A detailed guide to resolving common AWS Amplify authentication issues in React Native applications, with practical solutions and code examples.

AWS Amplify Documentation

Have you ever spent days debugging an authentication issue that seemed impossible to solve? I faced a mysterious problem with AWS Amplify authentication in a React Native application built with Expo. While the signup process worked flawlessly, the signin functionality kept throwing a vague error: “Unknown: An unknown error has occurred.” This article will guide you through the process of identifying and resolving this issue.

Understanding the Initial Setup

Before diving into the problem, let’s examine how the authentication was initially configured. The setup began with AWS Cognito integration in the configuration file:

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import { Amplify } from "aws-amplify";

export const configureAmplify = () => {
  Amplify.configure({
    Auth: {
      Cognito: {
        userPoolId: process.env.EXPO_PUBLIC_COGNITO_USER_POOL_ID!,
        userPoolClientId: process.env.EXPO_PUBLIC_COGNITO_CLIENT_ID!,
        signUpVerificationMethod: "code",
      },
    },
  });
};

This configuration looks correct at first (we have our user pool ID, client ID, and verification method correctly set up). The saying goes, “The devil is in the details,” highlighting that the small details can often introduce a significant impact.

Unraveling the Mystery

The authentication service implementation seemed straightforward:

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class AuthService {
  async signIn({ email, password }: SignInCredentials) {
    try {
      console.log("Attempting to sign in with:", email);
      const { isSignedIn, nextStep } = await signIn({
        username: email,
        password,
      });

      if (nextStep.signInStep !== "DONE") {
        throw new Error("Additional authentication steps required");
      }

      if (!isSignedIn) {
        throw new Error("Sign in failed");
      }

      return { isSignedIn, nextStep };
    } catch (error) {
      console.error("Sign in error:", error);
      throw this.handleError(error);
    }
  }
}

I could identify the root cause after a long struggle with Googling and reading documentation. The problem was the type of authentication flow was not specified. This leads to a battle to implement the correct authentication method.

The Simple Yet Powerful Solution

The fix required one small but significant change - explicitly specifying the authentication flow type in the signin method:

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const { isSignedIn, nextStep } = await signIn({
  username: email,
  password,
  options: {
    authFlowType: "USER_PASSWORD_AUTH",
  },
});

The addition points Amplify exactly which authentication flow to use which resolved the vaguous error.

Managing Authentication State

To complete the authentication implementation, we need a robust way to manage the auth state across the application. Here’s how to set up an authentication context:

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import React, { createContext, useContext, useState, useEffect } from "react";
import { getCurrentUser } from "aws-amplify/auth";

const AuthContext = createContext<AuthContextType | undefined>(undefined);

export function AuthProvider({ children }: { children: React.ReactNode }) {
  const [isAuthenticated, setIsAuthenticated] = useState(false);
  const [isLoading, setIsLoading] = useState(true);

  useEffect(() => {
    checkAuthState();
  }, []);

  const checkAuthState = async () => {
    try {
      const user = await getCurrentUser();
      setIsAuthenticated(!!user);
    } catch (err) {
      setIsAuthenticated(false);
    } finally {
      setIsLoading(false);
    }
  };

  // ... rest of the implementation
}

Essential Testing Steps

To ensure your authentication implementation works correctly:

  1. Verify your Amplify configuration has the correct credentials and user pool settings
  2. Test the complete signup flow with a new user
  3. Implement email verification if required
  4. Test signin with the specified authFlowType
  5. Verify the authentication state persists across app reloads

why this does not work… why this works…

Cheers! 🍺