Error paths and locations are duplicated with duplicate queries that error lazily

[juanrgon]

Describe the bug

Error paths and locations are duplicated with duplicate queries that error lazily.

I provided a simple script to reproduce this issue. It uses a simple single field schema with a dataloader that always resolves to an error:

require 'graphql'
require 'json'

class ItemLoader < GraphQL::Dataloader::Source
  def fetch(keys)
    keys.map { |key| GraphQL::ExecutionError.new("Error for #{key}") }
  end
end

class QueryType < GraphQL::Schema::Object
  field :item, String do
    argument :key, String
  end

  def item(key:)
    dataloader.with(ItemLoader).load(key)
  end
end

class Schema < GraphQL::Schema
  query QueryType
  use GraphQL::Dataloader
end

query = <<-GRAPHQL
  query {
    query0: item(key: "a")
    query1: item(key: "a")
  }
GRAPHQL

result = Schema.execute(query)
puts JSON.pretty_generate(result.to_h)

When running the above, I would expect to see the following:

{
  "errors": [
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ],
      "path": [
        "query0"
      ]
    },
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 3,
          "column": 5
        }
      ],
      "path": [
        "query1"
      ]
    }
  ],
  "data": {
    "query0": null,
    "query1": null
  }
}

but instead, I'm seeing this:

{
  "errors": [
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ],
      "path": [
        "query0"
      ]
    },
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ],
      "path": [
        "query0"
      ]
    }
  ],
  "data": {
    "query0": null,
    "query1": null
  }
}

Versions

graphql version: 2.3.9

GraphQL schema

class ItemLoader < GraphQL::Dataloader::Source
  def fetch(keys)
    keys.map { |key| GraphQL::ExecutionError.new("Error for #{key}") }
  end
end

class QueryType < GraphQL::Schema::Object
  field :item, String do
    argument :key, String
  end

  def item(key:)
    dataloader.with(ItemLoader).load(key)
  end
end

class Schema < GraphQL::Schema
  query QueryType
  use GraphQL::Dataloader
end

GraphQL query

Example GraphQL query and response (if query execution is involved)

  query {
    query0: item(key: "a")
    query1: item(key: "a")
  }

{
  "errors": [
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ],
      "path": [
        "query0"
      ]
    },
    {
      "message": "Error for a",
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ],
      "path": [
        "query0"
      ]
    }
  ],
  "data": {
    "query0": null,
    "query1": null
  }
}

Steps to reproduce

The script I provided at the beginning of this issue is all you need

Expected behavior

I expect error paths and locations for all fields to be unique per field

Actual behavior

I'm seeing error paths and locations for duplicate queries/fields duplicated, instead of being unique