This application is built with the following principles.
-
Data Flow - Ideally, this is how data flows through the app:
- Server pushes data to the disk of any client (Server -> Pusher event -> Action listening to pusher event -> Onyx). Currently the code only does this with report comments. Until we make more server changes, this steps is actually done by the client requesting data from the server via XHR and then storing the response in Onyx.
- Disk pushes data to the UI (Onyx -> withOnyx()/connect() -> React component).
- UI pushes data to people's brains (React component -> device screen).
- Brain pushes data into UI inputs (Device input -> React component).
- UI inputs push data to the server (React component -> Action -> XHR to server).
- Go to 1
-
Offline first
- All data that is brought into the app and is necessary to display the app when offline should be stored on disk in persistent storage (eg. localStorage on browser platforms). AsyncStorage is a cross-platform abstraction layer that is used to access persistent storage.
- All data that is displayed, comes from persistent storage.
-
UI Binds to data on disk
- Onyx is a Pub/Sub library to connect the application to the data stored on disk.
- UI components subscribe to Onyx (using
withOnyx()
) and any change to the Onyx data is published to the component by callingsetState()
with the changed data. - Libraries subscribe to Onyx (with
Onyx.connect()
) and any change to the Onyx data is published to the callback with the changed data. - The UI should never call any Onyx methods except for
Onyx.connect()
. That is the job of Actions (see next section). - The UI always triggers an Action when something needs to happen (eg. a person inputs data, the UI triggers an Action with this data).
- The UI should be as flexible as possible when it comes to:
- Incomplete or missing data. Always assume data is incomplete or not there. For example, when a comment is pushed to the client from a pusher event, it's possible that Onyx does not have data for that report yet. That's OK. A partial report object is added to Onyx for the report key
report_1234 = {reportID: 1234, isUnread: true}
. Then there is code that monitors Onyx for reports with incomplete data, and callsfetchChatReportsByIDs(1234)
to get the full data for that report. The UI should be able to gracefully handle the report object not being complete. In this example, the sidebar wouldn't display any report that doesn't have a report name. - The order that actions are done in. All actions should be done in parallel instead of sequence.
- Parallel actions are asynchronous methods that don't return promises. Any number of these actions can be called at one time and it doesn't matter what order they happen in or when they complete.
- In-Sequence actions are asynchronous methods that return promises. This is necessary when one asynchronous method depends on the results from a previous asynchronous method. Example: Making an XHR to
command=CreateChatReport
which returns a reportID which is used to callcommand=Get&rvl=reportStuff
.
- Incomplete or missing data. Always assume data is incomplete or not there. For example, when a comment is pushed to the client from a pusher event, it's possible that Onyx does not have data for that report yet. That's OK. A partial report object is added to Onyx for the report key
-
Actions manage Onyx Data
- When data needs to be written to or read from the server, this is done through Actions only.
- Public action methods should never return anything (not data or a promise). This is done to ensure that action methods can be called in parallel with no dependency on other methods (see discussion above).
- Actions should favor using
Onyx.merge()
overOnyx.set()
so that other values in an object aren't completely overwritten. - In general, the operations that happen inside an action should be done in parallel and not in sequence (eg. don't use the promise of one Onyx method to trigger a second Onyx method). Onyx is built so that every operation is done in parallel and it doesn't matter what order they finish in. XHRs on the other hand need to be handled in sequence with promise chains in order to access and act upon the response.
- If an Action needs to access data stored on disk, use a local variable and
Onyx.connect()
- Data should be optimistically stored on disk whenever possible without waiting for a server response. Example of creating a new optimistic comment:
- user adds a comment
- comment is shown in the UI (by mocking the expected response from the server)
- comment is created in the server
- server responds
- UI updates with data from the server
-
Cross Platform 99.9999%
- A feature isn't done until it works on all platforms. Accordingly, don't even bother writing a platform-specific code block because you're just going to need to undo it.
- If the reason you can't write cross platform code is because there is a bug in ReactNative that is preventing it from working, the correct action is to fix RN and submit a PR upstream -- not to hack around RN bugs with platform-specific code paths.
