Inline modules reference

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A reference of Expo inline modules.

Warning: Inline modules are currently experimental. The API is subject to breaking changes.

Inline modules let you write native module code (Kotlin and Swift) directly in your Expo project directory, without creating a separate Expo module package. Expo discovers these files automatically and includes them in the build.

Configuration

`expo.experiments.inlineModules`

When defined, enables inline modules functionality in Expo CLI and Expo Modules Autolinking.

app.json

{
  "expo": {
    "experiments": {
      "inlineModules": {}
    }
  }
}

`expo.experiments.inlineModules.watchedDirectories`

Configures in which directories the inline modules can be created.

app.json

{
  "expo": {
    "experiments": {
      "inlineModules": {
        "watchedDirectories": ["app", "src"]
      }
    }
  }
}

Files inside nested directories will also be used. For example, if watchedDirectories = ["app"] is defined in the app config, and a module file such as app/nested/directory/SomeModule.kt exists in a nested path, then SomeModule can be used in your app.

A directory in watchedDirectories:

Needs to be inside a TypeScript/JavaScript project. This means it needs to have an ancestor in the directory tree that has package.json. For example, "watchedDirectories": ["app", "src/some/directory", pathToOtherProject] should work and "watchedDirectories": ["/", pathToFolderNotInNodeProject] won't.
Cannot be the whole project directory, for example,"./", nor an ancestor of it (for example ../).
Cannot be a subdirectory of the other directory in watchedDirectories. For example, watchedDirectories cannot be ["app", "app/nested/directory"], you can just set watchedDirectories to ["app"].
Cannot contain special characters like " ", "(", ")", "$". This means you cannot have "app/(tabs)" in the watchedDirectories, but you can have "app" and it should still use native files from "app/(tabs)" directory.

You need to run npx expo prebuild after changing the app config, for it to take effect.

Naming convention

The inline module file name has to match the native module name (which needs to be unique in your whole app). If you have a SimpleModule.kt, then the inline module inside it has that file name. For example:

// SimpleModule.kt
// ...
class SimpleModule: Module() { // Note that the class name has to match the filename.
    public func definition() -> ModuleDefinition {
        // Name("SimpleModule") // Note that `Name` also has to match the filename. So you can just omit it.
    }
}