Fix: keep all Android ABIs in jniLibs for Noir React Native by bl0nnn · Pull Request #726 · zkmopro/mopro

bl0nnn · 2026-08-29T23:48:52Z

Summary

Current implementation of android Noir multi target invocation for react native (react_native_noir.rs) clears the jnilibs directory at each iteration leaving just the last android built lib inside.

This happens because uniffi-bindgen-react-native build android wipes jniLibs on every invocation by design since ubrn treats a build as the entire set of ABIs and Noir needs one invocation per arch.

Gradle still lists every requested ABI so the missing .so error pops up during app installation:

> Task :mopro-ffi:buildCMakeDebug[arm64-v8a] FAILED
C/C++: ninja: error: '../../../../src/main/jniLibs/arm64-v8a/libmopro_example_app.so', needed by '../../../../build/intermediates/cxx/Debug/3n733m4t/obj/arm64-v8a/libmopro-ffi.so', missing and no known rule to make it

This error shows missing arm64-v8a lib even tough mopro build ran with --architectures aarch64-linux-android x86_64-linux-android

Fix

To fix this one mopro build has to generate a single jniLibs tree instead of one for each iteration and then copy that to the jnilibs directory.

Steps:

Wipe once the old jnilibs tree android/src/main/jniLibs
Let ubrn run with the --no-jniLibs to suppress the copying of the Rust library into the JNI library directories
copy the lib for each requested android triple from target/<triple>/<profile>/lib<crate>.so → jniLibs/<abi>/

note: the mapping triple -> ABI was already managed by a private function in the mopro-ffi's react_native.rs file, I made that public and reused it.

Summary by CodeRabbit

Bug Fixes
- Improved React Native Android builds by validating supported architectures before packaging.
- Reliably packages native libraries in the correct ABI-specific locations.
- Improved build consistency across architectures and build modes.
- Reduced stale or misplaced native binaries during repeated builds.
- Improved handling of architecture-specific build outputs for dependable Android integration.
- Prevented unrequested WASM scaffolding from remaining in React Native bindings.

coderabbitai · 2026-08-29T23:49:10Z

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Reviewing files that changed from the base of the PR and between 23640e9 and 7e33fc1.

📒 Files selected for processing (1)

cli/src/build/react_native_noir.rs

🚧 Files skipped from review as they are similar to previous changes (1)

cli/src/build/react_native_noir.rs

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📝 Walkthrough

Walkthrough

The React Native Noir Android builder now uses a shared Cargo target directory, stages libraries by ABI, and publishes the completed JNI directory. It validates architectures before modifying output. React Native configuration helpers are now public.

Changes

React Native Android build

Layer / File(s)	Summary
Expose React Native build helpers `mopro-ffi/src/app_config/react_native.rs`	`android_abi_for_triple` and `remove_unrequested_wasm_stubs` are now public.
Build and install architecture libraries `cli/src/build/react_native_noir.rs`	The builder validates architectures, uses `project_dir/target`, passes `--no-jniLibs`, stages each library in its ABI directory, publishes the staging directory, sets `CARGO_TARGET_DIR`, and derives the bindgen profile directory from `mode.as_str()`.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 7e33f

The Android build change stages JNI libraries for each requested ABI and rejects empty architecture lists before changing output. No unresolved merge-readiness risk is identified.

