🍔 TLDR

• the aim of this project is to implement a sane DX and a CI/CD workflow using Github Actions and Expo EAS
• we have 3 builds/apps: Development, Staging and Preview
• developers can build features using a browser
• the UI team can review UI components using Chromatic/Storybook
• the whole team can view updates for each of these 3 apps along the development process

⚡️ Tech

• Yarn
• TypeScript
• react-native
• Expo
• NextJS
• Solito
• Tamagui
• Storybook
• Jest, testing-library
• Turbo

🔥 About & Motivation

This is a monorepo for an Expo + NextJS app ⚡️

While our main objective is to develop a mobile app, now thanks to Solito and Tamagui we can target the web also. Just Tamagui alone brings great value due to its performance and theme-ui styles, while Solito provides cross-platform navigation.

react-native development is a bit tedious compared to web development, requiring testing on different platforms (iOS, Android), different OS versions, and different screen sizes. Even the processes of app building, submission and updating can get complicated without Expo. This is why this repo aims to easen the effort when it comes to native development, while implementing quality checks and CI/CD flows.

In this regard, the main reason for choosing to have web compatibility is the Developer Experience. From my personal experience building react-native apps, working with just the Simulator to build UIs can get frustrating, like when debugging with an attached Chrome Dev Tools instance (can't use Inspect Element on DIVs to tinker with styles, for example) or using the in-app injected Debugger (sort of a dumbed down Dev Tools, not really productive). But with this stack, we can build our mobile app using the browser, as you would do with a normal web app. Sure, one might implement mobile-specific features which won't work on web, so in this case they have to be properly handled, but in our case we're more interested to use a browser for UI development especially. There are some unsupported react-native APIs in react-native-web, which is used by NextJS and Storybook, but as long as we don't hit these limitations, we can continue using web.

Another good reason is Tamagui itself. It has the best performance compared to any other react-native UI libs.

Another reason for organizing everything in a monorepo is because we're targeting 2 different platforms (web & mobile), each having its own config. Overall, we're keeping each package clean of unwanted dependencies and with their own specific structure and configuration that are easy to follow.

This monorepo is the result of:

• initial scaffold using npm create tamagui (see the docs)
• getting some inspiration from tamagui-kitchen-sync for adding Storybook to it (link)
• adding turbo as a build and task runner cache system (link)
• using Yarn Workspaces with plugins (docs)
• tweaking tsconfig.json and package.json for each workspace package to glue them together nicely with TypeScript Project References and Path Aliases (docs). One useful trick was to define path aliases with the same name as the ones defied by the workspace packages; this way, the code editor will jump on click to source, instead of node_modules
• setting up build, format, lint, typecheck for each package
• setting up husky with pre-commit, commitlint and lint-staged hooks
• setting up semantic-release for apps/expo
• getting some inspiration for Github Actions cache from nextjs-monorepo-example (link)
• setting up a productive development workflow involving Github Actions + Chromatic/Storybook + Expo EAS (chromatic docs, EAS docs)
• overall nitting and bolting everything together, occasionally with some help from the fantastic Discord communities of Tamagui, Turbo and Expo

An easier alternative for setting up a monorepo would've been NX (link), which I tried initially and didn't work out because:

• you can leverage the full power of NX only in its integrated mode and not in package mode
• integrated means you have only one root package.json + TS path aliases, and each app configuration is black-boxed behind NX custom config generators
• you lose the flexibility of running custom package.json commands for your internal packages
• if choosing package mode, you would be better off to ditch NX completely and manually configure Yarn + TypeScript + Turbo as I did
• NX enforces that each custom environment variable has to be prefixed with NX_ while packages like tamagui expect exactly TAMAGUI_TARGET or APP_VARIANT
• overall, individual package.jsons with dotenv do the trick

🗂 Directory structure

• apps
  • expo
  • next
  • storybook
  • tests
• packages shared packages across apps
  • app you'll be importing most files from app/
    • features (don't use a screens folder, instead organize by feature). We should organize our code with respect to Domain Driven Design (blog article)
    • provider (all the providers that wrap the app, and some no-ops for Web.)
    • navigation Next.js has a pages/ folder. React Native doesn't. This folder contains navigation-related code for RN. You may use it for any navigation code, such as custom links.
  • eslint-config-custom as a global ESLint config, used in packages as { extends: ["custom", ...] }
  • tsconfig for specific TypeScript configuration for each package
  • ui for our dumb UI components
  • backend - not yet in the project, but will host our Supabase PostgreSQL Prisma schemas, Deno edge functions + optionally tRPC. One useful backend feature will be to trigger user notifications. Can get some inspiration from the T3 stack

