Run Firebase Callable HTTP Cloud Function locally - firebase

Question

I've a deployed a callable function, say foo, using
firebase deploy --only functions:foo
and I'm calling it in Flutter using:
var result = await FirebaseFunctions.instance.httpsCallable('foo')();
var data = result.data;
All good. But I'd like to run this function in the Firebase Emulator. When I run
firebase emulators:start --only functions
I can see the emulator up and running, and I'm connecting my Flutter app to the emulator using:
FirebaseFunctions.instance.useFunctionsEmulator('localhost', 4000);
However, I don't know how to invoke the callable foo in Flutter using the Firebase Emulator. I saw this related thread but it doesn't really answer my question.
EDIT:
Here's the console output:
✔ functions[us-central1-foo]: http function initialized (http://localhost:5001/my_project/us-central1/foo).
┌─────────────────────────────────────────────────────────────┐
│ ✔ All emulators ready! It is now safe to connect your app. │
│ i View Emulator UI at http://localhost:4000 │
└─────────────────────────────────────────────────────────────┘
┌───────────┬────────────────┬─────────────────────────────────┐
│ Emulator │ Host:Port │ View in Emulator UI │
├───────────┼────────────────┼─────────────────────────────────┤
│ Functions │ localhost:5001 │ http://localhost:4000/functions │
├───────────┼────────────────┼─────────────────────────────────┤
│ Firestore │ localhost:8080 │ http://localhost:4000/firestore │
└───────────┴────────────────┴─────────────────────────────────┘
Emulator Hub running at localhost:4400
Other reserved ports: 4500
I tried
useFunctionsEmulator('localhost', 4000);
useFunctionsEmulator('localhost', 5001);
but both of them throw the following error on calling httpsCallable('foo') but without the emulators, this function does work.
[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: [firebase_functions/unavailable] UNAVAILABLE

Answer 1

I suspect your host and port values might be incorrect.
When you start up your emulator, the logs will display all the ports that are being used for your various emulators. There's also the firebase.json file that has the port configurations for the emulators.
Also, localhost is not automatically identified by the clients. For Android you might have to configure networkSecurityConfig in your manifest by creating a network security config xml. For iOS, I think there should be something that needs to be added in the plist file - has to be checked confirmed.
Once your clients are able to access localhost (implicitly or explicitly), you can connect to your emulated functions. For example, I have explicitly state the host value in my code (this is not expected to change across restarts).
Here is the code that I use in Kotlin:
functions = FirebaseFunctions.getInstance()
/*
* Emulator
* */
if (emulatorMode) { //Local Testing
functions.useEmulator("10.0.2.2", 5001)
} else { //Live
functions = Firebase.functions
}
// Call the function and extract the operation from the result
return functions
.getHttpsCallable(function)
.call(inputData)
.continueWith { task ->...

Answer 2

It doesn't seem like a port or setup issue to me. Your console seems to show the expected output.
Try this:
Inside Flutter, where you want to call the function, add:
http.get(Uri.parse('http://localhost:5001/my_project/us-central1/foo'))
You're going to have to set an env variable, that asks your application to check what environment it is in. If dev, then it should use url above, if prod it can use the prod url

Answer 3

this._cloudFunctions = FirebaseFunctions.instance;
_cloudFunctions.useFunctionsEmulator(origin: "http://<System's IP>:5001");
Systems ip we can get by typing ipconfig in command prompt.
Make sure you connect your ip and run emulators start.

Answer 4

For Flutter
As per the Firebase Flutter Docs-
There is a useFunctionsEmulator module as part of your Firebase Functions instance.
You can initialize it as follows:
FirebaseFunctions.instance.useFunctionsEmulator('localhost', 5001);
For Web
If you cd into the functions directory you can run npm start which will, by default, build and run the emulators locally in the shell. I've found this to be the only solution for testing callable functions locally.
The firebase team has provided a connectFunctionsEmulator submodule in the V9 modular SDK which is designed specifically to interact with your app locally.
You can checkout the official docs for this Here.
Running npm run serve will serve the emulator that you are expecting but I have been running into issues testing callable functions via url.