@urql/exchange-auth is an exchange for the urql GraphQL client which helps handle auth headers and token refresh

Quick Start Guide

First install @urql/exchange-auth alongside urql:

yarn add @urql/exchange-auth
# or
npm install --save @urql/exchange-auth

You'll then need to add the authExchange, that this package exposes to your urql Client

import { createClient, cacheExchange, fetchExchange } from 'urql';
import { makeOperation } from '@urql/core';
import { authExchange } from '@urql/exchange-auth';

const client = createClient({
  url: 'http://localhost:1234/graphql',
  exchanges: [
    cacheExchange,
    authExchange(async utils => {
      // called on initial launch,
      // fetch the auth state from storage (local storage, async storage etc)
      let token = localStorage.getItem('token');
      let refreshToken = localStorage.getItem('refreshToken');

      return {
        addAuthToOperation(operation) {
          if (token) {
            return utils.appendHeaders(operation, {
              Authorization: `Bearer ${token}`,
            });
          }
          return operation;
        },
        willAuthError(_operation) {
          // e.g. check for expiration, existence of auth etc
          return !token;
        },
        didAuthError(error, _operation) {
          // check if the error was an auth error
          // this can be implemented in various ways, e.g. 401 or a special error code
          return error.graphQLErrors.some(e => e.extensions?.code === 'FORBIDDEN');
        },
        async refreshAuth() {
          // called when auth error has occurred
          // we should refresh the token with a GraphQL mutation or a fetch call,
          // depending on what the API supports
          const result = await mutate(refreshMutation, {
            token: authState?.refreshToken,
          });

          if (result.data?.refreshLogin) {
            // save the new tokens in storage for next restart
            token = result.data.refreshLogin.token;
            refreshToken = result.data.refreshLogin.refreshToken;
            localStorage.setItem('token', token);
            localStorage.setItem('refreshToken', refreshToken);
          } else {
            // otherwise, if refresh fails, log clear storage and log out
            localStorage.clear();
            logout();
          }
        },
      };
    }),
    fetchExchange,
  ],
});

Handling Errors via the errorExchange

Handling the logout logic in refreshAuth is the easiest way to get started, but it means the errors will always get swallowed by the authExchange. If you want to handle errors globally, this can be done using the mapExchange:

import { mapExchange } from 'urql';

// this needs to be placed ABOVE the authExchange in the exchanges array, otherwise the auth error
// will show up hear before the auth exchange has had the chance to handle it
mapExchange({
  onError(error) {
    // we only get an auth error here when the auth exchange had attempted to refresh auth and
    // getting an auth error again for the second time
    const isAuthError = error.graphQLErrors.some(
      e => e.extensions?.code === 'FORBIDDEN',
    );
    if (isAuthError) {
      // clear storage, log the user out etc
    }
  }
}),