- If there is a feature that simply doesn't exist on all platforms and thus doesn't exist in RN, rather than doing if (platform=iOS) { }, instead write a "shim" library that is implemented with NOOPs on the other platforms. For example, rather than injecting platform-specific multi-tab code (which can only work on browsers, because it's the only platform with multiple tabs), write a TabManager class that just is NOOP for non-browser platforms. This encapsulates the platform-specific code into a platform library, rather than sprinkling through the business logic.
- Put all platform specific code in dedicated files and folders, like /platform, and reject any PR that attempts to put platform-specific code anywhere else. This maintains a strict separation between business logic and platform code.
- Install
node
&npm
:brew install node
- Install
watchman
:brew install watchman
- Install dependencies:
npm install
- Run
cp .env.example .env
and edit.env
to have your local config options.
You can use any IDE or code editing tool for developing on any platform. Use your favorite!
Ngrok makes the our locally-hosted web application appear to be hosted on a subdomain of ngrok.com. This allows us to avoid many of our cross-domain issues with our API and is required for doing local development on android or viewing images on mobile.
- Set up a permanent ngrok route
- Replace the value
NGROK_URL
in your.env
file with the ngrok route you just set up - Set the
USE_NGROK
in your.env
to true - Start ngrok with the name you previously set (
Expensidev/script/ngrok.sh thienlnam
)
Now, all of your API calls will be using the ngrok route.
- To run a Development Server:
npm run web
- To build a production build:
npm run build
- Changes applied to Javascript will be applied automatically via WebPack as configured in
webpack.dev.js
- To install the iOS dependencies, run:
npm install && cd ios/ && pod install
- To run a on a Development Simulator:
npm run ios
- If the app is booting on a simulator for the first time, run the following two commands:
xcrun simctl keychain booted add-root-cert ~/Expensidev/config/ssl/rootCA.crt #Adds root cert and trusts it xcrun simctl keychain booted add-cert ~/Expensidev/config/ssl/expensify.com.dev.pem #Adds .dev cert and trusts it
- Changes applied to Javascript will be applied automatically, any changes to native code will require a recompile
- To install the Android dependencies, run:
npm install
, thengradle
will install all linked dependencies - Running via
ngrok
is required to communicate with the API- Follow the instructions under the section
Setting up ngrok
- Follow the instructions under the section
- To run a on a Development Emulator:
npm run android
- Changes applied to Javascript will be applied automatically, any changes to native code will require a recompile
- To run the Development app, run:
npm run desktop
, this will start a new Electron process running on your MacOS desktop in thedist/Mac
folder.
If you don't have full-access to Expensify's development environment you will need to run the app against the production API.
- Copy the
.env.production
variables into your.env
file - Set
EXPENSIFY_URL_COM
environment variable to be empty (Note: this means it should beEXPENSIFY_URL_COM=
, not completely omitted) - To run the web app, run the Development Server:
npm run proxy
- To run the desktop app:
npm run desktop
- To run the iOS app:
npm run ios
- To run the Android app:
npm run android
Unit tests are valuable when you want to test one component. They should be short, fast, and ideally only test one thing. Often times in order to write a unit test, you may need to mock data, a component, or library. We use the library Jest to help run our Unit tests.
- To run the Jest unit tests:
npm run test
End to end tests are valuable when we do not want to mock data and run against the actual compiled app on iOS or Android. In order to run the end to end tests, we have to compile the iOS or Android app, then launch a simulator, then run tests. We use Detox a "Gray box end-to-end testing and automation library" to help with our end to end testing.
You are first required to build the tests, then you can run them:
- To build the Detox end to end tests:
npm run detox-build
- To run the Detox end to end tests:
npm run detox-test
- If you are having issues with Getting Started, please reference React Native's Documentation
- If you are running into issues communicating with
expensify.com.dev
(CORS, SSL, etc.), running viangrok
is recommended, see step 3 in Getting Started
- If running on the iOS simulator pressing
βD
will open the debugging menu. - This will allow you to attach a debugger in your IDE, React Developer Tools, or your browser.
