```ruby
module GraphQL
  # If a field's resolve function returns a {ExecutionError},
  # the error will be inserted into the response's `"errors"` key
  # and the field will resolve to `nil`.
  class ExecutionError < GraphQL::Error
    # @return [GraphQL::Language::Nodes::Field] the field where the error occured
    attr_accessor :ast_node

    # @return [Hash] An entry for the response's "errors" key
    def to_h
      hash = {
        "message" => message,
      }
      if ast_node
        hash["locations"] = [
          {
            "line" => ast_node.line,
            "column" => ast_node.col,
          }
        ]
      end
      hash
    end
  end
end
```

Add ability to dump backtrace.
user
```ruby
module GraphQL
  # If a field's resolve function returns a {ExecutionError},
  # the error will be inserted into the response's `"errors"` key
  # and the field will resolve to `nil`.
  class ExecutionError < GraphQL::Error
    # @return [GraphQL::Language::Nodes::Field] the field where the error occured
    attr_accessor :ast_node

    # @return [Hash] An entry for the response's "errors" key
    def to_h
      hash = {
        "message" => message,
      }

      hash.merge!({ 'backtrace' => backtrace }) if self.class.backtrace_enabled

      if ast_node
        hash["locations"] = [
          {
            "line" => ast_node.line,
            "column" => ast_node.col,
          }
        ]
      end
      hash
    end

    class << self
      attr_accessor :backtrace_enabled
    end
  end
end
```
assistant