Subscriptions async filter

[oddeirik]

I am currently in the process of migrating from Apollo Server 2.x over to graphql-yoga, which so far has been surprisingly low effort. However, there's one thing I'm currently trying to wrap my head around: subscription filters.

In our current approach we've used the withFilter function from Apollo to let us filter subscriptions, primarily to check for permissions/authorization before publishing an event.

To do that, we use an async filter function because our auth check is async. As far as I can tell, the filter function in graphql-yoga does not allow for an async filter function to be provided, so how would I best go about doing this?

It's a little hard to supply our exact implementation, but here's a pseudo example of what we're doing in one case:

const makeCampaignSubscriber = (root, args, context) => {
	return withFilter(
        () => pubsub.asyncIterator('COMMENT_ADDED'),
		// Async filter function to check if user in context has access to changed entity
        async (campaign, args) => await isAuthorized(ctx, { campaignId: campaign.id }),
      );
}

Seeing how the map function allows for an async function I can do the auth check there and pipe the payload AND the auth result to filter() and then a new map() that only returns the payload, but that seems a bit cumbersome to do.

[n1ru4l]

Hey there, you are right that the filter utility function currently does not support returning a Promise. However, nothing speaks against supporting this.

I will create an issue for tracking this.

• support async filters #2290
• feat: support returning a Promise from the filter utility function #2291