Sequence Diagram(s)

sequenceDiagram
  participant build
  participant build_android_once
  participant Cargo
  participant install_jni_lib
  participant publish_jni_libs

  build->>build_android_once: Build each architecture with target_dir
  build_android_once->>Cargo: Set CARGO_TARGET_DIR and pass --no-jniLibs
  Cargo-->>build_android_once: Produce architecture library
  build->>install_jni_lib: Copy library to ABI staging directory
  install_jni_lib->>publish_jni_libs: Provide completed jniLibs_next directory
  publish_jni_libs->>publish_jni_libs: Replace live jniLibs directory

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 62.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: preserving all requested Android ABIs in jniLibs for Noir React Native builds.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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moven0831

Hi, thanks for the PR. Just left a review and would love to hear back from you.

moven0831 · 2026-09-01T15:02:31Z

+    if jni_libs.exists() {
+        fs::remove_dir_all(&jni_libs).context("Failed to clear jniLibs")?;
+    }


ubrn does its rm -rf jniLibs after cargo_build_all returns, whereas this wipes up front. So if a later arch fails (e.g. missing Zig, bad bb prebuilt), we're left with a partial tree where a complete one used to be, and since mopro create/update merges rather than replaces, that partial tree ships and Gradle hits the same missing-.so error this PR is fixing.

Could we stage each arch into a temp dir and swap once the loop finishes (like the build/tmp/<uuid> pattern the other builders use), or just move the wipe below the loop? Happy either way, curious what you think.

You are right, I missed this case. We can stage each lib into a temp dir but how about using a jniLibs’s sibling dir instead of build/tmp/? This way we can simply install the ABIs from target to the sibling dir and once every build is successful and the loop exits we remove the old jnilibs dir and rename the sibling dir: “jniLibs”. this way we have no cross tree move/rename. If one target fails we will simply fallback to the old jniLibs and the half built jnilibs sinbling gets deleted at the start of the new run

That sounds good to me. Let's go for this one. Thank you!

…t jniLibs directory

… bindgen

…tial tree case

coderabbitai

Actionable comments posted: 2

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Inline comments:
In `@cli/src/build/react_native_noir.rs`:
- Line 69: Move the empty Android architecture-list validation using
android_arch_strings.first() before publish_jni_libs and any cleanup or staging
operations. Preserve the existing failure behavior for empty input while
ensuring publish_jni_libs only runs after a non-empty architecture list is
confirmed.
- Line 130: Update build_android_once so extra_env overrides are applied before
the default CARGO_TARGET_DIR assignment, keeping the computed target_dir
authoritative; alternatively, reject CARGO_TARGET_DIR in
ArchBuildConfig::extra_env. Ensure install_jni_lib continues reading artifacts
from target_dir/<arch>/<profile>/<library> without being redirected.

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ℹ️ Review info

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Configuration used: defaults

Review profile: CHILL

Plan: Team

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📥 Commits

Reviewing files that changed from the base of the PR and between f0b80e4 and 23640e9.

📒 Files selected for processing (2)

cli/src/build/react_native_noir.rs
mopro-ffi/src/app_config/react_native.rs

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… CARGO_TARGET_DIR

moven0831 requested changes Sep 1, 2026

View reviewed changes

bl0nnn added 4 commits September 4, 2026 16:52

fix: noir android react-native multi arch invocation generates correc…

f48831f

…t jniLibs directory

made android_abi_for_triple function public

c89d522

format rust code in react_native_noir.rs and use CARGO_TARGET_DIR for…

4f38bc9

… bindgen

stage Android jniLibs in a sibling dir before publishing to avoid par…

23640e9

…tial tree case

bl0nnn force-pushed the fix-rn-noir branch from f0b80e4 to 23640e9 Compare September 4, 2026 16:09

coderabbitai Bot reviewed Sep 4, 2026

View reviewed changes

Comment thread cli/src/build/react_native_noir.rs

Comment thread cli/src/build/react_native_noir.rs Outdated

address coderabbit review for completeness: precheck empty archs, pin…

7e33fc1

… CARGO_TARGET_DIR

vivianjeng merged commit 1dd120b into zkmopro:main Sep 5, 2026
38 of 40 checks passed

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Fix: keep all Android ABIs in jniLibs for Noir React Native - #726

Fix: keep all Android ABIs in jniLibs for Noir React Native#726
vivianjeng merged 5 commits into
zkmopro:mainfrom
bl0nnn:fix-rn-noir

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