Query with variables return null

[kejoRx]

const typeDefs = `
    type Item  {
        id: ID!
        sku: String!
        name: String!
        attribute_set_id: Int!
        price: Float
        status: Int!
        visibility: Int!
        type_id: String!
        created_at: String!
        updated_at: String!
        product_links: [String]
        tier_prices: [Int]
        custom_attributes: [CUSTOM_ATTRIBUTES]
    }
        
    union CUSTOM_ATTRIBUTES = CustomString | CustomArray
    
   type CustomString {
    attribute_code: String
    value: String
  }
  
  type CustomArray {
    attribute_code: String
    value: [String]
    
  } 

  type Query {
    allItems(value: [String]!): [Item]!
    
  }
`;

Resolver func

export const resolvers = {
    Query: {
        allItems: (_, { value }) => getAllLinks().then(result => filter(result, {value: value}))
        //allItems: () => getAllLinks(),

    },

Graphiql query:

query FetchItems($values : [String]!){
  allItems(value : $values){
    id
    name
    custom_attributes{
      __typename
      ... on CustomString{
        attribute_code
        valString: value
      }
      ... on CustomArray{
        attribute_code
        valArray: value
      }
    }
  }
}

Query Variables:

{
  "values": ["3"]
}

Output:

{
  "data": {
    "allItems": []
  }
}

It should return items that have "3" (or any other number) as string in value in typename CustomArray (that's where is category_ids), but it returns null. Why?

This is the first item in api:

{
                "id": 1,
                "name": "Some name",
                "some others" : "that not matter"
                "custom_attributes": [
                    {
                        "attribute_code": "description",
                        "value": "<p>Here's is description</p>"
                    },
                    {
                        "attribute_code": "image",
                        "value": "/m/b/mb01-blue-0.jpg"
                    },
                    {
                        "attribute_code": "small_image",
                        "value": "/m/b/mb01-blue-0.jpg"
                    },
                    {
                        "attribute_code": "thumbnail",
                        "value": "/m/b/mb01-blue-0.jpg"
                    },
                    {
                        "attribute_code": "category_ids",
                        "value": [
                            "3",
                            "4"
                        ]
                    },
                    {
                       "some others" : "that not matter as well"
                    },
                   
                ]
            },

[IvanGoncharov]

We want to keep signal strong in the GitHub issue tracker – to make sure that it remains the best place to track bugs and features that affect development.

If you have a question on how to use GraphQL, please post it to Stack Overflow with the tag #graphql.

@kejoRx Please consider posting your question to Stack Overflow.
If you think it's caused by some bug in graphql-js please provide a minimal example with all code involved.