firebase_functions_interop 0.1.0-beta.3

Write Firebase Cloud Functions in Dart

Firebase Functions Interop Library for Dart

Write Firebase Cloud functions in Dart, run in NodeJS. This is an early preview, alpha open-source project.

• What is this?
• Status
• Usage
• Configuration

What is this?

firebase_functions_interop provides interoperability layer for Firebase Functions NodeJS client. Firebase functions written in Dart using this library must be compiled to JavaScript and run in NodeJS. Luckily, a lot of interoperability details are handled by this library and a collections of tools from Dart SDK.

Here is a minimalistic "Hello world" example of a HTTP cloud function:

import 'package:firebase_functions_interop/firebase_functions_interop.dart';

void main() {
  firebaseFunctions['helloWorld'] =
      firebaseFunctions.https.onRequest(helloWorld);
}

void helloWorld(HttpRequest request) {
  request.response.writeln('Hello world');
  request.response.close();
}

Status

This is a early preview, alpha version which is not feature complete.

Below is status report of already implemented functionality by namespace:

• ✅ functions
• ✅ functions.config
• ❌ functions.analytics
• ❌ functions.auth
• ❌ functions.firestore 🔥 (bindings only at this point)
• ✅ functions.database
• ✅ functions.https
• ❌ functions.pubsub
• ❌ functions.storage

Usage

Make sure you have Firebase CLI installed as well as a Firebase account and a test app. See Getting started for more details.

1. Create a new project directory and initialize functions:

$ mkdir myproject
$ cd myproject
$ firebase init functions

This creates functions subdirectory in your project's root which contains standard NodeJS package structure with package.json and index.js files.

2. Initialize Dart project

Go to functions subfolder and add pubspec.yaml with following contents:

name: myproject_functions
description: My project functions
version: 0.0.1

environment:
  sdk: '>=1.20.1 <2.0.0'

dependencies:
  # Firebase Functions bindings
  firebase_functions_interop: ^0.1.0-beta.1
  # Node bindings required to compile a nice-looking JS file for Node.
  # Also provides access to globals like `require` and `exports`.
  node_interop: ^0.1.0-beta.6

transformers:
  - $dart2js
  - node_interop # This transformer must go after $dart2js

Then run pub get to install dependencies.

3.1 Write a Web function

Create node/index.dart and type in something like this:

import 'package:firebase_functions_interop/firebase_functions_interop.dart';

void main() {
  firebaseFunctions['helloWorld'] =
      firebaseFunctions.https.onRequest(helloWorld);
}

void helloWorld(HttpRequest request) {
  request.response.writeln('Hello world');
  request.response.close();
}

Copy-pasting also works.

3.2 Write a Realtime Database Function (optional)

Update node/index.dart with following:

void main() {
  // ...Add after registration of helloWorld function:
  firebaseFunctions['makeUppercase'] = firebaseFunctions.database
        .ref('/messages/{messageId}/original')
        .onWrite(makeUppercase);
}

FutureOr<Null> makeUppercase(DatabaseEvent<String> event) {
  var original = event.data.val();
  print('Uppercasing $original');
  return event.data.ref.parent.child('uppercase').setValue(uppercase);
}

4. Build your function(s)

Building functions is as simple as running pub build. Note that Pub by default assumes a "web" project and only builds web/ folder so we need to explicitly tell it about node/:

$ pub build node/

5. Copy and deploy

The result of pub build is located in build/node/index.dart.js. Replace default index.js with the built version:

$ cp build/node/index.dart.js index.js

Deploy using Firebase CLI:

$ firebase deploy --only functions

6. Test it

You can navigate to the new HTTPS function's URL printed out by the deploy command. For the Realtime Database function, login to the Firebase Console and try changing values under /messages/{randomValue}/original.

Configuration

Firebase SDK provides a way to set and access environment variables from your Firebase functions.

Environment variables are set using Firebase CLI, e.g.:

firebase functions:config:set some_service.api_key="secret" some_service.url="https://api.example.com"

For more details see https://firebase.google.com/docs/functions/config-env.

To read these values in a Firebase function use firebaseFunctions.config:

import 'package:firebase_functions_interop/firebase_functions_interop.dart';
// Import 'node_interop/http' as it provides convenient HTTP client
// implementation which uses Node IO system.
import 'package:node_interop/http.dart';

void main() {
  firebaseFunctions['helloWorld'] =
      firebaseFunctions.https.onRequest(helloWorld);
}

void helloWorld(HttpRequest request) async {
  /// fetch env configuration
  var config = firebaseFunctions.config;
  var serviceKey = config.get('someservice.key');
  var serviceUrl = config.get('someservice.url');
  /// use HTTP client to make calls to external systems:
  var http = new NodeClient();
  var response = await http.get("$serviceUrl?apiKey=$serviceKey");
  // do something with the response, e.g. forward response body to the client:
  request.response.write(response.body);
  request.response.close();
}

Features and bugs

Please file feature requests and bugs at the issue tracker.