firebase functions emulator useFunctionsEmulator() method not working

I haven't been able to get useFunctionsEmulator() either but I have a workaround:

I switch my onCall function to an onRequest function like so:

// FROM THIS
exports.exampleFunction = functions.https.onCall((data, context) => {
  // CODE FOR CLOUD FUNCTION
});
// TO THIS
exports.exampleFunction = functions.https.onRequest((request, response) => {
  // CODE FOR CLOUD FUNCTION
});

Then I can serve my function locally with this command firebase serve --only functions which will display a url that I can send requests to via curl, postman or my browser. When I'm done editing the function I switch it back to an onCall function. I hope this helps!

As @app_ wrote, but also this may be worth to someone:

If you use regions, they should only be set for the online call, not the emulated one. This works for me (JavaScript client):

const fns = LOCAL ? firebase.app().functions() :
  firebase.app().functions(functionsRegion);

const log = fns.httpsCallable('logs_v200719');

The LOCAL is set earlier to true if we know we are run against emulated back-end. Please let me know if there's a standard way to sniff that, from the Firebase client.

For developer experience, it would be best if regions are handled the same way locally, meaning one doesn't need the above ternary operator.

firebase-tools 8.6.0, JavaScript client 7.16.1

I got the emulators working and handling local requests by calling the useFunctionsEmulator() method just after initializing the firebase app in the client. Calling it prior caused errors.

firebase.initializeApp(config);
firebase.functions().useFunctionsEmulator("http://localhost:5001");

useFunctionsEmulator() doesn't return anything, it's just a setter.

Use it in the following way:

firebase.initializeApp(config);

const functions = firebase.functions();
functions.useFunctionsEmulator("http://localhost:5001");