Fields asked in queries are not always in the response, depending on their order

[vparpoil]

I just ran into what seems to be a bug :

Those two queries don't give the same result, query 1 will return the authorId, but query2 won't (it will though be present in author._id)

    let grapherQueryOne = createQuery('grapherQueryOne', {
        Book: {
            name: 1,
            authorId: 1,
            author: {
                name: 1,
            },
        }
    });

    let grapherQueryTwo = createQuery('grapherQueryTwo', {
        Book: {
            name: 1,
            author: {
                name: 1,
            },
            authorId: 1,
        }
    });

Here is a reproduction : https://github.com/vparpoil/grapher-bug-in-fields-returned/blob/master/server/main.js

[theodorDiaconu]

Nice. This is because when author is read, then it puts into the graph the field "authorId" is needed, but it marks it as scheduled for deletion. Then when we try to add it again, it already exists so we ignore it. But this is a very good find! Curious how this was not caught up by now!

[vparpoil]

The PR referenced fixes the issue but I am not sure of the implications of the modification. Maybe it's better to change the function that is adding fields for deletion instead of tweaking the deletion itself as I proposed