Grazel

Grazel stands for Gradle to Bazel. A Gradle plugin to migrate Android projects to Bazel build system in an incremental and automated fashion.

Components

• Gradle plugin
• A Kotlin Starlark DSL to generate Starlark code in a type-safe way.
• Grab Bazel Common - Custom rules to bridge the gap between Gradle/Bazel.

Features

• Generate BUILD.bazel, WORKSPACE for given Android project and reduce the overall migration effort.
• Setup hybrid build to build part of project graph to build with Bazel and rest with Gradle.
• Minimal source changes to codebase - supported by Grab Bazel Common.
• Gradle Configuration as source of truth.

For documentation and usage instructions, please visit website.

How it works

It works by automatically generating Bazel scripts for given Android project based on your Gradle configuration. For simple projects, it should be able to migrate, fully build and launch the app with bazel mobile-install //<target-name>.

For example, for the following Gradle configuration:

apply plugin: "com.android.library"
apply plugin: "kotlin-android"

android {
    compileSdkVersion rootProject.compileSdk
    defaultConfig {
        minSdkVersion rootProject.minSdk
        targetSdkVersion rootProject.targetSdk
        versionCode 1
        versionName "1.0"
    }
}

dependencies {
    implementation project(":app")
    implementation project(":base")
    implementation "androidx.test.espresso:espresso-idling-resource:3.2.0"
}

Grazel's migrateToBazel task generates the following build script:

load("@io_bazel_rules_kotlin//kotlin:kotlin.bzl", "kt_android_library")

kt_android_library(
    name = "quiz",
    srcs = glob([
        "src/main/java/**/*.kt",
    ]),
    custom_package = "com.google.samples.apps.topeka.quiz",
    manifest = "src/main/AndroidManifest.xml",
    resource_files = glob([
        "src/main/res/**",
    ]),
    visibility = [
        "//visibility:public",
    ],
    deps = [
        "//app",
        "//base",
        "@maven//:androidx_test_espresso_espresso_idling_resource",
    ],
)

See migration capabilities for supported features. In advanced cases, where entire project might not be migratable, it migrates part of the graph and sets up hybrid build where part of the graph can be built with Bazel and rest with Gradle.

Resources

• Grab's migration journey from Gradle to Bazel via automation - Build Meetup'21.

License

Copyright 2022 Grabtaxi Holdings PTE LTD (GRAB)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.