Adding or changing turbo-module templates

In addition to generating the bindings between Hermes and Rust, uniffi-bindgen-react-native generates the files needed to run this as a turbo-module. The list of files are documented elsewhere in this book.

Templates are written for Askama templating library.

Changing the templates for these files is relatively simple. This PR is a good example of adding a file.

• Template files are in the codegen/templates directory.
• Template configuration are in codegen/mod.rs file.

Adding a new template

1. Add new template to the codegen/templates directory.
2. Add a new RenderedFile struct, which specifies the template, and its path to the files module in codegen/mod.rs.
3. Add an entry to the list of generated files in this book.

The template context will have quite a lot of useful information data-structures about the project; the most prominent:

• ModuleMetadata, which is generated from the lib.a file from the uniffi contents of the Rust library.
• ProjectConfig which is the in-memory representation of the YAML configuration file.
• CrateMetadata which is data about the crate derived from cargo metadata.

Testing changes

The ./scripts/test-turbo-modules.sh script runs a suite of tests, simulating the steps in the Getting Started tutorial:

• do the names of the ubrn generated files match up with the files builder-bob generated files?
• do generated identifiers in the ubrn generated files match up with those generated by builder-bob?
• does an Android app compile
• does an iOS app compile

If you want to test a particular configuration, you can use the command with a series of options:

Usage: ./scripts/test-turbo-modules.sh [options] [PROJECT_DIR]

Options:
  -A, --android                      Build for Android.
  -I, --ios                          Build for iOS.
  -C, --ubrn-config                  Use a ubrn config file.
  -T, --app-tsx                      Use a App.tsx file.

  -s, --slug PROJECT_SLUG            Specify the project slug (default: my-test-library).
  -i, --ios-name IOS_NAME            Specify the iOS project name (default: MyTestLibrary).

  -u, --builder-bob-version VERSION  Specify the version of builder-bob to use (default: latest).
  -k, --keep-directory-on-exit       Keep the PROJECT_DIR directory even if an error does not occur.
  -f, --force-new-directory          If PROJECT_DIR directory exist, remove it first.
  -h, --help                         Display this help message.

Arguments:
  PROJECT_DIR                        Specify the root directory for the project (default: my-test-library).

For example, to test if a configuration builds then runs:

fixtures=./integration/fixtures/turbo-module-testing
directory=/tmp/my-test-library
./scripts/test-turbo-modules.sh \
    --ubrn-config $fixtures/ubrn.config.yaml \
    --app-tsx $fixtures/App.tsx \
    --ios \
    --android \
    --keep-directory-on-exit \
    --force-new-directory \
    "$directory"

cd "$directory"
yarn example start