fjs Cargokit Build Tool

This package is the local Cargokit build tool used by fjs. It is based on the Flutter Rust Bridge Cargokit integration and is vendored here so the Flutter plugin can build Rust artifacts without depending on a globally installed Dart package.

The entrypoint is normally invoked through:

cargokit/run_build_tool.sh <command> ...

run_build_tool.sh creates a temporary Dart runner, compiles it to a kernel snapshot, and invalidates that snapshot when this package changes.

Commands

build-pod

Used by the iOS, macOS, and shared Darwin podspecs:

cargokit/run_build_tool.sh build-pod libfjs fjs

Flutter and CocoaPods provide the required CARGOKIT_* and Xcode deployment environment variables. The command builds the Rust crate for the active Darwin platform and copies libfjs.a into the configured build output directory.

build-gradle

Used by Android builds. Flutter/Gradle provide Android SDK, NDK, target platform, and output directories through CARGOKIT_* environment variables.

build-cmake

Used by desktop CMake-based builds. The command builds the Rust crate for the requested desktop target and copies the produced dynamic library into the configured output directory.

gen-key

Generates an Ed25519 key pair for signing precompiled Cargokit artifacts:

cargokit/run_build_tool.sh gen-key

Store the private key in CI secrets only. Put the public key in libfjs/cargokit.yaml.

precompile-binaries

Builds release Rust artifacts, signs them, and uploads them to a GitHub Release tag named precompiled_<crate-hash>:

PRIVATE_KEY=<hex-private-key> \
GITHUB_TOKEN=<github-token> \
cargokit/run_build_tool.sh precompile-binaries \
  --repository fluttercandies/fjs \
  --manifest-dir libfjs

Pass --target <rust-triple> one or more times to publish a subset of targets. When omitted, the tool builds targets that are buildable on the current host and adds Android targets when Android SDK options are provided.

verify-binaries

Checks that every configured precompiled artifact exists and that its signature matches libfjs/cargokit.yaml:

cargokit/run_build_tool.sh verify-binaries --manifest-dir libfjs

This command verifies per-target Cargokit artifacts. It does not validate the SwiftPM XCFramework zip; use tool/prepare_darwin_release.sh for that release path.

Configuration

Crate-level settings live in libfjs/cargokit.yaml:

precompiled_binaries:
  url_prefix: https://github.com/fluttercandies/fjs/releases/download/precompiled_
  public_key: <32-byte-ed25519-public-key-hex>

User-level settings are read from the nearest cargokit_options.yaml found by walking upward from CARGOKIT_ROOT_PROJECT_DIR:

use_precompiled_binaries: true
verbose_logging: false

Default behavior:

If Rustup is available, builds use local Rust source.
If Rustup is missing, builds try signed precompiled binaries.
use_precompiled_binaries: true opts in to precompiled downloads even when Rustup is available.
use_precompiled_binaries: false forces local Rust builds.

Darwin XCFramework Release Flow

CocoaPods and the Swift Package Manager artifact share the same Rust source and Cargokit build inputs, but the XCFramework is packaged by repository scripts:

tool/build_fjs_xcframework.sh --configuration Release
tool/prepare_darwin_release.sh --configuration Release

tool/build_fjs_xcframework.sh writes a temporary options file that sets use_precompiled_binaries: false, so the release XCFramework is built from the current local Rust source. tool/prepare_darwin_release.sh then creates build/darwin-release/fjs.xcframework.zip, writes the SwiftPM checksum, checks Darwin package metadata, and runs flutter pub publish --dry-run.

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