graphql-php: How to handle a partial error?

Suppose we are querying a list of post:

Query {
    posts: [Post]
}

query {
    posts {
        id
        title
        body
    }
}

The requesting user does not have the read permission of some of the retrieved posts. Say if we got 10 posts, 2 of them are not allowed to be read by the requesting user (or maybe only the title field is can be read).

How can I handle such a “partial error” case?

About this issue

Original URL
State: closed
Created 6 years ago
Comments: 18 (6 by maintainers)

Most upvoted comments

If you don’t need a title, then you can just return an array with 10 entries, but have nulls in place of entries which user can’t read (since your types are defined as nullable):

[
  ['title' => 'post1'],
  null,
  ['title' => 'post3'],
  ['title' => 'post4'],
  null,
];

Also you may try returning an Exception in place of null:

[
  ['title' => 'post1'],
  new Exception('You cant read this'),
  ['title' => 'post3'],
  ['title' => 'post4'],
  new Exception('You cant read this'),
];

It will still return nulls in the final result but will also add two entries in errors section of the result.

And yet another way is to have some field defined as non-null in your Post type and then throw there:

type Post {
  title: String!
  body: String!
}

If you throw an exception in body resolver, the whole post in resulting list will be replaced with null (since post is nullable) and your error added to result errors.

vladar on Oct 25, 2018

But: I understand you have a desire to solve this differently => not arguing against it and I’m following this discussion with interest!

mfn on Oct 20, 2018

Or:

You only return 8 posts

does not have the read permission of some of the retrieved posts.

Counter-question: why are those then retrieved?

Just throwing in some perspective, suggested points 1) and 2) are perfectly valid and it really depends on your use-case.

In my casts, as I’m working with a system which also has the concept of posts, the ones the user has no permission are never returned (and if you try to get a specific post you don’t have permission it’s treated as missing).

mfn on Oct 18, 2018