Updater library

This is the Rust side of the Shorebird code push system. This is built in Rust with a C API for easy calling from other languages, most notably for linking into libflutter.so.

The primary modification Shorebird makes to the stock Flutter engine is adding support for the updater library (this repo). The updater library is written in Rust and is used to update the code running in the Flutter app. The updater library is built as a static library and is linked into the Flutter engine during build time.

Parts

• library: Runtime library linked into Flutter Engine to unpack and apply updates. Build into libupdater.a and linked into libflutter.so.
• patch: Developer tooling to package Shorebird updates ("patches"). Built into patch.exe and downloaded and run by shorebird command line tool: https://github.com/shorebirdtech/shorebird/tree/main/packages/shorebird_cli.
• shorebird_code_push: The Dart bindings for communicating with the updater library from within a Flutter app. Published to pub.dev, usage is optional by developers.

Most interesting code is in the library directory. There is also a README.md in that directory explaining the design.

Developing

It's best to edit this repository from within an engine checkout. See BUILDING_ENGINE.md for instructions on how to set up an engine checkout.

The workflow I use involves 2 to 3 VSC windows:

1. Opening the engine src.

In that terminal I:

cd third_party/updater

2. To build the updater as part of the engine:

cargo ndk --target aarch64-linux-android build --release && \
    ninja -C ../../out/android_release_arm64 && say "done"

The cargo part should not be needed, but I haven't yet done the work to integrate the Rust code into the gn files for the Flutter engine yet.

I add say "done" to the end as linking can take several minutes for release Android builds.

3. In a second window, I open code third_party/updater. I do this because otherwise the rust_analyzer can't seem to find the rust code. We could fix this by adding the directory to the VSC workspace, but I'm not sure where we would put the workspace file in the first place. src is actually shorebirdtech/buildroot and is controlled via gclient by shorebirdtech/engine/DEPS.

4. In a third window I open my test app. e.g.:

flutter create test_app
cd test_app
shorebird init
shorebird release
code .

5. To run the test app with my local engine I use:

shorebird run --local-engine-src-path $HOME/Documents/GitHub/engine/src \
    --local-engine android_release_arm64

You may also need to build out/host_release once as flutter build looks for some Dart .dill files in host_release.

Coverage

We'd like to get to 100% coverage but aren't there yet.

https://github.com/taiki-e/cargo-llvm-cov is the best tool I've found for generating coverage reports.

Install: https://github.com/taiki-e/cargo-llvm-cov#installation

cargo llvm-cov will then generate the report.