All Web- and ServiceWorkers reliably destroyed by new `cognito-identity-js`

Describe the bug With the introduction of isomorphic-unfetch to amazon-cognito-identity-js/src/Client.js at https://github.com/aws-amplify/amplify-js/blob/7cbed47cb2bbbc3a94a6fcae87efee80a5542f2e/packages/amazon-cognito-identity-js/src/Client.js#L1 any Service Worker or Web Worker making API calls will crash with a window not found. Moreover, the inclusion of file in a JS bundle instantly destroys the browser’s Worker environment, with other fatal exceptions soon to follow.

This is because isomorphic-unfetch depends on unfetch, which fails to check for self (i.e., a Worker environment), and, thereby, replaces the Worker environment’s built-in fetch implementation with a fetch polyfill that, incorrectly, assumes window is present. https://github.com/developit/unfetch/issues/104

To fully appreciate the severity of this bug, consider that that the standardized worker implementation of the fetch spec (in Chrome it’s >> 100,000 lines, and includes proxying, cacheing, etc) is replaced by a 500 line polyfill the moment the worker loads the Amplify JS bundle, and executes import "isomorphic-unfetch".

Unfortunately, theunfetch project is not actively maintained, with a straightforward PR to fix the problem being outstanding almost 2 years: https://github.com/developit/unfetch/pull/109

The problem CAN be fixed without impacting any other Amplify code by either: 1. replacing unfetch with a fetch polyfill that correctly detects all environments, OR 2. checking for self on the 1st line of Client.js, and, if a Worker is detected, not importing isomorphic-fetch and overwriting the Worker global namespace

---

To Reproduce Based on the self-evident nature of the problem and its documentation in the isomorphic-unfetch/unfetch repo, reproducing the behavior in a Worker using Amplify should not be necessary… but, if our process nonetheless requires reproducing, do this:

From within a Web or Service Worker, call any method in @aws-amplify/auth (which will, in turn invoke amazon-cognito-identity-js/src/Client.js) or any other Amplify function dependent on @aws-amplify/auth.

The /amazon-cognito-identity-js/__tests__/ does not currently consider workers (nor SSR). Similarly, there is no testing for authentication in workers in core… all of which explains why this problem wasn’t previously identified.

To configure a worker to use Auth, you’ll need to provide an implementation of a the ICognitoStorage interface with your Config with something like:

Auth.configure({
  storage: AuthStorage,
});

The custom storage interface is required because workers don’t support LocalStorage, Amplify’s default store. Numerous examples for memory and IndexedDB stores can be found with a Google search.

[bebraw]

For reference, it looks like https://github.com/supabase/postgrest-js/pull/109 moved to use cross-fetch which doesn’t appear to have the issue when run within workers so using that over the current solution is one option.

[github-actions[bot]]

This issue has been automatically locked since there hasn’t been any recent activity after it was closed. Please open a new issue for related bugs.

Looking for a help forum? We recommend joining the Amplify Community Discord server *-help channels or Discussions for those types of questions.