Handle facebook login with same account used with Google using firebase - firebase

Question

I'm working on a react native project and I've came to a part where initially I implemented google sign in my project using react-native-google-signin and later on Facebook sign in using react-native-fbsdk packages with the help of firebase and both worked like a charm "individually".
The Problem
Let's say the user logged in using google account and it worked but later logged in using Facebook with the same account (I'm allowing only one email per user in firebase), I get an error
auth/account-exists-with-different-credentials
I want the user to be able to login using Facebook from the login screen or to be more specific to link his account from the login screen.
What have I tried?
I searched online and found some answers and got up with this solution or piece of code:
facebookSignin: async () => {
const result = await LoginManager.logInWithPermissions([
'public_profile',
'email',
]);
if (result.isCancelled) {
alert('User cancelled the login process');
this.setState({loginInProcess: false});
}
const data = await AccessToken.getCurrentAccessToken();
if (!data) {
alert('Something went wrong obtaining access token');
this.setState({loginInProcess: false});
}
const facebookCredential = auth.FacebookAuthProvider.credential(
data.accessToken,
);
await auth()
.signInWithCredential(facebookCredential)
// The problem starts here from the catch block
.catch((error) => {
if (
error.code === 'auth/account-exists-with-different-credential'
) {
var pendingCred = error.credential;
var email = error.email;
auth()
.fetchSignInMethodsForEmail(email)
.then(async (methods) => {
if (methods[0] === 'google.com') {
const {idToken} = await GoogleSignin.signIn();
const googleCredential = auth.GoogleAuthProvider.credential(
idToken,
);
auth()
.signInWithCredential(googleCredential)
.then((user) => {
user.linkWithCredential(pendingCred);
})
.catch((error) => console.log(error));
}
});
}
});
}
This code implements a function when triggered, if there is no user with the same email, it proceeds normally, however if there is an error (mentioned above), it will grant the user with a list of google accounts that are present in the user phone (google thing) and when he chooses his account (linked with google account) it doesn't work. The email isn't linked.
To be more specific, I would like somehow to not grant the user with all his google accounts but only with the email to be linked var email = error.email; (in the code snippet above) and for the Facebook provider to be linked successfully.

Answer 1

After a little of hard work, I've managed to make it work in react native and I'm gonna leave the answer here for peeps who are facing the same issue. Be ware that I used react-native-prompt-android to ask the user for confirming his password when trying to link with Facebook.
The user tries to sign with Facebook and gets this error:
auth/account-exists-with-different-credentials
This is how I handled it:
.catch((error) => {
// Catching the error
if (
error.code === 'auth/account-exists-with-different-credential'
) {
const _responseInfoCallback = (error, result) => {
if (error) {
alert('Error fetching data: ' + error.toString());
} else {
setEmail(result.email);
}
};
// Getting the email address instead of error.email from Facebook
const profileRequest = new GraphRequest(
'/me?fields=email',
null,
_responseInfoCallback,
);
new GraphRequestManager().addRequest(profileRequest).start();
if (email) {
auth()
.fetchSignInMethodsForEmail(email)
.then(async (methods) => {
// Checking the method
if (methods[0] === 'password') {
// Prompting the user to confirm/input his password for linking
const AsyncAlert = () => {
return new Promise((resolve, reject) => {
prompt(
'Password Confirmation',
'The email address is already linked with password account. Enter your password to process',
[
{
text: 'Cancel',
style: 'cancel',
},
{
text: 'Continue',
onPress: (password) =>
resolve(setPassword(password)),
},
],
{
type: 'secure-text',
cancelable: false,
placeholder: 'Password',
},
);
});
};
// Here the linking goes
await AsyncAlert().then(async () => {
await auth()
.signInWithEmailAndPassword(email, password)
.then(() => {
return auth().currentUser.linkWithCredential(
facebookCredential,
);
})
.catch(() => alert('Something went wrong'));
});
} else if (methods[0] === 'google.com') {
const {idToken} = await GoogleSignin.signIn(email);
const googleCredential = auth.GoogleAuthProvider.credential(
idToken,
);
await auth()
.signInWithCredential(googleCredential)
.then(() => {
return auth().currentUser.linkWithCredential(
facebookCredential,
);
});
}
});
} else {
alert('Something went wrong');
}
}
});