useIdTokenResult fires a redundant token fetch on every re-render

[tyler-reitz]

Problem

useIdTokenResult constructs its observable source eagerly:

const observable$ = from(user.getIdTokenResult(forceRefresh));

from(promise) is called at hook-render time, so every re-render that doesn't hit the observable cache fires a discarded getIdTokenResult network request. This is the same pattern fixed in useStorageDownloadURL by #735.

Fix

Wrap in defer() so the promise is constructed at subscription time, not render time:

const observable$ = defer(() => user.getIdTokenResult(forceRefresh));

Related

• fix: surface observable errors via status instead of re-throwing #735 fixed the same pattern in useStorageDownloadURL
• useCallableFunctionResponse has a more severe variant (see useCallableFunctionResponse invokes the cloud function on every re-render #744)