Prevent situations where a logout can trigger unsubscribe of ready() data

[theodorDiaconu]

Flow:

• User logged out
• Subscription changed -> returned error
• Component Autorun re-rrun (because .fetch() was reactive) and .ready() and .fetch() were run in the same autorun context
• Left hanging subscription run due to memory leak

This was the fix, but I'm not sure exactly why, I leave it here to merge it later.

  const subscriptionError = new ReactiveVar();

  return withTracker((props) => {
    const query = handler(props);

    const subscriptionHandle = query.subscribe({
      onStop(err) {
        if (err) {
          subscriptionError.set(err);
        }
      },
      onReady() {
        subscriptionError.set(null);
      },
    });

    const isReady = subscriptionHandle.ready();

    return {
      isReady,
      query,
      config,
      props,
      subscriptionError,
    };
  })(dataTracker(errorTracker(QueryComponent)));
}```

```const dataTracker = withTracker(({ query, config, props, isReady, subscriptionError }) => ({
  grapher: {
    data: query.fetch(),
    isLoading: !isReady,
    error: subscriptionError,
  },
  query,
  config,
  props,
}));```

[Floriferous]

Just tried to clone this package and make these changes but it did not work.

Here's my setup:

• Layout -> query for current logged in user
  • Subcomponent -> query for data that has a firewall checking for a logged in user

When the user logs out, the subcomponent query is rerun, and the firewall throws an error, crashign the app on the client.

[theodorDiaconu]

@Floriferous it's normal for the subcomponent to re-run.

You logout -> Your subscriptions get updated. If you did not unmount the component, it may take some time before React unmounts it thus triggering unsubscribe. I would advise you to do something like history.push('/login'); Meteor.logout(), so you already unmount anything unnecessary.