Unable to pass enum value as argument in GraphQL query

[kouma]

Hello there,

When you pass enum values as argument in your GraphQL queries, the validation fails. To reproduce this bug, let's use the super simple SortEnum that contains only 2 attributes, ASC and DESC :

enum SortEnum @doc(description: "This enumeration indicates whether to return results in ascending or descending order") {
    ASC
    DESC
}

We'll use it on the products query to sort the paginated result.

Preconditions (*)

1. Magento 2.3
2. graphql-php 0.13.0

Steps to reproduce (*)

1. Install GraphiQL extension for Chrome here
2. Set the endpoint with your site uri : https://yoursite.com/graphql
3. In the left column, type this query :

query Products(
  $price: String,
  $sort: SortEnum = DESC
) {
    products (
        filter: {
          price: {
            gt: $price
          }
        },
        sort: {
          name: $sort
        }
    ) {
      items {
        id
        name
      }
    }
  }

Type these variables in the "Query Variables" block on the bottom left :

{
  "sort": "ASC",
  "price": "1"
}

...and hit the big upper button to perform the request.

Expected result (*)

1. Normally in GraphQL, you are able to pass enum types as variables. The result should be a paginated list of products sorted by name ASC.

Actual result (*)

1. The request doesn't perform well :

{
  "errors": [
    {
      "message": "Variable \"$sort\" of type \"SortEnum\" used in position expecting type \"SortEnum\".",
      "category": "graphql",
      "locations": [
        {
          "line": 3,
          "column": 3
        },
        {
          "line": 12,
          "column": 17
        }
      ]
    }
  ]
}

I don't know if it's a Magento or a graphql-php related error. The error seems to be caused by the graphql-php validation process, the class GraphQL\Validator\Rules\VariablesInAllowedPosition is causing the error.

I tested with custom enums and the issue is the same. The only way to succeed is to change the type SortEnum to String and pass value as a string, but it's not a proper solution at all.
Actually this is very annoying because you can't use enum types as arguments for queries.

[naydav]

Fixed and merged in
#259

[kouma]

Hey thank you for your time !