Entity resolvers should support partial responses and errors combined

[SvenW]

Right now I can't find a way for entity resolvers to return both partial responses and the errors to the entities that wasn't resolved.

So either I get

{
  "data": null,
  "errors": [
    {
      "message": "Not found James",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "_entities",
        1
      ]
    }
  ]
}

or I can get

{
  "data": {
    "_entities": [
      {
        "__typename": "Character",
        "name": "James Holden"
      },
      null
    ]
  }
}

by just capturing all errors.
I opened this PR just to get some guidance and to see if you have any input, thanks.

[paulpdaniels]

I'll look into this, AFAICR it shouldn't be doing anything special wrt to partial resolution, I'm wondering if we even support partial array failures in general 🤔

[SvenW]

So I took a little bit of time yesterday just to see what happens here. It seems that for EntityResolvers we end up here https://github.com/ghostdogpr/caliban/blob/series/2.x/core/src/main/scala/caliban/execution/Executor.scala#L146. Shouldn't these types of steps be liststeps? I can of course solve the issue with some sort of hack here and use handleError. Do you have any pointers?

[SvenW]

So I took a little bit of time yesterday just to see what happens here. It seems that for EntityResolvers we end up here https://github.com/ghostdogpr/caliban/blob/series/2.x/core/src/main/scala/caliban/execution/Executor.scala#L146. Shouldn't these types of steps be liststeps? I can of course solve the issue with some sort of hack here and use handleError. Do you have any pointers?

I looked at the spec for _Entity and noticed it was NON_NULL which caused the Executor to handle it in a faulty way where the items in a ListStep couldn't be nullable thus returning only the errors instead of a partially resolved response.

[frekw]

LGTM 👍

[ghostdogpr]

LGTM! @paulpdaniels wanna double check?

[paulpdaniels]

Easy fix nice!