How to Handle Firebase Auth exceptions on flutter

Question

I can't handle an error if the user tries to sign up using an already existing email

Future _createUser(Users user, String name, x) async {
    UserCredential result = await FirebaseAuth.instance
        .createUserWithEmailAndPassword(
            email: _emailController.text.trim(),
            password: _passwordController.text.trim());
    try {
      result;
    } on FirebaseAuthException catch (e) {
      if (e.code == 'firebase_auth/email-already-in-use') {
        final snackBarx = SnackBar(
          elevation: 0,
          behavior: SnackBarBehavior.floating,
          backgroundColor: Colors.transparent,
          content: AwesomeSnackbarContent(
            message: 'Error please log in again and try again',
            contentType: ContentType.failure,
          ),
        );
        ScaffoldMessenger.of(context)
          ..hideCurrentSnackBar()
          ..showSnackBar(snackBarx);

Answer 1

Use this function:

 static String getAuthErrorMessage(FirebaseAuthException ex) {
    if (ex.code == "invalid-verification-code") {
      return "Invalid OTP";
    } else if (ex.code == "code-expired") {
      return "Code expired. Try again with new code";
    } else if (ex.code == "internal-error") {
      return "Unknown error. Please try again after sometime";
    } else if (ex.code == "invalid-phone-number") {
      return "Invalid phone number";
    } else if (ex.code == "invalid-verification-id") {
      return "Invalid verification id";
    } else if (ex.code == "quota-exceeded") {
      return "We are receiving too many requests. Please try again after sometime";
    } else if (ex.code == "timeout") {
      return "Timeout. Please verify again";
    } else if (ex.code == "too-many-requests") {
      return "We are receiving too many requests. Try again after sometime";
    }

    return ex.message.toString();
  }

Use it as:

 void signInWithPhone(PhoneAuthCredential credential) async {
    try {
      UserCredential userCredential =
          await _auth.signInWithCredential(credential);
    } on FirebaseAuthException catch (ex) {
      print(getAuthErrorMessage(ex));      //👈 You can print or send a toast message
    }
  }

---

Edit: List of all the auth codes

use error code after auth/ i.e admin-restricted-operation , argument-error...