The dependency graph looks like this:

🛠️ Prerequisites for setting everything up

• create an Expo account and a new Expo team
• create a Turbo team
• create a Chromatic account
• search this project for "REPLACE-ME" and replace stuff accordingly
• go over Prerequisites for development as described below and make sure everything works: running Storybook, running the app in Next, simulators, on your device with Expo
• go over Setup Github Actions as described below
• create your first builds with Expo as described in App variants below
• at this point you can safely start developing as described in Workflow below: Github Actions, Chromatic updates and EAS Updates should work as expected

📱 App variants

• see eas.json
• builds are real apps with different identifiers: dev.com.REPLACE-ME, staging.com.REPLACE-ME, preview.com.REPLACE-ME, see app.config.ts, docs, expo/package.json build commands
• for first time builds, use:
  • yarn build:all:dev
  • yarn build:all:staging
  • yarn build:all:preview
• 2 platforms x 3 variants = 6 builds. They can be found here
• all builds should have 1.0.0 version. They should only be rebuilt when the runtime policy of sdkVersion kicks in, meaning when we're forced to update if the Expo SDK version changes, see app.json, docs. What changes automatically after each release is buildNumber (for iOS) and versionCode (for Android)
• your team has to enable Developer mode to be able to run these apps
• updates to these apps are delivered via EAS Update (docs), instead of always building new app versions on each release (the Expo free tier offers only 20 builds / month and 1000 updates, so we prefer leveraging EAS Updates)
• The Development app is useful only in tandem with yarn start:devclient to preview live changes from a developer's machine. Could be used for pair programming.
• The Staging app is updated on each opened PR. Useful for code reviews (limitation: 1 PR to be opened at a time)
• The Preview app is updated on each new git release (merges to main) and acts as an exact preview of the Production app (which hasn't been built yet) used for testing before an official release. Team demos use this app.

🎬 Github Actions setup

• set the following secrets
  • CHROMATIC_PROJECT_TOKEN - you can get one after you create a Chromatic project
  • EXPO_TOKEN - get it from your Expo account
  • EXTENDED_GITHUB_TOKEN - this is a Github Personal Access Token, get one from your account; needs write access. Used by semantic-release to push new tags
  • SLACK_WEBHOOK - a Slack webhook configured to route messages to a channel, from Github Actions
  • TURBO_TEAM - follow Turbo docs how to create a team
  • TURBO_TOKEN - see Turbo docs
• create the following environment variables:
  • for staging environment
    • APP_VARIANT=staging
    • TAMAGUI_TARGET=native
  • for preview environment
    • APP_VARIANT=preview
    • TAMAGUI_TARGET=native

👨🏻‍💻 Prerequisites for development

• install Android Studio Emulator
• install iOS Simulator
• install Flipper (useful for debugging RN apps)
• join the Expo project (invites were sent)
• join the Chromatic project, here
• install the development, staging & preview builds on your personal device, taken from here
• run npm install -g eas-cli . For more info check EAS Build
• read the docs for Expo, Tamagui, Turbo

🏁 Start the app

• run yarn to install dependencies
• run yarn start:expo to start Expo
• run yarn start:next to start Next
• run yarn start:sb to start Storybook

🏋️ Workflow

1. The developer creates a new branch off main
2. Starts Storybook yarn start:sb and Expo yarn start:expo

• mainly uses Chrome + Storybook for UI development in packages/ui
• can also use Chrome + NextJS for app logic development in packages/app - run yarn start:next
• checks his changes inside the iOS Simulator and Android Studio (press "i" / "a" in the console)
• checks the app on his real mobile device using the consle QR Code
• can share his changes live before opening a PR with other devs in 2 ways:
  • using Expo Go, by running yarn start:tunnel and sharing the QR code with others
  • using the Development Build Client (has to be installed by others), running yarn start:devclient and sharing the QR Code
  • the difference between these two is that the Development Build Client is more closer to the production app
• checks the minified app running start:ios:prod and start:android:prod. Same as yarn start:expo, but it's a minified and closer to production build. Sometimes you can catch some 3rd party lib bugs this way.

