useFeatureFlag doesn't re-evaluate on default user change

[jacksonrayhamilton]

Describe the bug

This seems similar to: #27

The docs for the React SDK recommend setting the default user using client.setDefaultUser: https://configcat.com/docs/sdk-reference/react/#default-user

const currentUser = { identifier: 'john@example.com' };

export const SetConfigCatUserComponent = () => {
  const client = useConfigCatClient();

  const [user] = useState(currentUser);

  useEffect(() => {
    client.setDefaultUser(user);
  }, [client, user]);

  return null;
};

However, it appears that when client.setDefaultUser is called, this doesn't automatically trigger useFeatureFlag() calls throughout a React app to start recalculating their values (in case they might be different based on the new user).

To reproduce

1. Have useFeatureFlag() calls in your app that will return true if your user is X, false if not
2. Have the default user be undefined
3. Asynchronously set the default user to be user X using client.setDefaultUser
4. Observe that the useFeatureFlag() calls don't start returning true simply as a result of calling client.setDefaultUser

Expected behavior

client.setDefaultUser(), or another SDK-provided function, would integrate with React state and immediately cause useFeatureFlag() calls throughout the app to start returning proper values for the new user.

SDK version

• configcat-react: 5.0.3
• @configcat/sdk: 1.0.2

SDK configuration

import { ConfigCatProvider, useConfigCatClient } from "configcat-react";

/** Keeps the ConfigCat client's default user in sync with session */
const ConfigCatUserSync = () => {
    const client = useConfigCatClient();
    const { session } = useSessionContext();

    useEffect(() => {
        if (session) {
            client.setDefaultUser({
                identifier: String(session.idPayor),
                email: session.email ?? undefined,
                custom: { account: String(session.idAccount) }
            });
        } else {
            client.setDefaultUser({ identifier: `anonymous` });
        }
    }, [client, session]);

    return null;
};

const Navigation = () => (
    <SessionProvider>
        <ConfigCatProvider sdkKey={window.settings.CONFIGCAT_SDK_KEY}>
            <ConfigCatUserSync />
            <Router>
                <App />
            </Router>
        </ConfigCatProvider>
    </SessionProvider>
);

Logs

N/A

Language/Framework version

React

Platform

macOS 15, Chrome 145

[jacksonrayhamilton]

I'd also like to add that we were able to work around this issue by abandoning the "default user" feature, and instead managing a default ConfigCat user using React context, and passing that into useFeatureFlag as the user param using a wrapper hook. Then the work you did in #27 kicks in, and useFeatureFlag immediately returns a new value. But we think it'd be nice if this was managed at the SDK level instead!

Let me know also if this is supported somehow, and if the issue is just with how we're using the SDK.

[adams85]

Thank you for reporting the issue.

As far as I can see, you are following the example shown in the documentation, so if it doesn't work, it's very likely that this is a problem with the SDK.

Please allow us some time to look into it.

Until then, it sounds fine to use the workaround you described, i.e., to encapsulate the user into a React context and pass that into useFeatureFlag.