Build performance¶

Rust builds are usually the slowest part of a build with this plugin. These options help.

Build only what you need¶

• Debug builds only compile the host platform for JVM, and the host's ABI(s) for Android. Use release builds (-PreleaseBuild=true) only for publishing.
• Restrict the Android debug ABIs to your device with -PandroidAbis=arm64-v8a or cargo { androidDebugAbis.add("arm64-v8a") }. See Targets.
• Only declare the Kotlin targets you need. Every Kotlin/Native target is a separate Rust build.

Shared Cargo target directory¶

By default the plugin uses Cargo's normal target directory, as reported by cargo metadata. Inside one Gradle build, all modules of a Cargo workspace already share it.

If the same Rust sources are built from more than one Gradle build, for example an SDK checkout and an app that includes it through dependency substitution, point both builds at the same directory:

cargo {
    targetDirectory = rootProject.layout.projectDirectory.dir("cargo-build")
}

Setting the CARGO_TARGET_DIR environment variable has the same effect, without changing build scripts.

• The directory survives Gradle's clean. Delete it yourself when you need a fresh Rust build.
• Don't point it at a Gradle build directory. Kotlin and Android outputs stay project-local.
• In CI, persist it with the CI cache if separate jobs or runs should reuse it.

sccache¶

sccache caches Rust compilation across target directories and machines:

cargo {
    rustcWrapper = "sccache"
}

or set RUSTC_WRAPPER=sccache (or RUSTC_WORKSPACE_WRAPPER=sccache) before running Gradle. The wrapper is passed to every Cargo invocation and is part of the task inputs.

IDE sync¶

During an IntelliJ / Android Studio sync, the plugin generates the bindings so the IDE can resolve them, but skips the Kotlin/Native Rust builds. The first real build after a sync compiles them.