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Configuration for uniffi-bindgen-react-native

The configuration yaml file is a collection of configuration options used in one or more commands.

The file is designed to be easy to start. A minimal configuation would be:

rust:
  directory: ./rust
  manifestPath: Cargo.toml

Getting started from here would require a command to start the Rust:

cargo init --lib ./rust
cd ./rust
cargo add uniffi

YAML entries

rust

rust:
    repo: https://github.com/example/my-rust-sdk
    branch: main
    manifestPath: crates/my-api/Cargo.toml

In this case, the ubrn checkout command will clone the given repo with the branch/ref into the rust_modules directory of the project. Note that instead of branch you can also use rev or ref.

If run a second time, no overwriting will occur.

The manifestPath is the path relative to the root of the Rust workspace directory. In this case, the manifest is expected to be, relative to your React Native library project: ./rust_modules/my-rust-sdk/crates/my-api/Cargo.tml.

rust:
    directory: ./rust
    manifestPath: crates/my-api/Cargo.toml

In this case, the ./rust directory tells ubrn where the Rust workspace is, relative to your React Native library project. The manifestPath is the relative path from the workspace file to the crate which will be used to build bindings.

bindings

This section governs the generation of the bindings— the nitty-gritty of the Rust API translated into Typescript. This is mostly the location on disk of where these files will end up, but also has a second configuration file.

bindings:
    cpp: cpp/bindings
    ts: ts/bindings
    uniffiToml: ./uniffi.toml

The uniffi.toml file configures custom types, to further customize the conversion into Typescript data-types.

If missing, the defaults will be used:

bindings:
    cpp: cpp/generated
    ts: ts/generated

android

This is to configure the build steps for the Rust, the bindings, and the turbo-module code for Android.

This section can be omitted entirely, as sensible defaults are provided. If you do want to edit the defaults, these are the members of the android section with their defaults:

android:
    directory: ./android
    cargoExtras: []
    targets:
    - arm64-v8a
    - armeabi-v7a
    - x86
    - x86_64
    apiLevel: 21
    jniLibs: src/main/jniLibs
    packageName: <DERIVED FROM package.json>
    codegenOutputDir: <DERIVED FROM package.json>

The directory is the location of the Android project, relative to the root of the React Native library project.

targets is a list of targets to build for. The Rust source code is built once per target.

cargoExtras is a list of extra arguments passed directly to the cargo build command.

apiLevel is the minimum API level to target: this is passed to the cargo ndk command as a --platform argument.

Tip

Reducing the number of targets to build for will speed up the edit-compile-run cycle.

packageName is the name of the Android package that Codegen used to generate the TurboModule. codegenOutputDir is the path under which Codegen stores its generated files. Both are derived from the package.json file, and can almost always be left.

To customize the packageName, you should edit or add the entry at the path codegenConfig/android/javaPackageName in package.json.

To customize the codegenOutputDir, you should edit or add the entry at the path codegenConfig/outputDir/android in package.json.

Warning

Note that for Android the outputDir value in package.json needs to have a matching entry under dependency/platforms/android/cmakeListsPath in react-native.config.js. For example, if you set the Android output directory in package.json to android/tmp, the cmakeListsPath value in react-native.config.js needs to be set to tmp/jni/CMakeLists.txt.

ios

This is to configure the build steps for the Rust, the bindings, and the turbo-module code for iOS.

This section can be omitted entirely, as sensible defaults are provided. If you do want to edit the defaults, these are the members of the ios section with their defaults:

ios:
    directory: ios
    cargoExtras: []
    targets:
    - aarch64-apple-ios
    - aarch64-apple-ios-sim
    xcodebuildExtras: []
    frameworkName: build/MyFramework
    codegenOutputDir: <DERIVED FROM package.json>

The directory is the location of the iOS project, relative to the root of the React Native library project.

targets is a list of targets to build for. The Rust source code is built once per target.

cargoExtras is a list of extra arguments passed directly to the cargo build command.

xcodebuildExtras is a list of extra arguments passed directly to the xcodebuild command.

codegenOutputDir is the path under which Codegen stores its generated files. This is derived from the package.json file, and can almost always be left.

