How do I extend the AuthError error class

[monsterooo]

hi, I want to make a custom AuthError to verify that the user has email authentication, so I'll write it like this

next-auth version 5.beta

export class EmailVerificationError extends AuthError {
  static type = "EmailVerificationError";
}
export const {
  handlers: { GET, POST },
  auth,
  signIn,
  signOut,
  update,
} = NextAuth({
  pages: {
    signIn: "/login",
  },
  callbacks: {
    async signIn({ user, account }) {
      // ...

      // throw EmailVerificationError
      if (!existingUser?.emailVerified) {
        throw new EmailVerificationError("Email not verified!");
      }
      return true;
    },
  ...authOptions,
});

try {
    await signIn("credentials", {
      email,
      password,
      redirectTo: callbackUrl || DEFAULT_LOGIN_REDIRECT,
    });
  } catch (error) {
    if (error instanceof AuthError) {
      switch (error.type) {
        case "CredentialsSignin":
          return { error: "Invalid credentials!" };
        // The typescript error is reported here
        case "EmailVerificationError":
          return { error: "Email not verified!" };
        default:
          return { error: "Something went wrong!" };
      }
    }

    throw error;
  }

Then my nextjs action is written like this, where the case "EmailVerificationError" will cause a type mismatch problem

Has anyone experienced this problem? thank you.

[michal-bryk]

Hey,

I had similar issue but I've solved it in slightly different way: by throwing Error with different ErrorType.
It seems that whenever you throw an error in authorize it will always be CallbackRouteError, but you can set custom cause with error of custom type.

export const { auth, signIn, signOut } = NextAuth({
  ...authConfig,
  providers: [
    Credentials({
      async authorize(credentials) {
        ...
        const { email, password } = parsedCredentials.data;
        const user = await getUser(email);
        if (!user) {
          return null;
        }

        const passwordsMatch = password === user.password;
        if (!passwordsMatch) {
          return null;
        }

        // only active users allowed
        if (!user.isActive) {
          throw new Error('User not activated', {
            cause: { type: 'Verification' }, // choose one of ErrorType
          });
        }

        return user;
      },
    }),
  ],
});

then in error handler:

try {
    await signIn('credentials', formData);
  } catch (error) {
    if (error instanceof AuthError) {
      if (error.cause?.type === 'Verification') {
        return 'User not activated';
      }

      switch (error.type) {
        case 'CredentialsSignin':
          return 'Invalid credentials';
        default:
          return 'Something went wrong';
      }
    }
    throw error;
  }

Hope that helps.