useQuery sometimes doesn't start polling when skip is set to true

Intended outcome:

In code like this:

 useQuery(QUERY_FOR_POLL, {
    variables,
    pollInterval: 10000, // 10s
    skip,
  });

Polling should start when skip is set to false.

Actual outcome:

Sometimes polling won’t start. It usually happens after starting and then stopping query.

How to reproduce the issue:

Codesandbox I added console.log to the link, so you can check if polling is working. If you click multiple times on the button, it will stop working.

Possible workaround:

I added key to the outer component which will make all hooks lose saved state, and it can work for my use case, but I think that I maybe added one edge case bug to my app.

Versions

  System:
    OS: macOS 11.1
  Binaries:
    Node: 14.13.0 - /usr/local/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.8 - /usr/local/bin/npm
  Browsers:
    Edge: 88.0.705.63
    Safari: 14.0.2
  npmPackages:
    @apollo/client: ^3.3.0 => 3.3.1 
    apollo-upload-client: ^14.1.3 => 14.1.3 

[iamdiogo]

@jcreighton When would it be possible to have updates on this?

Having skip end up stop working is a bit of a deal-breaker

[iamdiogo]

On a first (quick) look, it seems to be related to this line:

    if (skip || query !== this.previous.query) {  // <-- this one
      this.removeQuerySubscription();
      this.removeObservable(!skip);
      this.previous.query = query;
    }

As skip is turned back to false, the query subscription and observable aren’t removed. Given that, further on this code, startQuerySubscription first checks if a subscription already exists, and returns directly if there is one, this could be the reason, as it wasn’t removed by not entering the above condition.