To customize the codegenOutputDir, you should edit or add the entry at the path codegenConfig/outputDir/ios in package.json.

web

This is to configure the build steps for the Rust, the bindings, and the turbo-module code for iOS.

This section can be omitted entirely, as sensible defaults are provided. If you do want to edit the defaults, these are the members of the ios section with their defaults:

web:
    manifestPath: rust_modules/wasm/Cargo.toml
    manifestPatchFile: null
    wasmCrateName: <DERIVED FROM package.json>
    features: []
    defaultFeatures: true
    workspace: false
    runtimeVersion: <DERIVED FROM UBRN>
    cargoExtras: []
    target: web
    wasmBindgenExtras: []
    entrypoint: <DERIVED FROM package.json> or "src/index.web.ts"
    tsBindings: <SAME AS bindings/ts>

The manifestPath is the path to the generated wasm-crate. The location of paths for the generate wasm wasm-crate and for the rust files for generate wasm bindings are derived from this path.

The manifestPatchFile is a path to a TOML file that will be used to patch merge on top of the generated wasm-crate Cargo.toml. This is extremely useful when customizing the manifest. e.g. when overriding dependencies in the target crate.

The wasmCrateName is the name of the wasm-crate, derived from the package.json name property.

The features array is used to build the target crate, and then added to the wasm crate’s Cargo.toml.

The defaultFeatures flag pairs with the features array: it is used to build the target crate (toggling the --no-default-features command line option) and then added to the wasm crate’s Cargo.toml, as default-features.

The boolean workspace controls if the wasm crate is part of an existing Rust workspace. The default value assumes that the target crate doesn’t know anything about the wasm-crate, so the wasm-crate is in its own workspace. If the target crate is in a workspace, and that can be changed, then this setting can be changed to true. Tip: members can contain globs to point to crates that don’t yet exist.

runtimeVersion is the version of uniffi-runtime-javascript crate. By default this is the exact current version of uniffi-bindgen-react-native, so currently =0.29.0-1.

cargoExtras is a list of extra arguments passed directly to the cargo build command when building for wasm32-unknown-unknown.

target is the passed to wasm-bindgen or wasm-pack. Default is web. This is likely only useful if you’re customizing the way the WASM bundle is loaded.

wasmBindgenExtras is a list of extra arguments passed directly to wasm-bindgen.

entrypoint is the filepath of the file which loads and exports the bindings. By default this is taken from the browser property of package.json, or src/index.web.ts if that is missing.

tsBindings is the directory where the typescript bindings are generated. This overrides the bindings/ts directory.

Warning

Uniffi is unable to process WASM files directly, so has to use a lib.a file built for the build environment.

Any uniffi::export or uniffi derive macros should not be toggled on and off based on the target architecture. If you want wasm specific uniffi bindings, you should use a feature instead, and add it to the features list in this file.

turboModule

This section configures the location of the Typescript and C++ files generated by the generate jsi turbo-module command.

If absent, the defaults will be used:

turboModule:
    cpp: cpp
    ts: <DERIVED FROM package.json>
    spec: <DERIVED FROM package.json>
    entrypoint: <DERIVED FROM package.json>

The default entrypoint is derived from the react-native entry in the package.json, and if missing, src/index.tsx.

The spec is the name of the Codegen spec, e.g. NativeModule. By default it is derived from the codegenConfig/name property in package.json.

The ts directory is used for the Codegen spec NativeModule.ts, and is the default is taken from the codegenConfig/jsSrcDir property in package.json.

The Typescript files are the index.tsx file, and the Codegen installer file.

Info

By default, the index.tsx file is intended to be the entry point for your library.

If this is not the case—e.g. you want to do use the Rust as part of a larger library, then change the entrypoint to something other than the package.json value.

noOverwrite

This list of glob patterns of file that should not be generated or overwritten by the --and-generate flag, and the generate jsi turbo-module and generate wasm wasm-crate commands.

This is useful if you have customized one or more of the generated files, and do not want lose those changes.

For example, if you want to add C++ files to the library, you may want to change the build files.

noOverwrite:
    - "*.podspec"
    - CMakeLists.txt

You can generate the build files once then not overwrite them. Once you excluded the files, they can be safely edited.