Meteor.publish with call to an async function returning error

Question

I am trying to create a wrapper method for Meteor.publish that does an access check before actually calling it.

The access check is represented by an async-await method, which leads to the following error in my wrapper function when running it, if I convert my wrapper method to an async one.

Exception from sub alerts.notAcknowledged id 2 Error: Publish function can only return a Cursor or an array of Cursors at Subscription._publishHandlerResult (packages/ddp-server/livedata_server.js:1132:18)

If I remove the async keyword from the wrapper method and comment out the call to the async-await method, the wrapper method is working as expected.

Answer 1

I did not find any answer to solve my issue, but after checking several solutions and trying out, I got to the following solution:

export const wrapperPublish = (metadata: any, callback: Function) => {
     Meteor.publish(metadata.name, (params: LooseObject) => {

        const allowAccessSync = Meteor.wrapAsync(allowAccess);
        const { error, hasAccess } = MeteorPromise.await(allowAccessSync({
                                     token: params.token,
                                     methodName: params.methodName,
                                     }, () => {}));
        check(params, metadata.checks);
        if (!hasAccess) {
            // do something 
        }

        return callback(params);
    });
};

In the code snippet above, the allowAccess represents the function returning a Promise and the solution was the Meteor.wrapAsync that transforms an async function into a convenient synchronous-looking function. https://docs.meteor.com/api/core.html#Meteor-wrapAsync