Autolinking

Autolinking finds the native code of the packages an app depends on, and builds it into the app. It runs on every run-desktop and init-desktop, and writes its output to desktop/autolink/, which is generated and git-ignored.

A package takes part by declaring platforms.desktop in its react-native.config.js:

react-native.config.js

module.exports = {
  dependency: {
    platforms: {
      desktop: {
        crate: 'rn-gpui-awesome-storage',
      },
    },
  },
};

What autolinking does

• Adds each Rust crate to the app's desktop/Cargo.toml as a dependency, and calls its rn_gpui_register function at startup.
• Compiles each cmake project and cppProvider into the app.
• Runs React Native Codegen over the specifications of every package with a codegenConfig, and compiles the generated C++ into the app.
• Generates the Rust and C++ spec glue for modules, and the typed glue for host components.
• Registers Fabric component descriptors and host components.
• Writes a [patch.crates-io] table into the app's desktop/Cargo.toml, which points core's crates at the copy the app installed and pins GPUI to core's revision. It is regenerated on every run, so leave it alone.
• Records the installed JavaScript engines.

platforms.desktop

Key	Type	Description
crate	string	The name of a Cargo crate in the package's desktop/ folder (or the package root). It must have an rn_gpui_register function.
path	string	The folder of the crate, when it is not desktop/ or the package root.
cmake	string	A folder with a CMakeLists.txt that adds C++ sources to the app.
cppProvider	string	The C++ function that creates a C++ TurboModule for each specification of the package.
cppSources	string[]	The C++ sources of the module, if they should not be found from cmake.
specs	string	The folder of the specifications, when codegenConfig.jsSrcsDir is not set. Defaults to src.
hostComponents	object[]	The host components the package provides: {name, measured?, nativeSurface?, container?}.
componentDescriptors	string[]	C++ identifiers of Fabric component descriptors to register.
componentHeaders	string[]	The headers that declare those descriptors. Required with componentDescriptors.
componentSources	string[]	Extra C++ sources for the components.
componentIncludeDirs	string[]	Extra include folders for the components.
componentSourcePackage	string	The package that componentSources and componentIncludeDirs are relative to. Defaults to the package itself.
componentCodegenPackage	string	The package whose component specifications Codegen runs over. For adapters.
sourceOverrides	object	Files of installed JavaScript packages that Metro replaces for desktop.
jsEngine	object	Declares the package as a JavaScript engine.

A hostComponents entry cannot be both measured and a container.

project.desktop

The app's own react-native.config.js carries build options under project.desktop:

react-native.config.js

module.exports = {
  project: {
    desktop: {
      prebuilt: 'auto', // 'auto' | 'always' | 'never'
    },
  },
};

prebuilt chooses whether React Native's C++ runtime is downloaded or built from source. See CLI.

Errors

Autolinking checks what it reads. A missing or duplicate component descriptor, an invalid crate name, a jsEngine entry that points at a file that does not exist, and a hostComponents entry that cannot be both measured and a container are all reported while linking, with the name of the package, and not later in the build.