readonly ADMIN_ONLY_OPERATION: "auth/admin-restricted-operation";
    readonly ARGUMENT_ERROR: "auth/argument-error";
    readonly APP_NOT_AUTHORIZED: "auth/app-not-authorized";
    readonly APP_NOT_INSTALLED: "auth/app-not-installed";
    readonly CAPTCHA_CHECK_FAILED: "auth/captcha-check-failed";
    readonly CODE_EXPIRED: "auth/code-expired";
    readonly CORDOVA_NOT_READY: "auth/cordova-not-ready";
    readonly CORS_UNSUPPORTED: "auth/cors-unsupported";
    readonly CREDENTIAL_ALREADY_IN_USE: "auth/credential-already-in-use";
    readonly CREDENTIAL_MISMATCH: "auth/custom-token-mismatch";
    readonly CREDENTIAL_TOO_OLD_LOGIN_AGAIN: "auth/requires-recent-login";
    readonly DEPENDENT_SDK_INIT_BEFORE_AUTH: "auth/dependent-sdk-initialized-before-auth";
    readonly DYNAMIC_LINK_NOT_ACTIVATED: "auth/dynamic-link-not-activated";
    readonly EMAIL_CHANGE_NEEDS_VERIFICATION: "auth/email-change-needs-verification";
    readonly EMAIL_EXISTS: "auth/email-already-in-use";
    readonly EMULATOR_CONFIG_FAILED: "auth/emulator-config-failed";
    readonly EXPIRED_OOB_CODE: "auth/expired-action-code";
    readonly EXPIRED_POPUP_REQUEST: "auth/cancelled-popup-request";
    readonly INTERNAL_ERROR: "auth/internal-error";
    readonly INVALID_API_KEY: "auth/invalid-api-key";
    readonly INVALID_APP_CREDENTIAL: "auth/invalid-app-credential";
    readonly INVALID_APP_ID: "auth/invalid-app-id";
    readonly INVALID_AUTH: "auth/invalid-user-token";
    readonly INVALID_AUTH_EVENT: "auth/invalid-auth-event";
    readonly INVALID_CERT_HASH: "auth/invalid-cert-hash";
    readonly INVALID_CODE: "auth/invalid-verification-code";
    readonly INVALID_CONTINUE_URI: "auth/invalid-continue-uri";
    readonly INVALID_CORDOVA_CONFIGURATION: "auth/invalid-cordova-configuration";
    readonly INVALID_CUSTOM_TOKEN: "auth/invalid-custom-token";
    readonly INVALID_DYNAMIC_LINK_DOMAIN: "auth/invalid-dynamic-link-domain";
    readonly INVALID_EMAIL: "auth/invalid-email";
    readonly INVALID_EMULATOR_SCHEME: "auth/invalid-emulator-scheme";
    readonly INVALID_IDP_RESPONSE: "auth/invalid-credential";
    readonly INVALID_MESSAGE_PAYLOAD: "auth/invalid-message-payload";
    readonly INVALID_MFA_SESSION: "auth/invalid-multi-factor-session";
    readonly INVALID_OAUTH_CLIENT_ID: "auth/invalid-oauth-client-id";
    readonly INVALID_OAUTH_PROVIDER: "auth/invalid-oauth-provider";
    readonly INVALID_OOB_CODE: "auth/invalid-action-code";
    readonly INVALID_ORIGIN: "auth/unauthorized-domain";
    readonly INVALID_PASSWORD: "auth/wrong-password";
    readonly INVALID_PERSISTENCE: "auth/invalid-persistence-type";
    readonly INVALID_PHONE_NUMBER: "auth/invalid-phone-number";
    readonly INVALID_PROVIDER_ID: "auth/invalid-provider-id";
    readonly INVALID_RECIPIENT_EMAIL: "auth/invalid-recipient-email";
    readonly INVALID_SENDER: "auth/invalid-sender";
    readonly INVALID_SESSION_INFO: "auth/invalid-verification-id";
    readonly INVALID_TENANT_ID: "auth/invalid-tenant-id";
    readonly MFA_INFO_NOT_FOUND: "auth/multi-factor-info-not-found";
    readonly MFA_REQUIRED: "auth/multi-factor-auth-required";
    readonly MISSING_ANDROID_PACKAGE_NAME: "auth/missing-android-pkg-name";
    readonly MISSING_APP_CREDENTIAL: "auth/missing-app-credential";
    readonly MISSING_AUTH_DOMAIN: "auth/auth-domain-config-required";
    readonly MISSING_CODE: "auth/missing-verification-code";
    readonly MISSING_CONTINUE_URI: "auth/missing-continue-uri";
    readonly MISSING_IFRAME_START: "auth/missing-iframe-start";
    readonly MISSING_IOS_BUNDLE_ID: "auth/missing-ios-bundle-id";
    readonly MISSING_OR_INVALID_NONCE: "auth/missing-or-invalid-nonce";
    readonly MISSING_MFA_INFO: "auth/missing-multi-factor-info";
    readonly MISSING_MFA_SESSION: "auth/missing-multi-factor-session";
    readonly MISSING_PHONE_NUMBER: "auth/missing-phone-number";
    readonly MISSING_SESSION_INFO: "auth/missing-verification-id";
    readonly MODULE_DESTROYED: "auth/app-deleted";
    readonly NEED_CONFIRMATION: "auth/account-exists-with-different-credential";
    readonly NETWORK_REQUEST_FAILED: "auth/network-request-failed";
    readonly NULL_USER: "auth/null-user";
    readonly NO_AUTH_EVENT: "auth/no-auth-event";
    readonly NO_SUCH_PROVIDER: "auth/no-such-provider";
    readonly OPERATION_NOT_ALLOWED: "auth/operation-not-allowed";
    readonly OPERATION_NOT_SUPPORTED: "auth/operation-not-supported-in-this-environment";
    readonly POPUP_BLOCKED: "auth/popup-blocked";
    readonly POPUP_CLOSED_BY_USER: "auth/popup-closed-by-user";
    readonly PROVIDER_ALREADY_LINKED: "auth/provider-already-linked";
    readonly QUOTA_EXCEEDED: "auth/quota-exceeded";
    readonly REDIRECT_CANCELLED_BY_USER: "auth/redirect-cancelled-by-user";
    readonly REDIRECT_OPERATION_PENDING: "auth/redirect-operation-pending";
    readonly REJECTED_CREDENTIAL: "auth/rejected-credential";
    readonly SECOND_FACTOR_ALREADY_ENROLLED: "auth/second-factor-already-in-use";
    readonly SECOND_FACTOR_LIMIT_EXCEEDED: "auth/maximum-second-factor-count-exceeded";
    readonly TENANT_ID_MISMATCH: "auth/tenant-id-mismatch";
    readonly TIMEOUT: "auth/timeout";
    readonly TOKEN_EXPIRED: "auth/user-token-expired";
    readonly TOO_MANY_ATTEMPTS_TRY_LATER: "auth/too-many-requests";
    readonly UNAUTHORIZED_DOMAIN: "auth/unauthorized-continue-uri";
    readonly UNSUPPORTED_FIRST_FACTOR: "auth/unsupported-first-factor";
    readonly UNSUPPORTED_PERSISTENCE: "auth/unsupported-persistence-type";
    readonly UNSUPPORTED_TENANT_OPERATION: "auth/unsupported-tenant-operation";
    readonly UNVERIFIED_EMAIL: "auth/unverified-email";
    readonly USER_CANCELLED: "auth/user-cancelled";
    readonly USER_DELETED: "auth/user-not-found";
    readonly USER_DISABLED: "auth/user-disabled";
    readonly USER_MISMATCH: "auth/user-mismatch";
    readonly USER_SIGNED_OUT: "auth/user-signed-out";
    readonly WEAK_PASSWORD: "auth/weak-password";
    readonly WEB_STORAGE_UNSUPPORTED: "auth/web-storage-unsupported";
    readonly ALREADY_INITIALIZED: "auth/already-initialized";

Answer 2

In my application I handle like this:

try {
  result;
} on FirebaseAuthException catch (error) {
  if (error.code == "wrong-password") {

    //Handle error from Wrong Password

  } else if (error.code == "user-not-found") {

    //Handle error User Not Found

  } else if (error.code == "invalid-email") {
    
    //Handle error from Invalid Email

  } else if (error.code == "too-many-requests") {

    //Handle error from Too Many Requests        

  } else if (error.code == "network-request-failed") {
    
    //Handle error from NetWork failure

  }
}