Welcome Android Open Source Project (AOSP) to the Bazel ecosystem

After significant investment in understanding how best to build the Android Platform correctly and quickly, we are pleased to announce that the Android Platform is migrating from its current build systems (Soong and Make) to Bazel. While components of Bazel have been already checked into the Android Open Source Project (AOSP) source tree, this will be a phased migration over the next few Android releases which includes many concrete and digestible milestones to make the transformation as seamless and easy as possible. There will be no immediate impact to the Android Platform build workflow or the existing supported Android Platform Build tools in 2020 or 2021. Some of the changesto support Android Platform builds are already in Bazel, such as Bazel’s ability to parse and execute Ninja files to support a gradual migration.

Migrating to Bazel will enable AOSP to:

• Provide more flexibility for configuring the AOSP build (better support for conditionals)
• Allow for greater introspection into the AOSP build progress and dependencies
• Enable correct and reproducible (hermetic) AOSP builds
• Introduce a configuration mechanism that will reduce complexity of AOSP builds
• Allow for greater integration of build and test activities
• Combine all of these to drive significant improvements in build time and experience

The benefits of this migration to the Bazel community are:

• Significant ongoing investment in Bazel to support Android Platform builds
• Expansion of the Bazel ecosystem and community to include, initially, tens of thousands of Android Platform developers and Android handset OEMs and chipset vendors.
• Google’s Bazel rules for building Android apps will be open sourced, used in AOSP, and maintained by Google in partnership with the Android / Bazel community
• Better Bazel support for building Android Apps
• Better rules support for other languages used to build Android Platform (Rust, Java, Python, Go, etc)
• Strong support for Bazel Long Term Support (LTS) releases, which benefits the expanded Bazel community
• Improved documentation (tutorials and reference)

The recent check-in of Bazel to AOSP begins an initial pilot phase, enabling Bazel to be used in place of Ninja as the execution engine to build AOSP. Bazel can also explore the AOSP build graph. We're pleased to be developing this functionality directly in the Bazel and AOSP codebases. As with most initial development efforts, this work is experimental in nature. Remember to use the currently supported Android Platform Build System for all production work.

We believe that these updates to the Android Platform Build System enable greater developer velocity, productivity, and happiness across the entire Android Platform ecosystem.

By Joe Hicks on behalf of the Bazel and AOSP infrastructure teams