Expo Fingerprint

A library to generate a fingerprint from a React Native project.

@expo/fingerprint provides an API to generate a fingerprint (hash) of your project for use in determining compatibility between the native layer and JavaScript layer of your app. The hash calculation is configurable, but is by default derived from hashing app dependencies, custom native code, native project files, and configuration.

Installation

@expo/fingerprint is included with expo and expo-updates by default.

If you wish to use @expo/fingerprint as a standalone package, you can install it by running the command:

API Usage

import * as Fingerprint from '@expo/fingerprint';

CLI Usage

Configuration

@expo/fingerprint provides defaults that should work for most projects, but also provides a few ways to configure the fingerprinting process to better fit your app structure and workflow.

.fingerprintignore

Placed in your project root, .fingerprintignore is a .gitignore-like ignore mechanism used to exclude files from hash calculation. It behaves similarly but instead uses minimatch for pattern matching which has some limitations (see documentation for ignorePaths under Options).

For example, to skip a folder but keep some files:

# Ignore the entire /app/ios folder
/app/ios/**/*

# But still keep /app/ios/Podfile and /app/ios/Podfile.lock
!/app/ios/Podfile
!/app/ios/Podfile.lock

fingerprint.config.js

Placed in your project root, fingerprint.config.js allows you to specify custom hash calculation configuration beyond what is configurable in the .fingerprintignore.

For supported configurations, see Config and SourceSkips.

Below is an example fingerprint.config.js configuration, assuming you have @expo/fingerprint installed as a direct dependency:

/** @type {import('@expo/fingerprint').Config} */
const config = {
  sourceSkips: [
    'ExpoConfigRuntimeVersionIfString',
    'ExpoConfigVersions',
    'PackageJsonAndroidAndIosScriptsIfNotContainRun',
  ],
};
module.exports = config;

If you are using @expo/fingerprint through expo (where @expo/fingerprint is installed as a transitive dependency), you can import fingerprint from expo/fingerprint:

/** @type {import('expo/fingerprint').Config} */

Limitations

const { withInfoPlist } = require('expo/config-plugins');

const withMyPlugin = (config) => {
  return withInfoPlist(config, (config) => {
    config.modResults.NSLocationWhenInUseUsageDescription = 'Allow $(PRODUCT_NAME) to use your location';
    return config;
  });
};

export default ({ config }) => {
  config.plugins ||= [];
  config.plugins.push(withMyPlugin);
  config.plugins.push((config) => config);
  return config;
};

const { withInfoPlist } = require('expo/config-plugins');

const withMyPlugin = config => {
  return withInfoPlist(config, config => {
    config.modResults.NSLocationWhenInUseUsageDescription =
      'Allow $(PRODUCT_NAME) to use your location';
    return config;
  });
};

module.exports = withMyPlugin;

{
  "expo": {
    %%placeholder-start%%... %%placeholder-end%%
    "plugins": "./plugins/withMyPlugin"
  }
}

Constants

Methods

const fingerprint = await createFingerprintAsync('/app');
console.log(fingerprint);

const hash = await createProjectHashAsync('/app');
console.log(hash);

// Create a fingerprint for the project
const fingerprint = await createFingerprintAsync('/app');

// Make some changes to the project

// Calculate the diff
const diff = await diffFingerprintChangesAsync(fingerprint, '/app');
console.log(diff);

// Create a fingerprint for the project
const fingerprint = await createFingerprintAsync('/app');

// Make some changes to the project

// Create a fingerprint again
const fingerprint2 = await createFingerprintAsync('/app');
const diff = await diffFingerprints(fingerprint, fingerprint2);
console.log(diff);

Interfaces

Types

Enums