Changes to logout and cache synchronicity

[stevehobbsdev]

Description

This PR makes the following changes around logout and caching:

• logout can now optionally return a Promise. This is currently the case when a custom cache implementation is specified using the cache option
• If no custom cache implementation is used, logout acts synchronously and does not return a promise
• ICache methods (get, set, remove, allKeys) can now optionally return a promise or a static value, and is handled seamlessly
• docs updated
• internal caches changed to return static values, instead of wrapping them in Promise.resolve

The motivation was for SDKs like auth0-angular and auth0-react who update their internal state reactively can now rely on logout being synchronous by default, and update their state accordingly.

Note that none of this should be a breaking change for consumers:

• If anyone already has a custom cache and are returning a Promise, that will continue to work
• Up until now, logout never returned a value so there was nothing to handle

Testing

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not master

[lgtm-com]

This pull request introduces 1 alert when merging c31598a into ecafb37 - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[adamjmcgrath]

Perhaps we should do:

const maybePromise = this.cacheManager.clear();
if (typeof maybePromise?.then === 'function') {
  return maybePromise.then(postCacheClear)
}
postCacheClear();

Then the advice would be If you provide an async cache ...

[stevehobbsdev]

Sounds reasonable!

[stevehobbsdev]

Diving into this, cacheManager.clear will always return a Promise; are you also suggesting removing cacheManager.clearSync?

[adamjmcgrath]

D'oh - no sorry, I forgot about clear/clearSync ignore me