TypeError in `normalize_error_paths` with federated routers

[tlubz]

We are using WunderGraph's Cosmo Router for GraphQL federation. When the resolver fails to bulk load data in an array context from a federated subgraph, the router will include an @ in the error paths for those errors, instead of an array index integer. From my research, this is semi-standard with federated routers like Cosmo and Apollo Router. When processing the response in these cases, the graphql client will fail with the following error:

TypeError: no implicit conversion of String into Integer
--
0: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:27:in `block (2 levels) in normalize_error_paths'
1: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:24:in `each'
2: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:24:in `block in normalize_error_paths'
3: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:21:in `each'
4: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:21:in `normalize_error_paths'
...

it's happening on this line in Errors.normalize_error_paths while validating the paths exist in the data:

current = current[key]

in this context, current is an array, but key is "@", which is causing a type error.

Reproducing the error:

errs_with_at = [{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", "@", "item"]}]
GraphQL::Client::Errors.normalize_error_paths({"records"=>[{"item"=>nil}]}, errs_with_at)

Expected result:

[{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", "@", "item"], "normalizedPath"=>["data", "records", "@", "item"]}]

Actual result

TypeError: no implicit conversion of String into Integer
from /Users/tlubitz/.asdf/installs/ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:27:in `block (2 levels) in normalize_error_paths'

By contrast, the same invocation works if you replace "@" with e.g. 0:

errs = [{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", 0, "item"], "normalizedPath"=>["data", "records", 0, "item"]}]
GraphQL::Client::Errors.normalize_error_paths({"records"=>[{"item"=>nil}]}, errs)

 [{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", 0, "item"], "normalizedPath"=>["data", "records", 0, "item"]}]

[tlubz]

we are using the following monkey-patch workaround for now:

module GraphQL
  class Client
    class Errors
      def self.normalize_error_paths(data = nil, errors = [])
        errors.each do |error|
          path = ['data']
          current = data
          error['path'].to_a.each do |key|
            break unless current
            break unless [current, key] in [Hash, String] | [Array, Integer]
            path << key
            current = current[key]
          end
          error['normalizedPath'] = path
        end
        errors
      end
    end
  end
end