- For more information on how to attach a debugger, see React Native Debugging Documentation
Our React Native Android app now uses the Hermes
JS engine which requires your browser for remote debugging. These instructions are specific to Chrome since that's what the Hermes documentation provided.
- Navigate to
chrome://inspect
- Use the
Configure...
button to add the Metro server address (typicallylocalhost:8081
, check yourMetro
output) - You should now see a "Hermes React Native" target with an "inspect" link which can be used to bring up a debugger. If you don't see the "inspect" link, make sure the Metro server is running.
- You can now use the Chrome debug tools. See React Native Debugging Hermes
- The major difference between React-Native and React are the components that are used in the
render()
method. Everything else is exactly the same. If you learn React, you've already learned 98% of React-Native. - The application uses React-Router for navigating between parts of the app.
- Higher Order Components are used to connect React components to persistent storage via Onyx.
These are the main pieces of the application.
This is a persistent storage solution wrapped in a Pub/Sub library. In general that means:
- Onyx stores and retrieves data from persistent storage
- Data is stored as key/value pairs, where the value can be anything from a single piece of data to a complex object
- Collections of data are usually not stored as a single key (eg. an array with multiple objects), but as individual keys+ID (eg.
report_1234
,report_4567
, etc.). Store collections as individual keys when a component will bind directly to one of those keys. For example: reports are stored as individual keys becauseChatLinkRow.js
binds to the individual report keys for each link. However, report actions are stored as an array of objects because nothing binds directly to a single report action. - Onyx allows other code to subscribe to changes in data, and then publishes change events whenever data is changed
- Anything needing to read Onyx data needs to:
- Know what key the data is stored in (for web, you can find this by looking in the JS console > Application > local storage)
- Subscribe to changes of the data for a particular key or set of keys. React components use
withOnyx()
and non-React libs useOnyx.connect()
. - Get initialized with the current value of that key from persistent storage (Onyx does this by calling
setState()
or triggering thecallback
with the values currently on disk as part of the connection process)
- Subscribing to Onyx keys is done using a constant defined in
ONYXKEYS
. Each Onyx key represents either a collection of items or a specific entry in storage. For example, since all reports are stored as individual keys likereport_1234
, if code needs to know about all the reports (eg. display a list of them in the nav menu), then it would subscribe to the keyONYXKEYS.COLLECTION.REPORT
.
Actions are responsible for managing what is on disk. This is usually:
- Subscribing to Pusher events to receive data from the server that will get put immediately into Onyx
- Making XHRs to request necessary data from the server and then immediately putting that data into Onyx
- Handling any business logic with input coming from the UI layer
This layer is solely responsible for:
- Reflecting exactly the data that is in persistent storage by using
withOnyx()
to bind to Onyx data. - Taking user input and passing it to an action
Almost all the code is located in the src
folder, inside it there's some organization, we chose to name directories that are
created to house a collection of items in plural form and using camelCase (eg: pages, libs, etc), the main ones we have for now are:
- components: React native components that are re-used in several places.
- libs: Library classes/functions, these are not React native components (ie: they are not UI)
- pages: These are components that define pages in the app. The component that defines the page itself should be named
<pageName>Page
if there are components used only inside one page, they should live in its own directory named after the<pageName>
. - styles: These files define styles used among components/pages
Files should be named after the component/function/constants they export, respecting the casing used for it. ie:
- If you export a constant named
CONST
it's file/directory should be named theCONST
. - If you export a component named
Text
the file/directory should be namedText
- If you export a function named
guid
the file/directory should be namedguid
. - For files that are utilities that export several functions/classes use the UpperCamelCase version ie:
DateUtils
. - HOCs should be named in camelCase like withOnyx.
- All React components should be PascalCase (a.k.a. UpperCamelCase π«).
In most cases, the code written for this repo should be platform-independent. In such cases, each module should have a single file, index.js
, which defines the module's exports. There are, however, some cases in which a feature is intrinsically tied to the underlying platform. In such cases, the following file extensions can be used to export platform-specific code from a module:
- Mobile =>
index.native.js
- iOS/Android =>
index.ios.js
/index.android.js
- Web =>
index.website.js
- Desktop =>
index.desktop.js
Note that index.js
should be the default. i.e: If you have mobile-specific implementation in index.native.js
, then the desktop/web implementation can be contained in a shared index.js
. Furthermore, index.native.js
should not be included in the same module as index.ios.js
or index.android.js
, nor should index.js
be included in the same module as index.website.js
or index.desktop.js
.