3. Commits his changes

• commit messages must respect the conventional commit format, eg: fix(login screen): adjusted font size
• on commit, husky runs npx lint-staged --allow-empty && yarn g:run-all-checks, where the checks are: turbo run typecheck lint format:check test build --parallel --since=HEAD^1

4. Pushes his changes and opens a new PR

• Gihub Actions kick in:
  • ci-build-test.yml: runs Typecheck, Lint, Format check, Build, Unit tests for all configured packages
  • ci-monorepo-integrity.yml: Check for duplicate dependencies and yarn constraints
  • cd-chromatic.yml: Deploys the Storybook to Chromatic to be reviewed by the team ❗️
  • cd-eas-update-staging.yml: Updates the Staging app to be reviewed by the team ❗️. Also a QR code is automaticallty generated in the PR comments and links to the Expo Go client.
• requires at least 1 reviewer to accept the PR

5. On merging the PR to main, the same Github Actions run again, with the following additional actions:

• ci-semantic-release.yml: Runs semantic-release which bumps the version of apps/expo/package.json, bumps buildNumber and versionCode for apps/expo/app.json, updates apps/expo/CHANGELOG.md by aggregating the conventional commit messages, creates a new git tag version and a new git release based on it. See Releases. Please join the #REPLACE-ME-github Slack channel for updates 📫
• cd-eas-update-preview.yml: Triggered by a new git release, updates the Preview app

🏎️ Performance

• we have yet to document the bundle size, but my memory recalls 1.9M for this barebone project
• Tamagui by itself delivers great performance with respect to style updates and animations, leaving others in dust
• Github Actions CI checks take around 10 minutes without Turbo cache, and around 2-3 minutes with Turbo cache
• Manual Expo Builds take around 10 minutes using the Free Trial (we anyway trigger new builds very rarely because we leverage CI EAS hot Updates instead). Putting this in context, building in CI by yourself with fastlane takes around 1H from my experience (yeah very debatable, but still).

📐 Mobile app architecture and other considerations

• which libs to use for state management and data fetching? RTK handles both well in an integrated fashion. Jotai is another strong candidate, as it has React-Query integration and tRPC integration (we want to use tRPC on the backend)

🆕 Add new dependencies

Pure JS dependencies

If you're installing a JavaScript-only dependency that will be used across platforms, install it in packages/app:

cd packages/app
yarn add date-fns

Native dependencies

If you're installing a library with any native code, you must install it in apps/expo:

cd apps/expo
yarn add react-native-reanimated

📟 NPM Commands

• go over each package.json to get accustomed with NPM commands specific to each package
• the root package.json should contain only monorepo specific commands

Notes

• this repo serves as a good starting point for development with Expo EAS, and will be improved in terms of workflow and tooling as we progress and discover new stuff that we might need, for example:
  • for Storybook, we might swap Webpack in favor of Vite or Turbopack because of the slow build time
  • better testing architecture? Right now apps/tests is configured to run user interaction tests with testing-library (docs). We might want to add Snapshot testing and E2E Detox tests. Or picking between moving jest to each individual package VS root jest config with projects: [...]. Not a priority right now.
  • Tamagui is being actively developed and sometimes breaking changes occur. We have to keep an eye on it.
  • Running Turbo with --since=HEAD^1 should be refactored to select the PR's first commit hash instead
  • no concrete UI components have been developed up to this point, and we should develop them along with a custom theme. We don't want to repeat text sizes, colors and spacings everywhere.
• missing from our workflow is the production distribution of the app to stores, and most probably it won't be integrated with Continous Deployment, because we want to control this sensible process manually. But we want to trigger Continous Deployment EAS Updates to the production app on pushing to a production branch, but hasn't been configured yet. There are some Deployment patterns and we will pick one at the right time. Right now we're using eas update --branch staging/preview in our Github Actions which are linked to the staging/preview channels. These Expo branches shouldn't be confused with git branches: a build corresponds to a release channel, and these "branches" are pointed to channels. When using the eas update command, regardless of the git branch you're on, you can specify --branch so that your code can be routed to the specific channel. --auto sets the branch to the current git branch, but we're not using that.
• some tweaking is needed around file globs used in Turbo and Github Actions, to prevent running unnecessary commands (eg: it doesn't make sense to trigger a typecheck when only the README.md file was updated)
• we should be really careful when upgrading react, react-native, react-native-web, tamagui. Experience and public Github issues show us that things can break really easily for lots of people at once and often. Manual and automated tests are key.
• before going public, we should scan and update our dependencies with Snyk, update this readme with respect to Release Management and check again all permissions regarding this process

FAQ

• if yarn ios or npx pod-install fails with:

  Couldn't install Pods. Updating the Pods project and trying again...
  Command `pod install` failed.
  └─ Cause: Invalid `Podfile` file:
  [!] Invalid `RNGestureHandler.podspec` file: undefined method `exists?' for File:Class.
  

  Check this facebook/react-native#35807 (comment)

• devs are encouraged to update this section any time they run into unexpected problems