Variables not working with Prisma Filters

[gmiserez]

Hi,

We've recently started using HotChocolate 9.1.0-preview.XX and its PRISMA Filters.
While the filters are mostly working great, we've noticed that we have an issue when the filters are passed as variables instead of directly in the Query.

In short, this works:

query getCitiesStartingWithP{
  cities(first:10, where:{  name_starts_with: "P"}){
    nodes{
      name
    }
  }
}

This doesn't work:

Query:

query getCitiesStartingWithP2($where: CityFilter){
  cities(first:10, where:$where){
    nodes{
      name
    }
  }
}

Variables:

{
  "where":{
    "name_starts_with": "P"
  }
}

Steps to reproduce
1- Clone demo repository from here
2- Run the Hotchocolate endpoint and test the two given queries against it

Expected behavior
Both queries should work

Obtained behavior
getCitiesStartingWithP2 returns his error:

{
  "errors": [
    {
      "message": "Unexpected Execution Error",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "cities"
      ],
      "extensions": {
        "message": "Expression of type 'System.Object' cannot be used for parameter of type 'System.String' of method 'Boolean Contains(System.String)'\r\nParameter name: arg0"
      }
    }
}

Context

• HotChocolate 9.1.0-preview.42
• Tested with Altaïr GraphQL Client

[gmiserez]

I take it it will be solved with this PR?
#960