tasks/Tasks/RewriteJniNamesForR8.cs — ❌ error — The in-place detection compares full paths using Ordinal, which can mis-detect the same… |
| src/Xamarin.Android.Build.Tasks/Utilities/JniRemapping/CustomAttributeStringRewriter.cs — ❌ error — Custom attribute blobs must start with the ECMA-335 0x0001 prolog; this currently only… |
| src/Xamarin.Android.Build.Tasks/Utilities/JniRemapping/JniRewritePlanner.cs — |
What changed in this PR
This PR adds the “layer 3” managed-side machinery needed to rewrite JNI-bearing managed metadata/IL strings based on an R8 mapping.txt, enabling opt-in R8 obfuscation while keeping managed ↔ Java/JNI references consistent.
Changes:
- Introduces a PE/metadata scan + rewrite plan (
JniRewritePlanner) and an assembly rewrite façade (JniAssemblyRewriter) to update Register/Jni*Signature attributes and relevantldstrstrings. - Adds an MSBuild task (
RewriteJniNamesForR8) that rewrites/copies assemblies (and adjacent PDBs) and emits a manifest of mapping entries consumed. - Adds XA4325/XA4326 resources + documentation, and extensive end-to-end tests for rewriting behavior and invariants (tokens, resources, debug directory, strong-name flag handling).
| File | Description |
|---|---|
| src/Xamarin.Android.Build.Tasks/Utilities/JniRemapping/JniRewritePlanner.cs | Scans metadata + IL to produce a deterministic rewrite plan and emits XA4326 warnings for unsafe legacy lookup rewrites. |
| src/Xamarin.Android.Build.Tasks/Utilities/JniRemapping/JniAssemblyRewriter.cs | Orchestrates planning + full assembly reconstruction using the existing rebuild substrate. |
| src/Xamarin.Android.Build.Tasks/Utilities/JniRemapping/CustomAttributeStringRewriter.cs | Low-level blob rewriter for fixed string args in custom attribute value blobs. |
| src/Xamarin.Android.Build.Tasks/Tasks/RewriteJniNamesForR8.cs | MSBuild task to apply rewrites across files, copy PDBs, and write a rewrite manifest; introduces XA4325 error surface. |
| src/Xamarin.Android.Build.Tasks/Properties/Resources.resx | Adds XA4325/XA4326 message resources. |
| src/Xamarin.Android.Build.Tasks/Properties/Resources.Designer.cs | Resource designer updates for XA4325/XA4326. |
| src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/JniRemapping/JniAssemblyRewriterTests.cs | End-to-end validation of metadata/IL rewrites and PE invariants. |
| src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/RewriteJniNamesForR8Tests.cs | Task-level tests for copy/rewrite behaviors and error handling. |
| Documentation/docs-mobile/TOC.yml | Adds TOC entries for XA4325/XA4326 docs. |
| Documentation/docs-mobile/messages/xa4325.md | Documents XA4325 error cases and guidance. |
| Documentation/docs-mobile/messages/xa4326.md | Documents XA4326 warning and guidance. |
| Documentation/docs-mobile/messages/index.md | Adds XA4325/XA4326 to the message index. |
Files not reviewed (1)
- src/Xamarin.Android.Build.Tasks/Properties/Resources.Designer.cs: Generated file
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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Replace the ad-hoc RJN0000/RJN0001 error codes and their hard-coded English strings with a single documented, localizable XA4325 product code. The task prefix stays "RJN" so unexpected exceptions keep reporting as XARJN7xxx, consistent with other task-specific prefixes; only the two explicit errors change. The user-visible detail is resource-backed as well: XA4325 is a general wrapper and the two specific failures live in XA4325_SourceDestinationCount and XA4325_AssemblyFailure, so no new English fragments are formatted into the message from code. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Associate legacy JNI member lookups with proven FindClass/Get*ID sequences, remove stale copied PDBs, and keep task outputs empty after rewrite failures. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Preserve managed constructor spellings, resolve cached static JNI class handles through proven FindClass assignments, warn on unsafe renamed lookup sources, and skip identity string rewrites. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Use platform-aware path identity for in-place rewrites, validate custom attribute prologs, and diagnose unsafe member-only mappings without polluting rewrite manifests or reverse scans. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Related to #12535
Depends on #12629
Layer 3 of 6 in the replacement stack for #12575.
This layer rewrites standard managed JNI metadata from R8 mappings. Trimmable typemap and FieldRVA handling follows in layer 4.