When adding new API commands (and preferably when starting using a new one that was not yet used in this codebase) always
prefer to return the created/updated data in the command itself, instead of saving and reloading. ie: if we call CreateTransaction
,
we should prefer making CreateTransaction
return the data it just created instead of calling CreateTransaction
then Get
rvl=transactionList
Different platforms come with varying storage capacities and Onyx has a way to gracefully fail when those storage limits are encountered. When Onyx fails to set or modify a key the following steps are taken:
- Onyx looks at a list of recently accessed keys (access is defined as subscribed to or modified) and locates the key that was least recently accessed
- It then deletes this key and retries the original operation
By default, Onyx will not evict anything from storage and will presume all keys are "unsafe" to remove unless explicitly told otherwise.
To flag a key as safe for removal:
- Add the key to the
safeEvictionKeys
option inOnyx.init(options)
- Implement
canEvict
in the Onyx config for each component subscribing to a key - The key will only be deleted when all subscribers return
true
forcanEvict
e.g.
Onyx.init({
safeEvictionKeys: [ONYXKEYS.COLLECTION.REPORT_ACTIONS],
});
export default withOnyx({
reportActions: {
key: ({reportID}) => `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${reportID}`,
canEvict: props => !props.isActiveReport,
},
})(ReportActionsView);
Every PR merged into master
will kick off the Create a new version GitHub workflow defined in .github/workflows/version.yml
.
It will look at the current version and increment it by one build version (using react-native-version
), create a PR with that new version, and tag the version.
The PR will be merged automatically by the GitHub workflow automerge to keep the version always up to date.
When a new tag is pushed, it will trigger a deploy of all four clients:
- The web app automatically deploys via a GitHub Action in
.github/workflows/main.yml
- The MacOS desktop app automatically deploys via a GitHub Action in
.github/workflows/desktop.yml
- The Android app automatically deploys via a GitHub Action in
.github/workflows/android.yml
- The iOS app automatically deploys via a GitHub Action in
.github/workflows/ios.yml
The GitHub workflows require a large list of secrets to deploy, notify and test the code:
LARGE_SECRET_PASSPHRASE
- decrypts secrets stored in various encrypted files stored in GitHub repository:android/app/my-upload-key.keystore.gpg
android/app/android-fastlane-json-key.json.gpg
ios/chat_expensify_appstore.mobileprovision
ios/Certificates.p12.gpg
SLACK_WEBHOOK
- Sends Slack notifications via Slack WebHook https://expensify.slack.com/services/B01AX48D7MMOS_BOTIFY_TOKEN
- Personal access token for @OSBotify user in GitHubCSC_LINK
- Required to be set for desktop code signing: https://www.electron.build/code-signing.html#travis-appveyor-and-other-ci-serversCSC_KEY_PASSWORD
- Required to be set for desktop code signing: https://www.electron.build/code-signing.html#travis-appveyor-and-other-ci-serversAPPLE_ID
- Required for notarizing desktop code indesktop/notarize.js
APPLE_ID_PASSWORD
- Required for notarizing desktop code indesktop/notarize.js
AWS_ACCESS_KEY_ID
- Required for hosting website and desktop compiled codeAWS_SECRET_ACCESS_KEY
- Required for hosting website and desktop compiled codeCLOUDFLARE_TOKEN
- Required for hosting website
Sometimes it might be beneficial to generate a local production version instead of testing on production. Follow the steps below for each client:
In order to generate a production web build, run npm run build
, this will generate a production javascript build in the dist/
folder.
In order to compile a production desktop build, run npm run desktop-build
, this will generate a production app in the dist/Mac
folder named Chat.app
.
In order to compile a production iOS build, run npm run ios-build
, this will generate a Chat.ipa
in the root directory of this project.
To build an APK to share run (e.g. via Slack), run npm run android-build
, this will generate a new APK in the android/app
folder.